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Conceptual Understanding 
 

1. Name the simplest hydrocarbon.   (2 Marks)

A: The simplest hydrocarbon is Methane (CH₄).

 

2. What are the general molecular formulae of alkanes, alkenes, and alkynes?     (2 Marks)

A: The general molecular formulae of

      a) Alkanes is C_nH_2n+2

      b) Alkenes is C_nH_2n

      c) Alkynes is C_nH_2n-2
 

3. Name the carboxylic acid used as a preservative.    (1 Mark)

A: Ethanoic acid (Acetic acid) is used as a preservative. (Acetic acid: CH₃COOH)
 

4. Name the product other than water formed on burning Ethanol in air.   (2 Marks)

A: Ethanol (or) Ethyl alcohol (C₂H₅OH) when burnt in air produces Carbon dioxide and water.

     C₂H₅OH + 3 O₂ →  2 CO₂ + 3 H₂O + Energy

5. Give the IUPAC name of the following compounds. If more than one compound is possible name all of them. (4 Marks)
i) An aldehyde derived from Ethane
ii) A ketone derived from Butane
iii) A chloride derived from Propane
iv) An alcohol derived from Pentane.                                                                              
A: i) C₂H₆ →  CH₃CHO
        Ethane           Ethanol
ii) C₄H₁₀  → CH₃COCH₃ + CH₃COCH₂CH₃
     Butane            Propanone         Butanone           

6. A mixture of Oxygen and Ethyne is burnt for welding. Can you tell why a mixture of Ethyne and air is not used?    (2 Marks)
A: ‣ Air is a mixture of many gases like N₂, CO₂, Oxygen etc.
‣ The heat and temperature produced by an acytelene flame depend upon the Oxygen used to burn it.
‣ When a mixture of air and Acetylene (Ethyne) is burnt, the amount of Oxygen available to burn is relatively less compared to the availability of Oxygen when the mixture of Oxygen and ethyne are burnt.
‣ When Ethyne is burnt in pure Oxygen, the flame temperature may be as high as 3166^oC. This temperature is sufficient to weld steel.
‣ When air and Ethyne is burnt, the flame temperature may be as high as 2200^oC which is not hot enough to weld steel. It may be sufficiently hot to weld aluminium, braze plumbing mixtures etc.
‣ So a mixture of Oxygen and Ethyne is only burnt.

7. Explain with the help of a chemical equation how an addition reaction is used in vegetable ghee industry?     (2 Marks)
A: ‣ Hydrogenation of oils converts fat in vegetable ghee industry.
‣ During this addition reaction unsaturated fatty acids (contain = bond) are converted into saturated fatty acids (contain single bond).

‣ Due to the presence of double bonds, vegetable oils undergo addition of Hydrogen just like alkenes to form saturated products called vegetable ghee which is solid at room temperature.

8. a) What are the various possible structural formulae of a compound having molecular formula C₃H₆O?
b) Give the IUPAC names of the above possible compounds and represent them in structures.
c) What is the similarity in these compounds?     (4 Marks)
A: a) Various possible structural formulae of C₃H₆O.
1) CH₃CH₂CHO  Ethanal        2) CH₃COCH₃ - Propanone
       Ethanal                                        (Propanone)
b) Structures: - IUPAC names

c) * Both the compounds are having the same molecular formula.
* Both the compounds are having 2 sp³ hybridised carbons and one 'sp²' hybridised carbon atom.
* Both the compounds contain carbonyl functional group  
* The two compounds have similar chemical properties.
 

9. Name the simplest ketone and write its molecular formula.   (1 Mark)
A: ¤ The simplest ketone is acetone.

¤ Its IUPAC name is: 2 - propanone.

10. What do we call the self linking property of carbon?      (1 Mark)
A: The self linking property of carbon is called "catenation".

11. Name the compound formed by heating ethanol at 443 K with excess of conc. H₂SO₄.     (1 Mark)
A: The Name of the compound formed by heating ethanol at 443 K with excess of conc. H₂SO₄ is Ethene.

12. Give an example for esterification reaction?   (2 Marks)
A: ¤ Ethyl alcohol reacts with ethanoic acid in the presence of conc. sulphuric acid to form ethyl acetate an ester with sweet odour.

13. Name the product obtained when ethanol is oxidised by either chromic anhydride or alkaline potassium permanganate.    (2 Marks)
A: ¤ Ethanoic acid is the product obtained.

14. Write the chemical equation representing the reaction of preparation of Ethanol from Ethane.    (2 Marks)
A: C₂H₆ + H₂O   →    C₂H₅OH + H₂  ↑ 
      Ethane                       (Ethanol) (Ethyl Alcohol)
 

15. Write the IUPAC name of the next homologous of CH₃OHCH₂CH₃.    (1 Mark)
A: ¤ Normally successive homologous differ by 1 carbon and 2 hydrogen atoms.
¤ So the next homologous of CH₃OHCH₂CH₃ is CH₃OHCH₂CH₂CH₃.

16. Define homologous series of carbon compounds. Mention any two characteristics of homologous series.      (2 Marks)
A: Homologous series: A homologous series is a group of organic compounds having similar structures and properties in which the successive compounds differ by CH₂ group.
Characteristics of homologous series:
¤ They have one general formula: C_nH_{2n + 2} & C_nH_{2n - 2} etc.,
¤ Successive compounds in the series possess a difference of -CH₂ unit.
¤ They show a regular gradation in their physical properties.
¤ They possess similar chemical properties due to same functional group.
     e.g.: Alcohols -OH group
 

17. Give the names of functional groups. i) -CHO    ii)-C = O   (1 Mark)
A: i) -CHO: This is aldehyde functional group.
     ii) -C = O: This is ketone functional group.

18. Why does Carbon form compounds mainly by covalent bonding?   (2 Marks)
A: ¤ Carbon is tetravalent. It has 4 electrons in its valency shell.
¤ The formation of C⁴⁺ ion by losing 4 electrons is very difficult.
¤ The formation of C^4- ion by gaining 4 electrons is also impossible.
¤ So Carbon has to form four covalent bonds either with its own atom or atoms of other elements.

19. Allotropy is a property shown by which class substance; elements, compounds or mixtures? Explain allotropy with suitable examples?    (4 Marks)
A: Allotropy is a property of the elements.
Allotropy: The property of an element to exist in two or more physical forms having more or less chemical properties but different physical properties is called allotropy.
¤ Carbon has many allotropes.
a) Amorphous forms b) crystalline forms c) Nano tubes
Amorphous forms: Coal, coke, wood charcoal, animal charcoal, sugar charcoal, lamp black, gas Carbon, petroleum coke are the different allotropes of carbon.
Crystalline forms: Diamond, graphite, Buckminster fullerene (₆₀C) are the different allotropes of Carbon in crystalline form.
¤ Nano tubes are sheets rolled into cylinders.

20. Explain how sodium ethoxide is obtained from Ethanol? Give chemical equations. (2 Marks)
A: ¤ Ethanol reacts with sodium to liberate Hydrogen and form Sodium ethoxide.
¤ 2 C₂H₅OH + 2 Na → 2 C₂H₅ONa + H₂
      (Ethanol)                     (Sodium Ethoxide)

21. Describe with a chemical equation how ethanoic acid may be obtained from ethanol.        (2 Marks)
A: ¤ When ethanol is heated with alkaline potassium permanganate solution (or) acidified potassium dichromate solution, it gets oxidised to form ethanoic acid.

22. Explain the cleansing action of soap.   (4 Marks)
A: ¤ Soaps and detergents make oil and dirt present on the cloth come out into water; there by making the cloth clean.
¤ Soap has one polar end and one non-polar end.
¤ The polar end is hydrophilic in nature and this end is attracted towards water.
¤ The non polar end is hydrophobic, in nature and it is attracted towards grease or oil on the cloth, but not attracted towards water.
¤ When soap is dissolved in water, its hydrophobic ends attach themselves to dirt and remove it from the cloth.
¤ The hydrophobic end of the soap molecules move towards the dirt or grease particles.
¤ The hydrophobic ends attached to the dirt particle and try to pull out.
¤ The molecules of soap surround the dirt particle at the centre of the cluster and form a spherical structure called micelle.
¤ These micelles remain suspended in water like particles in a colloidal solution.
¤ The various micelles present in water do not come together to form a precipitate as each micelle repels the other because of the ion-ion repulsion.
¤ Thus, the dust particles remain trapped in micelles and are easily rinsed away with water.
¤ Hence, soap micelles remove dirt by dissolving in water.

23. Distinguish between esterification and saponification reactions of organic compounds.      (4 Marks)
A:

Esterifiation reactoin	Saponification reaction
The formation of ester is known as esterifcation reaction.	The formation of soap is known as saponification reaction.
2. Alcohol reacts with carboxylic acids to produce esters.	Higher fatty acids react with bases to form soaps.
Water is a by product in easterification reaction. e.g.: Ethyl acetate CH3COOC2H5	Glycerol is the by product in saponification reaction. e.g.: Sodium Sterate C17H35COONa

The esterification reaction is slow and reversible.	The saponification reaction is fast and irreversible.
This is an example for dehydration reaction.	This is an example for hydrolysis.
This is used to form different types of esters.	This is used to prepare soaps from long chain esters or glycerol.

24. Explain the structure of graphite in terms of bonding and give one property based on this structure.     (4 Marks)
A: ¤ Graphite forms a two dimensional layer structure with C - C bonds within the layers.
¤ There are relatively weak interactions between the layers.
        

¤ In the layer structure, the carbon atoms are in a trigonal planar environment.
This is consistent with each carbon atom in sp² hybridisation. Interactions between the sp² orbitals (overlaps) lead to the formation of C - C bonds. Each carbon atom is with one unhybridised 'p' orbital. The unhybridised 'p' orbitals interact to form a π system which is delocalised over the whole layer. The interactions known as London dispersion forces between the layers which are separated by a distance of 3.35 Aº.
Properties:
¤ Graphite has very very high melting point.
¤ Graphite is a very good conductor of electricity .
¤ Graphite is used as a lubricant and as the 'lead' in pencils.

25. Name the acid present in Vinegar.        (1 Mark)
A: Acetic acid (CH₃COOH) is present in Vinegar.
 

II. Asking Questions and Making Hypothesis
26. What happens when a small piece of Sodium is dropped into Ehtnol?    (2 Marks)
A: When a small piece of Sodium is dropped into Ethanol bubbles or effervescence of Hydrogen gas are produced.
      2 C₂H₅OH   +   2 Na        →     2 C₂H₅ONa       +     H₂ ↑
         Ethanol         Sodium              Sodium ethoxide        Hydrogen

27. Two carbon compounds A and B have molecular formula C₃H₈ and C₃H₆ respectively. Which one of the two is most likely to show addition? Justify your answer.   (4 Marks)
A: ¤ The molecular formula of A is C₃H₈.
         The molecular formula of B is C₃H₆.
¤ Compound A, C₃H₈ (Propane) is alkene. As it contains all single bonds between carbon atoms, this compound is likely to participate in substitution reaction.
¤ Compound B, C₃H₆ (Propene) is an alkene. As it contains double bond (=) between carbon atoms, it participates in addition reaction.
¤ So the compound B is most likely to show addition.
 

III. Experimentation and Field Investigation 

28. Suggest a test to find the hardness of water and explain the procedure.   (2 Marks)
A: ¤ Take two test tubes A and B.
¤ Take 20 ml of drinking water in test tube A and 20 ml of sea water in test tube B.
¤ Add 1 gm of soap in the water in each test tube.
¤ Shake the two test tubes well and observe the level of foams formed in the two tubes.
¤ We observe that the height of foam in test tube A is more than that in test tube B.
¤ It means hard water can not form leather with soap as formed by soft water.
¤ This concludes that sea water is hard water as it can not form foam with soap.

29. Suggest a chemical test to distinguish between ethanol and ehtanoic acid and explain the procedure.    (2 Marks)
Test: 1 
A: ¤ When litmus paper is dipped in ethanol, no change is observed.
¤ When blue litmus solution is poured in ethanoic acid, the solution turns red.
 

Test: 2
¤ Ethanol do not react with Sodium hydroxide.
¤ Ethanoic acid reacts with Sodium hydroxide to form Sodium acetate.
30. An organic compound 'X' with molecular formula C₂H₆O undergoes oxidation with alkaline KMnO₄ and forms the compound Y, that has molecular formula C₂H₄O₂.
a) Identify X and Y
b) Write your observation regarding the product when the compound 'X' is made to react with compound 'Y' which is used as a preservative for pickles.    (4 Marks)
A: a) ¤ C₂H₆O - Compound X is Ethanol (C₂H₅OH)
¤ C₂H₄O - Compound Y is Ethanoic acid (CH₃COOH)
b) When X (C₂H₅OH) is made to react with Y(CH₃COOH), the product is used as a preservative for pickles (Ethyl acetate is the preservative)
   C₂H₅OH  +  CH₃COOH      →  CH₃COOC₂H₅ + H₂
     Ethanol     Ehtanoic Acid                Ethyl acetate
 

IV: Information Skills and Projects
31. Prepare models of Methane, Ethane and Ethyne molecules using clay balls and match sticks.      (2 Marks)

32. Collect information about artificial ripening of fruits by Ethylene.     (2 Marks)
A: Chemistry of ripening:
¤ During the process of ripening, the starch in the fruit breaks down to form sugar. At this time the colour of the fruit skin also changes.
¤ In nature fruits ripen in certain seasons. The plants can detect the time of the season and produce ethylene (C₂H₄) and spreads across the plants.
¤ When this Ethylene reaches the fruit, it sends signals to all cells in the fruit to make enzymes which break starch into sugar.
The cells in the skin start making pigments, which give the fruit its colour.
Artificial ripening:
¤ In fact this natural ripening of fruits is a slow process. To quicken the process of ripening artificial methods are employed.
¤ Raw fruits are kept in hay-lined wooden boxes called crates. These crates are staked on shelves and a wooden fire is lit below them.
¤ The smoke from the fuel contains ethylene and acetylene gases, which induce ripening.
¤ In other method fruits are kept in a room into which acetylene or ethylene gas is sent.
¤ Some people apply Calcium Carbide (CaC₂) over fruits. This Calcium Carbide reacts with the moisture and forms acetylene, which induce ripening.
 

V: Communication Through Drawing, Model Making

33. Draw the electronic dot structure of Ethane molecule (C₂H₆).      (2 Marks)

             Electronic dot structure of Ethane (C₂H₂) molecule.
 

VI: Appreciation and Aesthetic Sense, Values

34. How do you appreciate the role of Esters in every day life?       (4 Marks)
A: Role of Esters in every day life:
¤ Esters are generally voltaille liquids with sweet or pleasant smell or fruity smell.
¤ Artificial perfumes are made with the Esters.
¤ Esters are used as flavouring agents.
¤ Esters are used in making artificial flavours and essences used in ice-creams, sweets, cool drinks etc.
¤ Saponification (soap making) is the alkaline hydrolysis of Esters.
¤ Esters are used as solvents and in plastic industry.
¤ Esters are used in air freshners.
 

VII: Application to Daily Life, Concern to Bio Diversity

35. How do you condem the use of alcohol as a social practice?
A: Evil effects of alcohol:
¤ Consumption of alcohol in the form of beverages is harmful to health.
¤ It causes severe damage to blood circulation system and nervous system.
¤ Addiction to alcohol drinking leads to heart diseases and damages the liver.
¤ It also causes ulcers in the small intestine due to increased acidity and damages the digest system.
 

36. An organic compound with molecular formula C₂H₄O₂ produces brisk effervescence on addition of Sodium carbonate/ bicarbonate. Answer the following.      (4 Marks)
a) Identify the organic compound.
b) Write the chemical equation for the above reaction.
c) Name the gas evolved.
d) How will you test the gas evolved?
e) List two important uses of the above compound?
A: a) Molecular formula of the organic compound is C₂H₄O₂. This is ethanoic acid (CH₃COOH).
b) Chemical equation:
¤ 2 CH₃COOH + Na₂CO₃ → 2 CH₃COONa + H₂O + CO₂
¤ CH₃COOH + NaHCO₃ → CH₃COONa + H₂O + CO₂
c) The gas evolved is Carbon dioxide (CO₂).
d) When the evolved gas is passed into the lime water, it turns milky.
e) Uses of ethanoic acid(CH₃COOH):
¤ Used as a preservative for pickles.
¤ Used in the preparation of drugs, dyes etc.
¤ Used as a solvent in industry.
¤ Used as a good cleaning agent.

37. 1 ml glacial acetic acid and 1 ml of ethanol are mixed together in a test tube. Few drops of concentrated sulphuric acid is added in the mixture are warmed in a water bath for 5 min.
Answer the following:
a) Name the resultant compound formed.
b) Represent the above change by a chemical equation
c) What terms is given to such a reaction?
d) What are the special characteristics of the compound formed?         (4 Marks)
A: a) The resultant compound formed is ethyl acetate (CH₃COOC₂H₅) which is an ester.
b) Chemical equation:
  CH₃COOH    +   C₂H₅OH  CH₃COOC₂H₅ + H₂O
Ethanoic acid        Ethanol                    Ethyl acetate 

c) This reaction is called esterification reaction.
d) The compound formed when poured in water, we get a sweet fruit odour.
 

Think and Discuss 
1. Why we are advised not to use animal fats for cooking?      (2 Marks)
A: ¤ If animal fat is used it is likely to cause heart disease as well as obesity.
¤ Animal fat in excess will be stored in lipocytes. As a result lipocytes expand in size till the fat in it is used as fuel.

2. Which oil is recommended for cooking? Why?       (2 Marks)
A: ¤ Canola oil is obtained from the crushed seeds of the Canola plant.
¤ Canola oil is now considered to best for cooking.
¤ Canola oil of all the oils has the lowest saturated fat content.
¤ Canola oil is rich in monosaturated fats and has high omega - 3 and omega fats.
¤ At present Canola oil is recommended for a healthy use as cooking oil.
 

Questions and Answers given in the Lesson
¤ Electronic configuration of Carbon (excited state):
1. Can carbon get Helium configuration by losing four electrons from the outershell?     (2 Marks)
A: If Carbon loses four electrons from the outer shell, it has to form C⁴⁺ ions.
This requires huge amount of energy which is not available normally.
Therefore C⁴⁺ formation also is a remote possibility.
Carbon has to satisfy its tetravalency by sharing electrons with other atoms.
It has to form four covalent bonds either with its own atoms or atoms of other elements.

2. Explain the four unpaired electrons in carbon atoms through excited state.    (2 Marks)
A: Electronic configuration of Carbon (ground state):
1s² 2s² 2p² (or) 1s² 2s² 2p_x¹ 2p_y¹ 2p_z⁰
  
     1s            2s                   2p
         Carbon (ground state)

1s² 2s¹ 2p_x¹ 2p_y¹ 2p_z¹


    1s          2s                     2p
    Carbon (excited state)

3. How do Carbon atoms form bonds in so many different ways?     (2 Mark)
A: As per valence bond theory, the four unpaired electrons in a Carbon atom is main cause to form many bonds.

4. Where the energy to excite electron to come from?        (1 Mark)
A: ¤ We have to understand that free Carbon atom would not be in excited state under normal conditions.
¤ When the Carbon atom is ready to from bonds with other atoms, the energy required for excitation is taken up from bond energies, which are the liberated energies when bonds are formed between Carbon atom and other atoms.
 

5. In Methane (CH₄) molecule all four Carbon - Hydrogen bonds are identical and bond angle is 109º.28'. How can we explain this?    (2 Marks)
A: ¤ We know that in excited state, Carbon atom has three unpaired electrons in p-orbitals and one electron in s-orbital.
¤ These four valence electrons are with different energies.
¤ These orbitals combine to form four identical orbitals.
¤ Four Hydrogen atoms form four identical C - H bonds with bond angle 109º.28'.
¤ This is called hybridisation.
 

6. How these energetically unequal valence electrons form four equivalent covalent bonds in Methane molecule?       (4 Marks)
A: ¤ When bonds are formed, energy is released and the system becomes more stable.
¤ If Carbon forms four bonds rather than two, still more energy is released and so the resulting molecule becomes even more stable.
¤ The energy difference between the 2s and 2p orbitals is very small.
¤ When Carbon atom is ready to form bonds it gets a small amount of energy from bond energies and gets excited to promote an electron from the 2s to the empty 2p to give four unpaired electrons.
¤ We have got four unpaired electrons ready for bonding, but these electrons are in two different kinds of orbitals and their energies are different.
¤ We are not going to get four identical bonds unless these unpaired electrons are in four identical orbitals.
                               
            
 

7. How to explain the four orbitals of Carbon containing unpaired electrons as energetically equal?    (1 Mark)
A: With hybridisation, the four orbitals of carbon containing unpaired electrons become energetically equal.
e.g.: Methane (CH₄)

8. How do you explain the ability of C atom to form two single covalent bonds and one double bond?    (4 Marks)
A:
       
¤ In the formation of CH₂ = CH₂ each Carbon atom in its excited state undergoes sp² hybridization by intermixing one s-orbital (2s) and two p-orbitals (say 2p_x, 2p_y) and reshuffling to form three sp² orbitals.
¤ Now each Carbon atom is left with one 'p' orbitals (say p_z) unhybridised.
¤ The three sp² orbitals having one electron each get separated around the nucleus of Carbon atoms at an angle of 120º.
¤ When Carbon is ready to form bonds one sp² orbital of one carbon atom overlaps the sp² orbital of the other carbon atom to form sp² - sp² sigma (σ) bond.
¤ The remaining two sp² orbitals of each carbon atom get overlapped by 's' orbitals of two Hydrogen atoms containing unpaired electrons.
¤ The unhybridized p_z orbitals on the two Carbon atoms overlap laterally.
                                           

9. How do you explain the ability of Carbon atom to form one single bond and one triple bond?        (4 Marks)
A: In acetylene molecule there exists a triple bond between two Carbon atoms and the fourth valency of each Carbon atom is satisfaied by Hydrogen atoms. (H - C  C - H)
¤ In C₂H₂ molecule there are two Carbon atoms and two Hydrogen atoms.
¤ In excited state each Carbon atom undergoes s-p hybridisation by mixing its one 's' orbital (2s) and one 'p' orbital (2p_x) and reshuffling to form two identical orbitals known as sp-orbitals.
¤ Each carbon atom has two unhybridised p-orbitals say (2p_y, 2p_z).
          
¤ One sp-orbital of Carbon overlaps the sp-orbital of other Carbon to give sp-sp sigma bond.
¤ The other sp-orbital of each Carbon atom overlaps 's' orbital of a Hydrogen atom to form a s-sp sigma bond.
¤ The unhybridised 'p' orbitals of one Carbon atom laterally overlap the unhybridised 'p' orbitals of other Carbon atom to give two π bonds between two Carbon atoms.
¤ Thus ethyne molecule H - C  C - H and there exists three σ-bonds and two π-bonds in the molecule.
          

10. What are bond angles H  H in CH₄, C₂H₄ and C₂H₂ molecules?     (2 Marks)
A: ¤ Bond angles H  H in CH₄ is 109.5º
¤ Bond angles H 

 H in C₂H₄ is 120º
¤ Bond angles H  H in C₂H₂ is 180º

11. How do you understand the markings (writings) of a pencil on paper?      (2 Marks)
A: ¤ When we write with a pencil, the inter layer attractions breakdown and leave graphite layers on the paper.
¤ Pencil marks are easy to remove from paper with an eraser because, the layers do not bind strongly to the paper.

12. Allotting completely one special branch in chemistry to compounds of only one element. Is it justified when there are so many elements and their compounds but not with any special branches?    (2 Marks)
A: ¤ We understand that all molecules that make life possible - carbohydrates, proteins, nucleic acids, lipids, hormones, and vitamins contain Carbon.
¤ The chemical reactions that take place in living systems are of Carbon compounds.
¤ Food that we get from nature, various medicines, cotton, silk and fuels like natural gas and petroleum almost all of them are Carbon compounds.
¤ Synthetic fabrics, plastics, synthetic rubber are also compounds of Carbon.
¤ Hence, Carbon is a special element with the largest number of compounds.

13. What are hydrocarbons?     (1 Mark)
A: The compounds containing only, Carbon and Hydrogen in their molecules are called 'hydrocarbons'.
 

14. Do all the hydrocarbon compounds have equal number of C and H atoms?         (1 Mark)
A: All the hydrocarbon compounds do not have equal number of C and H atoms.

15. Can carbon form bonds with the atoms of other elements?      (1 Mark)
A: Carbon forms compounds not only with atoms of Hydrogen but also with atoms of other elements like Oxygen, Nitrogen, Sulphur, Phosphorous, Halogens etc.
 

16. Observe the following two structures.
a) CH₃ - CH₂ - CH₂ - CH₃ b) CH₃ - CH - CH₃ 
                                                            
                                                           CH₃
1) How about their structures? Are they same?
2) How many Carbon and Hydrogen atoms are there in (a) and (b) structures?
3) Write the condensed molecular formulae for (a) and (b).
4) Do they have the same molecular formula?           (2 Marks)
A: 1) No, they are not the same compounds.
2) Carbon - 4, Hydrogen - 10
3) C₄H₁₀
4) Yes, they have the same molecular formulae.

17. Can we write the structure of a compound if the name of the compound is given?       (4 Marks)
A: Yes, we can write the structures from the name of the compound as follows:
¤ From the word root in the name write the carbon atoms in the main chain.
¤ Select counting of carbon atoms in the appropriate manner from left to right or right to left as for the name given.
¤ Attach the substituent at respective numbers of Carbon atoms as per their numbers and numerical designations.
¤ Write the functional groups formulae as per the name at the respective Carbon atom.
¤ keeping in view that the tetravalency of each Carbon atom has to be satisfied use Hydrogen atoms in the required number.
Examples:
1) 2-methyl pentan-3-ol
2) 2-bromo-3-ethyl penta-1, 4-diene
3) 3-bromo-2-chloro-5-oxohexanoic acid
4) 3-amino-2-bromo hexan-1-ol
5) 3, 4-dichloro but-1-ene

                                                                                 CH₃    OH 
                                                                                        
                                                                     1         2        3         4          5
Solution: 1) CH₃ - CH₂ - CH₂ - CH₂ - CH₃; CH₃ - CH₂ -  CH₂ - CH₂ - CH₃
                                         H
                                         
                 2) H₂C = C  -  C  -  C  =  CH₂ 
                                           
                                Br   CH₂  H 
                                         
                                       CH₃

18. Why do sometimes cooking vessels get blackened on a gas or kerosene stove?    (2 Marks)
A: ¤ Because of the inlets of air getting closed, the fuel gases do not completely undergo combustion.
¤ Hence, it forms a sooty carbon form which gets coated over the vessels.
¤ A combustion reaction is generally defined as any reaction that sustains a flame.
¤ It usually involves burning with Oxygen, though some exceptions are there, combustion reaction is always exothermic, that is energy is liberated during combustion reaction.

19. Do you know what is a catalyst?     (1 Mark)
A: Acatalyst is a substance which regulates (increase/ decrease) the rate of a given reaction without itself finally undergoing any chemical change.

20. Do you know how the police detect whether suspected drivers have consumed alcohol or not?       (4 marks)
A: ¤ The police officer asks the suspect to blow air into a plastic bag through a mouth piece of the detecting instrument which contains crystals of potassium-dichromate (K₂Cr₂O₇).
¤ As K₂Cr₂O₇ is a good oxidizing agent, it oxidizes any ethanol in the driver's breath to ethanal and ethanoic acid.
¤ Orange Cr₂O₇^2- changes to bluish green Cr³⁺ during the process of the oxidation of alcohol.
¤ The length of the tube that turned into green is the measure of the quantity of alcohol that had been drunk.
¤ Now a days police are using even an electronic instrument containing small fuel cell that measures the electrical signal produced when ethanol in the breath is oxidized.
¤ The police even use the IR spectra to detect the bonds C - OH and C - H of CH₃ - CH₂OH.

21. What pK_a?         (2 Marks)
A: ¤ pK_a is the negative value of logarithm of dissociation constant of an acid.
¤ pK_a is a measure of how much an acid dissociates in a solution.
¤ pK_a = - log₁₀K_a
¤ The lower pK_a value, the stronger is the acid.

22. What are esters?        (2 Marks)
A: Esters contains the functional group 
and the general formula is R - COO - R'. R and R' are alkyl groups or phenyl groups.

23. What is a true solution? And colloidal solution?              (2 Marks)
A: ¤ A true solution is that in which the solute particles dispersed in the solvent are less than 1 nm in diameter.
¤ A colloidal solution contains the solute known as 'dispersed phase' with its particles with diameters greater than 1 nm but lesser than 1000 nm in the solvent known as dispersion medium.
 

24. What is the action of the soap particles on the greasy cloth?     (4 Marks)
A: ¤ Soaps and detergents make oil and dirt present on the cloth come out into water, there by making the cloth clean.
¤ Soap has one polar end and one non-polar end.
¤ The polar end is hydrophilic in nature and this end is attracted towards water.
¤ The non-polar end is hydrophobic, in nature and it is attracted towards grease or oil on the cloth, but not attracted towards water.
¤ When soap is dissolved in water, its hydrophobic end attach themselves to dirt and remove it from the cloth.
¤ The hydrophobic ends of the soap molecules move towards the dirt or grease particles.
¤ The hydrophobic ends attached to the dirt particle and try to pull out.
¤ The molecules of soap surround the dirt particle at the centre of the cluster and form a spherical structure called micelle.
¤ These micelles remain suspended in water like particles in a colloidal solution.
¤ The various micelles present in water do not come together to form a precipitate as each micelle repels the other because of the ion-ion repulsion.
¤ Thus, the dust particles remain trapped in micelles and are easily rinsed away with water.
¤ Hence, soap micelles remove dirt by dissolving in water.
 

ACTIVITIES

Activity: 1
1. Observe the names of the following compounds. Give reasons in the space provided.
Divide the given name as per the notations given above and identify the parts in the name through the numbers given above from (1) to (11) and write them in your note book. (Any 4 items: 4 Marks)
(1) = Number (2) = Numerical prefixes (3) = Secondary prefix
(4) = Primary prefix (5) = Word root (6) = Numbers
(7) = Numerical prefixes (8) = Primary suffix (9) = Numbers
(10) = Numerical prefixes (11) = Secondary suffixes.
One example is given to guide you in dividing the name as per notation:
a) CH₃ - CH₂ - CH₂ - CH₃ : Butane .................

      4        3         2        1
b) CH₃ - CH₂ - CH = CH₂ : But - I - ene .................

     1         2       3         4
c) CH₃ - CH - CH₂ - CH₃ : 2 – Chloro butane .................
                
               Cl

     1          2       3       4
d) CH₃ - CH - CH - CH₃: 2, 3 - Dichloro butane .................
            
     Cl       Cl

   4         3        2       1
e) CH₃ - CH = CH = CH₂ : Buta 1, 2 – diene .................

    4         3         2         1
f) CH₃ - CH₂ - CH₂ - CH₂ - OH : Butan - 1 - ol .................

     4         3         2         1
g) CH₃ - CH₂ - CH₂ - CHO : Butanal .................

h) CH₃ - CH₂ - CH₂- COOH : Butanoic acid .................

i) CH₂ - CH₂ : Cyclo butane .................
            
   CH₂ - CH₂

j) Br     Br : 1, 2 dibromo cyclo butane .................
        
   CH - CH
       
   CH₂-CH₂

k) CH₂ - CH - CHO : 2, 3 dichloropropanal .................
      

       
      Cl       Cl

l) CH₃ - C - CH₂ - CH₂ - CH₃ : Penta n – 2 – one .................
              
              O

 

Activity: 2
¤ Take 1 ml of ethanol (absolute alcohol) and 1 ml of glacial acetic acid along with a few drops of concentrated sulphuric acid in a test tube.
2. Do the following activity and answer the questions given.      (4 Marks)
A:
                            

¤ Warm it in a water-bath or a beaker containg water for at least five minutes as shown in fig.
¤ Pour the warm contents into a beaker containing 20-50 ml of water and observe the odour of the resulting mixture.
1) What do you notice?
A: We notice a sweet odour substance formed.
2) By what name is this reactioned called?
A: This reaction is called esterification reaction.
3) Under what condition does this reaction take place?
A: The reaction takes place only in the acid medium.
4) Why is water bath used?
A: The substances present in the test tube are highly inflammable. So water bath is used. Direct heating is not desirable.
5) What is the name of the product formed in this activity?
A: An ester (RCOOR) is the product formed in this activity.
 

Activity: 3 

3. Describe the activity of formation of micelle? Explain the cleansing action of soap. (4 Marks)
A:
              
¤ Take about 10 ml of water each in two test tubes.
¤ Add a drop of oil (cooking oil) to both the test tubes and label them as A and B.
¤ Add a few drops of soap solution to test tube B.
¤ Now shake both the test tubes vigorously for the same period of time.
¤ We cannot observe that the oil and water layers separately in both the test tubes after shaking is stopped
¤ If the test tubes are left for some time undisturbed the separation of oil layer is observed in test tube B as it contains soap solution.
¤ This is the basic idea in employing soap as a cleansing agent.
Cleansing action of soap
¤ Suppose that we put dirty cloth in the soap solution. Dirt is mainly greasy matter.
¤ The soap molecules are arranged radially with hydrocarbon ends directed inwards into the greasy matter and ionic part directed outwards into water.
¤ When a dirty cloth is inserted in the solution then the hydrocarbon part sticks to the dirt or oil.
¤ With a little agitation the dirt particle get entrapped by the soap micelles and get dispersed in water due to which the soap water gets dirty and the cloth gets cleaned. 
 

ADDITIONAL QUESTIONS AND ANSWERS
I. Conceptual Understanding

1. Write the different possibility of bonds formation by a Carbon atom.                 (4 Marks)
A: The possibility of bonds formation by a Carbon atom is as:
A) i) Four single covalent bonds, with atoms of same element like Hydrogen, Chlorine.

ii) Four single covalent bonds, with atoms of different elements
    

B) Carbon atoms may form one double bond and two single bonds.

C) Carbon atom may form one single bond and a triple bond.
e.g.: H - C C - H or CH₃ - C N or Carbon atoms may also form two double bonds as in CH₂ = C = C H₂

2. Write a note on 'sp³' by hybridisation.   (4 Marks)
A: ¤ In the excited Carbon atom its one s-orbital (2s) and three p-orbitals (2p_x, 2p_y, 2p_z), intermix and reshuffle into four identical orbitals known as sp³ orbitals.
¤ Thus, Carbon atom undergoes sp³ hybridisation.
¤ The four electrons enter into the new four identical hybrid oribitals known as sp³ hybrid orbitals one each as per Hund's rule. (because they are made from one 's-orbital and three 'p-orbitals' they are called sp³ orbials.)
      

¤ The hybridisation enables the Carbon to have four identical sp³ hybrid orbitals and these have one electron each.
¤ Since Carbon has four unpaired electrons, it is capable of forming bonds with four other atoms may be Carbon or atoms of some other monovalent element.
¤ When Carbon reacts with Hydrogen, four Hydrogen atoms allow their 's' orbitals containing one electron each to overlap the four sp³ orbitals or Carbon atom which are oriented at an angle of 109º28'. (Four orbitals of an atom in the outer shell orient along the four corners of a tetrahedron to have minimum repulsion between their electrons.)
¤ The nucleus of the atom is at the centre of the tetrahedron. See figures below:
        
¤ This leads to form four sp³ - s sigma bonds between Carbon atom and four Hydrogen atoms. All these bonds are of equal energy.

3. What is allotropy? Describe the allotropes of Carbon.         (4 Marks)
A: Allotropy: The property of an element to exist in two or more physical forms having more or less similar chemical properties but different physical properties is called allotropy.
Allotropes: The different forms of the element are called allotropes. Allotropes form due to the difference in the arrangement of atoms in the molecules.
The allotropes of Carbon are classified into two types. They are
¤ Amorphous forms
¤ Crystalline forms
Amorphous forms
Different amorphous allotropes of Carbon are Coal; Coke; Wood Charcoal; Animal Charcoal; Lamp black, Gas carbon; Petroleum coke; Sugar charcoal.
Crystalline forms
¤ Carbon atoms can arrange themselves into different hybridised chemical bonds.

¤ Therefore they exhibit different physical and chemical structures such as diamond and graphite.
¤ Carbon is solid phase can exist in three crystalline allotropic forms: diamond, graphite and buckminster fullerene.
¤ Diamond and graphite form covalent network structures whereas Buckminster fullerene has a molecular solid structure with discrete ₆₀C molecules.
¤ As these crystalline allotropes differ in their structures, they possess different physical properties.
¤ Nano tubes are another allotropic form of Carbon discovered in 1991 by Sumio li Jima.

4. Describe the structure of Buckminster fullerene (₆₀C).
A: Buckminster fullerene (₆₀C)
¤ Buckminster fullerenes are molecules of varying sizes that are composed entirely of Carbon.
¤ The arrangement of these molecules leads to the form of a hallow sphere, ellipsoid, or tube depending upon their orientations. Fullerenes are formed when vaporized Carbon condenses in an atmosphere of an inert gas.
¤ Bucky balls: Spherical fullerenes are also called bucky balls.
¤ Buckminster fullerene (₆₀C) contains nearly spherical ₆₀C molecules with the shape of a soccer ball.
              

¤ Fullerene, ₆₀C molecule contains 12 pentagonal and 20 hexagonal faces on its soccer ball shape, and each Carbon atom has sp² hybridized orbitals.
¤ Fullerenes are under study for potential medicinal use - such as specific antibiotics to target resistant bacteria and even target certain cancer cells such as melanoma.
 

5. What are nano tubes? Describe their structure. Why are they so called?  How are these useful?   (4 Marks)
A: Nano tubes:
¤ Nano tubes are another allotropic form of Carbon discovered in 1991 by Sumio li Jima.
Structure:
¤ Nano tubes consist of hexagonal arrays of covalently bonded Carbon atoms, similar to the sheets in graphite. Unlike the flat graphite sheets, in nano tubes the sheets are rolled into cylinders. Due to this reason they are called nano tubes.
Usefulness:
¤ Nano tubes like graphite, are electrical conductors and can be used as molecular wires. In integrated circuits nano tubes are used instead of copper to connect the components together. Scientists inserted biomolecules into nano tubes to inject them into a single cell.

6. Describe the versatile nature of Carbon? Why is organic chemistry totally allotted to Carbon compounds?    (4 Marks)
A: Versatile nature of Carbon:
¤ By the eighteenth century scientists tried to explain the difference between the compounds in a broader way.
¤ J.J.Berzelius (1807) named the compounds that derived from living organism as organic compounds and those from non-living materials as inorganic compounds.
¤ He thought that organic compounds would be prepared in the living bodies through vital force, the essence of life.
¤ As this force is absent outside the living bodies, it was thought that the so called organic compounds could not be synthesized in the laboratories.
¤ Surprisingly F.Wohler (1828) produced an organic compound Urea in the laboratory by heating an inorganic salt Ammonium Cyanate.
     

Organic Chemistry - Carbon compounds
¤ It inspired many other chemists and they were successful to prepare the so called organic compounds Methane, Acetic acid etc., in the laboratory.
¤ This gave a death blow to the idea that organic compounds are derived from living organism.
¤ Chemists thought about a new definition for organic compounds.
¤ After observing the structures and elements of organic compounds, they defined organic compounds as compounds of Carbon.
¤ Therefore, organic chemistry is totally allotted to Carbon compounds.

7. What is catenation property?        (2 Marks)
A: Catenation
¤ Another peculiar behaviour of Carbon is its ability to form longest chains with its own atoms.
¤ If any element forms bonds between its own atoms to give big molecules we call that property as catenation property.
¤ Carbon has the ability to form longest chains containing millions of Carbon atoms in molecules like some proteins.
¤ Sulphur, Phosphorus and some other non metals have this property but to a very less extent.
 

8. Describe the ability of Carbon to form bonds in so many ways.        (2 Marks)
A: Carbon can form:

b) A double bond and two single covalent bonds (  C = C)
c) A single covalent bond and a triple bond (-C  C), or two double bonds
(C = C = C) with its own atoms or atoms of other elements - to satisfy its tetravalency.

9. What are hydrocarbons? How are they classified? Explain.          (2 Marks)
A: ¤ The compounds containing only Carbon and Hydrogen in their molecules are called hydrocarbons.
¤ Hydrocarbons are classified into two categories known as open chain hydrocarbons and closed chain hydrocarbons. Open chain hydrocarbons are also called aliphatic hydrocarbons or acyclic hydrocarbons.

Open and closed chain hydrocarbons
¤ Let us observe the following structural formulae of different hydrocarbons.
1) CH₃ - CH₂ - CH₂ - CH₂ - CH₃ n - pentane, a straight chain compound
2) CH₃ - CH - CH₂ - CH₃, Iso pentane, a branched chain compound
                 
                CH₃
3) CH₂ - CH₂ cyclo pentane, a cyclic compound or a ring compound
             
     CH₂    CH₂
            
          CH₂

10. Define Alkanes, Alkenes and Alkynes.      (2 Marks)
A: All hydrocarbons (both aliphatic and cyclic hydrocarbons) are again classified as Alkanes, Alkenes and Alkynes.
¤ Hydrocarbons containing only single bonds between Carbon atoms are called Alkanes.
¤ Hydrocarbons containing atleast one double bond between Carbon atoms are called Alkenes.
¤ Hydrocarbons containing atleast one triple bond between Carbon atoms are called Alkynes.

11. Explain about saturated and unsaturated hydrocarbons?     (2 Marks)
A: Saturated and unsaturated hydrocarbons
¤ The hydrocarbons containing only C - C single bonds are known as saturated hydrocarbons.
¤ All alkanes are saturated hydrocarbons.
¤ The hydrocarbons that contain atleast one double bond (C = C) or contain atleast one triple bond (C  C) between the two Carbon atoms are called unsaturated hydrocarbons.
¤ Alkenes and Alkynes are the examples for unsaturated hydrocarbons.
¤ Straight chain, branched chain and closed chain hydro Carbon compounds may be saturated or unsaturated.

12. Give few examples of halo hydrocarbons.        (1 Mark)
A: CH₃Cl, CH₃ - CH₂ - Br, CH₂Cl - CH₂I, CH₃ - CHCl₂ are some examples of halo hydrocarbons. These are halogen derivatives of hydrocarbons.
 

13. How do we get alcohols? What are they? Give some examples.         (2 Marks)
A: ¤ If a hydrogen atom of H₂O molecule is replaced by 'R', we get alcohols R - OH.
¤ The hydrocarbons that contain -OH group are called alcohols.
¤ CH₃OH, CH₃CH₂OH, CH₃ - CHOH - CH₃ etc are some examples of alcohols.

14. What are aldehydes. Mention few examples.
A: The hydro carbons with functional group - CHO are called aldehydes.
     
(Formaldehyde)      (Acetaldehyde)        (Propionaldehyde)
are few examples of aldehydes
¤ The general formula of aldehydes is R - CHO, Where R = alkyl group of
Hyderogen and - CHO is functional group.
 

15. What are Ketones? Write an example of a ketone. What do you understand by the term ketone group?   (2 Marks)
A: ¤ The hydrocarbons with  = O functional group are called ketones.
             O                                          O
                                                      

¤ CH₃ - C - CH₃,         CH₃ - CH₂ - C - CH₃  are examples of Ketones.
    (Dimethyl Ketone)   (Ethyl methyl ketone) 
¤  = O group is known as ketone group.
¤ General formula of ketone is 
Where R, and R' are alkyl groups which may be same or different.

16. What is the general formula of Carboxylic acids. Write few carboxylic acids with their molecular formula. How do you identify carboxylic group?        (2 Marks)
A: ¤ The general molecular formula of carboxylic acid is R - COOH, Where
R is an alkyl group of H atom.
¤ H - C = O,     CH₃ - C = O,     CH₃ - CH₂ - C = O
                                                                  
       OH                      OH                               OH
     Formic acid      Acetic acid       Propionic acid
¤ - C = O group is called the carboxyl group.
     
    OH

17. What are ethers? Write some ethers with their structural formula.      (2 Marks)
A: ¤ Ethers are Carbon compounds related to H₂O in such a way that both Hydrogen atoms are replaced by two alkyl groups which may be same or different.
e.g.: CH₃ - O - CH₃,    CH₃ - CH₂ - O - CH₃,     CH₂ = CH - O - CH₃ etc.
          Di methyl ether    Ethyl methyl ether         Methyl vinyl ether
 

18. How are esters obtained? Give the structural formula of some esters.     (2 Marks)
A: ¤ These compounds are derivatives of carboxylic acids. If the Hydrogen atom of -COOH gets replaced by 'R', the alkyl group esters are obtained.
             O                                     O                                     O
            

                                                                          
¤ CH₃ -C - OCH₃,  CH₃ - CH₂ - C - OCH₃,  CH₃ - CH₂ - C -OCH₂CH₃ etc.
     Di methyl ester       Ethyl methyl ester              Di ethyl ester

19. What is an amine group? How do we get amines?            (4 Marks)
A: Amines.                                                                                   NH₂
                                                                                                      
e.g.: CH₃ - NH₂, CH₃ - CH - NH₂, CH₃CH₂NH₂, CH₃ - CH₂ - C - CH₃
                                                                                                   
                                        CH₃                                                      CH₃
¤ - NH₂ group is called amine group. We may compare amines to NH₃ as we have done ROH and R - O - R' to H₂O.
¤ If one hydrogen atom is replaced from NH₃ by an alkyl group we get the so called primary amines.
¤ If two hydrogen atoms of NH₃ are replaced by two alkyl groups (same or different). We get secondary amines and if all the three Hydrogen atoms are replaced by the same or different alkyl groups we get tertiary amines.

20. What is the importance of functional groups in Carbon compounds?       (2 Marks)
A: ¤ The characteristic properties of an organic compound depend mainly on an atom or group of atoms in its molecule known as the functional group.
¤ Organic compounds are classified by the type of functional group they contain.
¤ Functional groups are responsible for the behaviour of the organic compounds.
¤ Compounds containing the same functional group undergo similar types of reactions.
 

21. Explain briefly about 'isomerism' and 'isomers' with suitable examples.       (4 Marks)
A: ¤ If we look at the following structures.
a) CH₃ - CH₂ - CH₂ - CH₃      b) CH₃ - CH - CH₃
                                                                      
                                                                     CH₃
We understand
a) The first one is called butane (or) in the common system it is known as n-butane.
b) The second one is called 2-methyl propane or iso-butane in the common system.
¤ We find both of these compounds in nature. They have different properties due to the difference in their structures.
¤ Compounds of this type which have the same molecular formula but different properties are called isomers.
¤ The phenomenon of possessing same molecular formula but different properties by the compounds is known as isomerism.
¤ The compounds that exhibit isomerism are called isomers.
     (iso = same; meros = part, i.e., they have same molecular formula)
¤ In the above example isomerism is due to the difference in the structures. Therefore, it is called the structural isomerism.
 

22. Explain the term 'Homologous Series'.       (2 Marks)
A: ¤ The series of Carbon compounds in which two successive compounds differ by - CH₂ unit is called homologous series.
e.g.:  CH₄,  C₂H₆,  C₃H₈, ......
          CH₃OH, C₂H₅OH, C₃H₇OH, ......
¤ If we observe above series of compounds, we notice that each compound in the series differs by -CH₂ unit by its successive compound.
 

23. Write the characteristic features of Homologous series of organic compounds.  (4 Marks)
A: Homologous series of organic compounds have following characteristic features.
¤ They have one general formula.
e.g.: Alkanes (C_nH_2n+2); alkynes (C_nH_2n-2); alcohols (C_nH_2n+1) OH etc.
¤ Successive compounds in the series possess a difference of (-CH₂) unit.
¤ The possess similar chemical properties due to the same functional group
e.g.: alcohols, aldehydes and carboxylic acids have functional groups
         C - OH, C - CHO and C - COOH respectively.
¤ They show a regular gradation in their physical properties.
For example: we may take alkanes, alkenes, alkynes, alcohols, aldehydes, and carboxylic acids etc. as homologous series. The individual members of a homologous series are called homologs.

24. What is the need for establishing 'nomenclature of organic compounds'?     (2 Marks)
A: Nomenclature of organic compounds
¤ We have millions of organic compounds. As number of organic compound is very big. It is difficult to remember their names individually.
¤ To overcome this problem they have to be properly named.
¤ For this, the International Union of Pure and Applied Chemistry (IUPAC) had been formed, and one of its responsibilities is to name the organic and inorganic compounds in a systematic order.

¤ The basic idea behind the systematic nomenclature is that there should be only one name for the given structure throughout the world and also there should be only one structure for the given name.

25. Explain how does the IUPAC name of an organic compound give the information about the compound.   (2 Marks)
A: The IUPAC name of an organic compound gives information about:
a) The number of carbon atoms present in the molecules. We call this part of the name as word root.
C₁ - meth; C₂ - eth; C₃ - prop; C₄ - but; C₅ - pent; C₆ - hex;
C₇ - hept; C₈ - oct; C₉ - non; C₁₀ - dec and so on.
b) The substituents in the molecule; which are shown as the prefix.
c) The functional group in the molecule; which is shown as the suffix.
 

26. What does the terms 'prefix', 'suffix' tell about the organic compound?     (4 Marks)
A: Prefix: Prefix again has several parts known as primary prefix, secondary prefix, numerical prefix and number prefix etc.
¤ Primary prefix is 'cyclo' and it is useful only for cyclic compounds which have properties similar to aliphatic compounds. If the compounds are not cyclic, this part of the name is absent.
¤ Secondary prefix tells about the second grade functional groups known as substituents. They are 'halogens' which are written as halo, alkyl groups (R), alkoxy groups (-OR) etc which are written as alkyl, alkoxy.
Suffix: It also contains several parts known as primary suffix, secondary suffix, numerical suffix and number suffix etc.
¤ Primary suffix tells about the saturation of the compound. For saturated (C - C) it is 'an' and Carbon atoms are attached to one another only through single bonds in the compounds.
¤ For unsaturated (C = C) double bonded compounds it is 'en' and for unsaturated triple bonded (C  C) compounds it is 'yn'.
¤ There is a secondary suffix that tells about the functional groups with the particular term.
For example: For hydrocarbons it is 'e'
                         for Alcohols it is '-ol'
                         Aldehydes it is '-al'
                         Ketones it is '-one' and
                         Carboxylic acid it is '-oic acid'.

¤ Numerical prefixes like di, tri are written before the secondary prefixes, primary suffixes and secondary suffixes, when the same substituent, multiple bond or functional group is repeated twice, thrice etc as di, tri etc respectively.
¤ Numbers are written to tell about to which Carbon atoms of the compound the substituent (s), multiple bond (s) or functional group (s) are attached.

27. Write the order to be followed while naming organic compound.      (2 Marks)
A: The order is as follows:

28. What differences among (1), (2), (3); (6), (7), (8) and (9), (10) and (11) do you find?     (4 Marks)
A: ¤ (1), (2) are numbers and numerical designations to be written for secondary prefixes (3) which tell about the position and repetitions of second grade functional groups known as substituents respectively.
          1         2       3       4
e.g.: CH₃ - CH - CH - CH₃
                         
                  Cl      Cl
     
¤ (6) and (7) tell about the positions and repetitions of the multiple bonds in the structures of the molecule of the compound. These are related to the primary suffix (8) that tells about the unsaturation.
          5         4     3       2        1
e.g.:  CH₃ - C = CH - CH  CH
 

¤ (9) and (10) tell about the positions and repetitions of the functional group or principal functional group (11) in a poly functional compound. It gives the information which carbon represents it or to which carbon that functional group is attached and how many times it is repeated. If it comes only once we need not write mono i.e. if no numerical prefix is present it is understood that the functional group is not repeated.
¤ Similarly, in the names of aliphatic compounds word root primary suffix (8) and secondary suffix (11) are definitely present and all others may or may not be present.
e.g.: CH₃ - CH₂ - CH - CH₂ - OH
                              
                            OH

29. Write about the punctuation adopted in the IUPAC name of the organic compound. (2 Marks)
A: Punctuation: Numbers are separated by a comma (,) a numbers & designations by hyphen (-).
¤ If we find more than one substituent in the structure we have to follow alphabetical order while naming them. For this numerical prefixes should not be considered. Substituents: X (halo), R (alkyl), -OR (alkoxy), -NO₂ (nitro), NO (nitroso) etc.

¤ If we find more than one functional group in the structure we select the principal functional group and write it as secondary suffix. All other functional groups become substituents.
¤ A decreasing order of priority for choosing and naming a principal characteristic group. This should written as secondary suffix.
¤ - COOH >  (CH₃CO)₂ O >  -COOR >  -COX >  - CONH₂ >
        Acid        anhydride           ester a   acid halide    amide
- CN >  - CHO  > >C = O >   R - OH > - NH₂
 nitrile  aldehydes  ketones    alcohols    amines

30. How is the numbering of Carbon atoms done?       (2 Marks)
Numbering of Carbon atoms
A: ¤ We can number Carbon atoms from left to right or from right to left so that sum of the numbers indicating the positions of substituents and functional groups should be minimum possible.
¤ The functional group Carbon should be given the lowest number even if it does not obey Rule (1).
¤ The carbon atoms of the chain terminating functional group say -CHO or -COOH groups should be given always number '1' even if it does not obey Rules (1) & (2).

31. Mention some important reactions among organic compounds.       (2 Marks)
A: Some important reactions among organic compounds are
1) Combustion
2) Oxidation reactions
3) Addition reactions
4) Substitution reactions

32. Write a note on 'combustion reaction'.      (4 Marks)
A: Combustion reactions:
¤ Carbon and its compounds burn in presence of Oxygen or air to give CO₂, heat and light.
¤ The process of burning of Carbon or Carbon compound in excess of Oxygen to give heat and light is called the combustion reaction.
¤ In the reactions carbon is in its maximum oxidation state of 4⁺ in the product.

e.g.: 1) C + O₂ → CO₂ + Energy
        2) 2 C₂H₆ + 7 O₂ → 4 CO₂ + 6 H₂O + Energy
        3) CH₃CH₂OH + 3 O₂ → 2 CO₂ + 3 H₂O + Energy
¤ Generally, saturated hydrocarbons burn with a clear light blue flame, whereas, unsaturated hydrocarbons burn with yellow flame with soot (carbon).
¤ If air is not sufficiently available during combustion, even saturated hydrocarbons give sooty flame.
¤ When Coal, Petroleum etc., burn in air they give oxides of sulphur and nitrogen in addition to CO₂ and H₂O which pollute the environment.
¤ When Coal or Charcoal is burnt sometimes they just glow red without flame. This is because to get a flame gaseous fuels should burn.
¤ Most of the aromatic compounds burn with sooty flame.

33. What are oxidation reactions? Explain with an example?         (2 Marks)
A: Oxidation reactions
¤ Though combustion is generally oxidation reaction, all oxidation reactions are not combustion reactions.
¤ Oxidation reactions may be carried out using oxidizing agent.
¤ Oxidizing agents or oxidants are substances that oxidize other substances.
¤ They themselves undergo reduction.
¤ e.g.: Alkaline Potassium permanganate or acidified Potassium dichromate in solutions act as oxidizing agents and supplies Oxygen to convert alcohols into Carboxylic acids.
¤ Ethyl alcohol undergoes oxidation to form the product acetaldehyde and finally acetic acid. (See following equation)

34. Which type of organic compounds undergo addition reactions? Explain with an example. (2 Marks)
A: Addition reactions
¤ Unsaturated organic compounds that contain multiple bonds (=,  bonds) like alkenes and alkynes undergo addition reactions to become saturated.
¤ During the reactions addition of the reagent takes place at the double bonded or triple bonded Carbon atoms.


¤ In the above reactions 'Ni' acts as 'catalyst'.

35. With a suitable example explain how substitution reactions take place?       (4 Marks)
A: Substitution reaction:
¤ A reaction in which an atom or a group of atoms in a given compound is replaced by other atom or group of atoms is called a substitution reaction.
¤ Alkanes, the saturated hydrocarbons are chemically least reactive. Therefore they are also called paraffins (parum = little, affins = affinity, i.e. no affinity towards chemical changes). However they undergo some chemical changes under suitable conditions which are substitution reactions.

¤ For example, Methane (CH₄) reacts with Chlorine in the present of sunlight.
Hydrogen atoms of CH₄ are replaced by Chlorine atoms.
¤  CH₄       +      Cl₂         CH₃Cl              +        HCl
   Methane                              Methyl Chloride     Hydrogen Chloride
   CH3Cl      +     Cl₂           CH₂Cl₂          +         HCl
   Methyl Chloride                  Methylene Chloride    Hydrogen Chloride
    CH₂Cl₂    +     Cl₂           CHCl₃           +         HCl
    Methylene   chloride           Chloroform                  Hydrogen Chloride
     CHCl₃       +     Cl₂            CCl₄             +       HCl
Chloroform                                         Carbon                Hydrogen Chloride
                                                          Tetrachloride

36. Describe the preparation and properties of Ethanol.     (4 Marks)
A: Ethanol (Ethyl alcohol)
Preparation:
¤ Ethanol is prepared on large scale from Ethene by the addition of water vapour to it in the presence of catalysts like P₂O₅, Tungsten oxide at high pressure and temperature.
CH₂ = CH₂   +   H₂O    

      CH₃CH₂OH
     ethene                  100 - 300 atm   ethyl alcohol
                                        At 300 ºC
¤ Grains such as corn, wheat, barly are common sources for ethanol. Therefore, it is also called grain alcohol.
Cooking grain + Sprouted barley → Glucose  Ethanol + CO₂
       (starch)          (called Malt)                         Enzymes
¤ The process of conversion of starches and sugars to C₂H₅OH is called fermentation process.

Properties
¤ Ethanol is a colourless liquid with characteristic sweet odour.
¤ Pure ethanol boils at 78.3ºC. Pure ethanol is called absolute (100%) alcohol.
¤ Denatured alcohol is ethanol that contains impurities that make it undrinkable.
¤ The impurities are Methanol, methyl isobutyl ketone, aviation gasoline etc. It is toxic and 200 ml of it is a fatal dose to an adult.
¤ Solution of about 10% ethanol in gasoline (gasohol) is a good motor fuel.
¤ Ethanol is commonly called alcohol and is active ingredient of all alcoholic drinks.
¤ Consumption of small quantity of dilute ethanol causes drunkenness.
¤ In addition, as it is a good solvent it is also used in medicines such as tincture iodine, cough syrups and many tonics.
¤ As ethanol is similar to water molecule (H₂O) with C₂H₅ group in place of Hydrogen, it reacts with metallic sodium to liberate Hydrogen and form sodium ethoxide.
       2 C₂H₅OH + 2 Na → 2 C₂H₅ONa + H₂
          Ethanol                        Sodium ethoxide

Action of conc. H₂SO₄: Ethanol reacts with conc. H₂SO₄ at about 170ºC (443 K) to give ethene. It is a dehydration reaction. H₂SO₄ is a dehydrating agent and removes H₂O.

37. Write the properties of Ethanoic acid?     (4 Marks)
A: Ethanoic acid (Acetic acid, CH₃COOH)
¤ Ethnoic acid is a colourless liquid with characteristic unpleasant odour. It is soluble in water and more acidic than H₂O or ethanol, but less acidic than mineral acids.
¤ Ethanoic acid is commonly called as acetic acid. 5 - 8% solution of acetic acid in water is called vinegar and is used widely as a preservative in pickles.
Chemical properties
Acidity: (Reaction with metals and alkalies)
¤ Ethanoic acid reacts with active metals like Na to liberate Hydrogen.
This reaction is similar to that of ethanol.
2 CH₃COOH      +      2 Na     →    2 CH₃COONa   +   H₂
   Acetic acid        Sodium                  Sodium acetate

¤ Ethanoic acid with NaOH to form salt and water.
   CH₃COOH       +      NaOH          →    2 CH₃COONa    +   H₂O
   Acetic acid           Sodium hydroxide
¤ Ethanoic acid reacts with Sodium carbonate and Sodium hydrogen carbonate which are weaker bases and liberates CO₂
    2 CH₃COONa    +     Na₂CO₃        →    2 CH₃COONa     +    H₂O   +   CO₂
                                Sodium carbonate
CH₃COOH   +   NaHCO₃       →   CH₃COONa   +   H₂O   +   CO₂
                        sodium bi carbonate

38. How is the strength of an acid expressed. How is this useful?        (2 Marks)
A: ¤ The strength of acids may be expressed in terms of their pKa values. These values are related to their dissociation in aqueous solutions.
¤ pK_a is the negative value of logarithm of dissociation constant of an acid.
pK_a = -log₁₀ K_a

¤ The lower the value of pKa, the stronger is the acid.
¤ Note that pK_a of 1.0 M HCl is zero but pKa of CH₃COOH is 4.76. pK_a values are useful to tell about acid strength.
¤ Strong scids have pK_a < 1, acids with pKa between 1 and 5 are moderately strong and weak acids have pKa between 5 and 15.
¤ The weakest acids have pK_a > 15.
¤ Note that pKa values less than zero are not generally given as they are of no use to give in terms of pKa. They may be directly given in terms of Ka.

39. Explain 'esterification'.          (4 Marks)
A: ¤ The reaction between carboxylic acid and an alcohol in the presence of conc. H₂SO₄ to form a sweet odoured substance, ester with the functional group 

 is called esterification.
¤ The esterification reaction is slow and reversible.
¤ The equation for the reaction between an acid RCOOH and an alcohol R'OH is
(where R and R' can be the same or different) is:

¤ So, for example, if we want to prepare ethyl ethnoate or ethyl acitate from ethnoic acid and ethanol, the equation would be:

40. What is soap?         (2 Marks)
A: ¤ Soap is a sodium or potassium salt of a higher fatty acid like palmitic acid (C₁₅H₃₁COOH), stearic acid (C₁₇H₃₅COOH), oleic acid (C₁₇H₃₃COOH) etc.
¤ The formula of a soap in general is RCOONa or RCOOK, Where R = C₁₅H₃₁; C₁₇H₃₅ etc.

41. What are fats? Explain saponification reaction.         (4 Marks)
A: ¤ Fats are esters of higher fatty acids and the trihydroxy alcohol known as glycerol.
                    CH₂OH
                    
Glycerol is CHOH, propane - 1, 2, 3 -triol.
                    
                    CH₂OH
¤ When fats are treated with Sodium hydroxide, sodium salts the fatty acids and glycerol is formed. the Sodium salts of these higher fatty acids being soaps the reaction is the soap formation reaction which is generally called as 'saponification reaction'.

Saponification reaction
¤ Alkaline hydrolysis of tristers of higher fatty acids producing soaps is called saponification.
¤ Soaps are good cleansing agents.
 

II. Asking Questions And Making Hypothesis

42. Which of the following compounds are unsaturated? Justify your answer.
a. CH₃ - CH₂ - CH₃                b. CH₃ - CH = CH₂
c. CH - CH₂                             d. HC  C - CH = CH₂
           
    CH - CH₂
e. CH₃ - CH - CH = CH₂         f. CH₃ - CH₂ - CH₂ - CH₂
                                                                                 
               CH₃                                                               CH₂ - CH₃
A: a) CH₃ - CH₂ - CH₃
This is a saturated hydrocarbon as it has only single bonds.
b) CH₃ - CH = CH₂
This is an unsaturated hydrocarbon as it has a double bond.

c) CH  -  CH₂
              
    CH  -  CH₂
This is an unsaturated hydrocarbon as it has a double bond.
d) HC 

 C - CH = CH₂
As this organic compound has a triple bond and a double bond it is an unsaturated hydrocarbon
e) CH₃ - CH - CH = CH₂
              
              CH₃
This is an unsaturated hydrocarbon. It has a double bond.
f) CH₃ - CH₂ - CH₂ - CH₂
                                    
                                    CH₂ - CH₃
This is a saturated hydrocarbon. All the bonds in this organic compound are single bonds only.

43. Identify the compounds in the following, as branched chain and closed chain compounds.
a) CH₃ - CH - CH - CH₃                               b)             CH₂ - CH₂
                                                                                      
               CH₃ CH₂ - CH₃                                   H₃C - CH - CH₂
                                                                                              CH₃
                                                                                              
c) CH - CH₂                                                     d) HC  C - C - CH₃
      

                                                                                  
     CH   CH₂                                                                         CH₃
         
         CH₂
A: a) CH₃ - CH - CH - CH₃
                           
                    CH₃  CH₂ - CH₃
This is a branched chain organic compound.

This is a closed chain organic compound.
(c)  CH - CH₂
        

      
       CH    CH₂
          
           CH₂
This is a closed chain organic compound.
d)                  CH₃
                     
     HC  C -  C - CH₃
                     
                     CH₃
This is a branched chain organic compound.

44. What are associated colloids?            (2 Marks)
A: ¤ Soap is an electrolyte.
¤ When soap is put in water in very small amount it gives low concentrated solutions.
¤ It gives true solution but, above a particular concentration known as critical micelle concentration (CMC), the soap particles get aggregated and these aggregated particles are of colloidal size known as micelles or associated colloids.
 

III. EXPERIMENTATION AND FIELD INVESTIGATION

45. Study the following examples and understand how the parts in the name are identified through the numbers.       (Each one 2 Marks)
Example: CH₃ - CH₂ - OH
                  propanal - (C) of CHO included in the name of the main chain.
                  CH₃ - CH - COOH
                             
                             CHO
          2 - formly propanoic acid - 'C' of CHO not included in the name of main(parent) chain.  

Example - 1: CH₃CH₂OH
                        Principal functional group: -OH (-ol)
Parent hydride: CH₃ - CH₃
Parent hydride + one principal functional group → CH₃CH₂OH
^{Name of the compound →} 
Example - 2:   OH    OH
                                  
                         CH₂ - CH₂
Parent hydride + two principal functional groups  → OH     OH
                                                                                            
                                                                                     CH₂ - CH₂

                                 O
                                 
Example - 3: CH₃ - C - CH₂ - CH₂ - CH₂ - CH₂ - CH₂ - OH
Principal functional group >(C) = (O) - one
Parent hydride CH₃ - CH₂ - CH₂ - CH₂ - CH₂ - CH₂ - CH₃ Heptane
Parent hydride + Principal functional group
                                                                 O
                                                                 

   7           6           5           4            3          2      1
  CH₃  -  CH₂  -  CH₂  -  CH₂  -  CH₂  -  C  -  CH₃    Heptan - 2 - one  hydroxy
              Substituent  -  OH  -                                         
                                                                           O
                                                                           
  OH  -  CH₂  -  CH₂  -  CH₂  -  CH₂  -  CH₂  -  C  -  CH₃

Note: In the solution the principal functional group >C = O (keto) group is given more priority than to -OH (alcohol).
Example - 4:  CH₂ = CH - CH₂ - CH - CH₃
                                                     
                                                     OH

Parent hydride CH₃ -CH₂ -CH₂ -CH₂ -CH₃             Petane
Principal functional group -OH                                      - ol
Principal hydride + Principal functions                     Petan - 2 - ol
Subtractive modification (-2H)                                   -en

                                                      Cl
                                                       
                          8          7     6       5       4         3         2       1
Example - 5:   CH₂ = C = CH - CH - CH₂ - CH₂ - CH - CH₂
                                                                                    
                                                  Cl                          OH   OH

 

Example - 6:

 

IV: INFORMATION SKILLS AND PROJECTS

46. Collect information about Homologous series of alkanes about their molecular formula, structure and some physical properties.    (4 Marks)
A:                                                    Homologous series of Alkanes

Alkane	Molecular Formula	Strcuture	No. of Carbons	B.P. (ºC)	M.P. (ºC)	Density (gml at 20 ºC)
Methane	CH4	H - CH2-H	1	-164	-183	0.55
Ethane	C2H6	H-(CH2)2-H	2	-89	-183	0.51
Propane	C3H8	H-(CH2)3-H	3	-42	-189	0.50
Butane	C4H10	H-(CH2)4-H	4	0	-138	0.58
Pentane	C5H12	H-(CH2)5-H	5	36	-136	0.63

 The general formula of this homologous series Alkanes is C_nH_2n+2, where n = 1, 2, 3, .....

47. Collect information about Homologous series of Alkenes.    (2 Marks)
                                       Homologous series of Alkenes

Alkene	No. of Carbons	Structure	Formula
Ethene	2	CH2 = CH2	C2H4
Propene	3	CH3-CH = CH2	C3H6
Butene	4	CH3-CH2-CH = CH2	C4H8
Pentene	5	CH3-CH2-CH2-CH = CH2	C5H10

Alkenes have general molecular formula C_nH_2n, where n is 2, 3, 4.....

48. Draw the information information of homologous series of alkynes about their structures and some physical properties are not in a tabular form.       (2 Marks)
A:                                      Homologous series of Alkynes

Alkene	No. of Carbons	Structure	Formula
Ethene	2	HC CH	C2H2
Propene	3	CH3-C CH	C3H4
Butene	4	CH3-H2C-C CH	C4H6
Pentene	5	CH3-CH2-CH2-C  CH	C5H8

Alkynes have general molecular formula C_nH_2n-2 where 'n' is 2, 3, 4...

49. Collect information about suffixes and prefixes for some important characteristic functional groups and put it in a tabular form.     (4 Marks)
A: Suffixes and Prefixes for some important characteristic functional groups:

Class	Formula	Prefix	Suffix
Acid halides	-COX (where x is halogen atom)	halocarbonyl	Carbonyl halide
	-(C) O-X		Oylhalide
Alcohols	-OH	hydroxy	ol
Aldehydes	-CHO	formyl	Carbaldehyde
	- (C) HO	OXO	-al
Amides	CONH2	Carbamoyl	Carboxamide
	-(C) O NH2	OXO	-al
Amines	- NH2	amino	amine
Carboxylic acids	-COOH	Carboxy	Carboxylic acid
	-(C)OOH		oic acid
Ethers	-OR	(R) oxy
Esters	-COOR	Oxyearbonyl	(R)...Carboxylate
	(C)OOR	R-oxycarbonyl	(R)... oate
Ketones	-C = O	OXO	-one
Nitriles	-CN	cyno	-Carbonytrile
	-(C)N		Nitrile

Note: (C) designates a carbon atom included in the name of the parent hydride and does not belong to a group designated by a suffix or a prefix.

V. Communication through Drawing, Model making
50. Draw the shape of the Ethylene molecule.  (4 Marks)

       

    The common name for Ethene is Ethylene.

51. Draw the lattice structure of Diamond and diamond structure and explain briefly.       (4 Marks)
A: Diamond:
¤ In diamond each Carbon atom undergoes in its excited state sp³ hybridisation.
¤ Hence, each Carbon atom has a tetrahedral environment. the three dimensional structure of diamond is as shown:
                  
¤ As C - C bonds are very strong any attempt to distort the diamond structure requires large amount of energy.
¤ Hence diamond is one of the hardest materials known.
 

52. Draw a sketch of Buckminster fullerene. (₆₀C)
A:
                       
Buckminster fullerene (₆₀C) contains nearly spherical ₆₀C molecules with the shape of a soccer ball.

53. Draw the diagram of a soap molecule.
                   
 

Do You Know

¤ The concept of hybridisation was introduced by Linus Pauling (1931). The redistribution of orbitals of almost equal energy in individual atoms to give equal number of new orbitals with identical properties like energy and shape is called "hybridisation". The newly formed orbitals are called as 'hybrid orbitals'. 
¤ The buckminster fullerene, or usually just fullerene for short, was discovered in 1985 by a team of scientists Robert F.Curl, Harold W.Kroto and Richard E.Smalley from Rice University and the University of Sussex, three of whom were awarded the 1996 Nobel Prize in Chemistry. They are named so for the resemblance of their structure to the geodesic structures devised by the scientist and architect Richard Buckminster "Bucky" Fuller. 
 

Graphene - The new wonder material
             
       As its name indicates, graphene is extracted from graphite, the material used in pencils. Like graphite, graphene is entirely composed of carbon atoms. For a thickness of 1 mm graphite contains some 3 million layers of graphene. The carbons are perfectly distributed in a hexagonal honeycomb formation only in 0.3 nanometers thickness.
       Graphene conducts electricity better than copper. It is 200 times stronger that steel but six times lighter. It is almost perfectly transparent to light.

ABOUT SCIENTISTS 
Linus Pauling: The world's one of the greatest scientists and a great humanist. He was acknowledged as the most influential chemist.
      He is the only person ever to receive two unshared Nobel Prizes for Chemistry (1954) and for Peace (1962).
 

Wohler Friedrich (1800 - 1882) 
     German chemist who was a student of Berzelius. In attempting to prepare Ammonium cyanate from Silver cyanide and Ammonium chloride, he accidentally synthesized Urea in 1828. This was the first organic synthesis and shattered the vitalism theory.
     Wohler pursued the matter further and discovered that Urea and Ammonium cyanate had the same chemical formula, but very different chemical properties. This was an early discovery of isomerism, since Urea has the formula CO(NH₂)₂ and Ammonium cyanate has the formula NH₄CNO.