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CRITICAL THINKING


1. In the case homologous series of alkanes, which one of the following statements is incorrect
A. The members of the series are isomers of each other
Explanation: The difference between any two successive members of the homologous series -CH 2 - i.e., the molecular weight of every two adjacent members differ by 14.
(CH2 = 12 + 2 = 14)

 

2. How many primary, secondary, tertiary and quaternary carbons are present in the following hydrocarbon
CH3 - CH(CH3) - C(CH3)2 - CH2 - CH(CH3) - CH2 - CH3
A. Primary Secondary Tertiary Quaternary
               6                 2               2               1
Explanation:

1o  ⇒ Primary 6, 2o  ⇒ Secondary 2
3o  ⇒ Tertiary 2, 4o  ⇒ Quanternar y 1

3. The octane number of a sample of petrol is 40. It means that its knocking property is equal to the mixture of
A. 60% n-heptane + 40% iso-octane
Explanation : Octane number of fuel is the percentage of iso- octane in mixture.

 

4. Formation of 2-butene as major product by dehydration of 2-butanol is according to
A. Saytzeff rule
Explanation:

According to this rule H atom goes from that b – carbon which is less hydrogenated.

 

 

5. 

A. O3
Explanation:

 

6. Which of the following is Friedel-Craft's reaction
(a) C6H6 + FeCl3 + Cl2  C6H5Cl
(b) C6H6CHO + CH3CHO + KOH  C6H5CH = CH-CHO

(c) 
(d) C6H5OH + CHCl3 + KOH Salicylaldehyde

A.
Explanation: Friedel-craft's reaction

 

7. Condition for maximum yield of C2H5Cl is
A.  
Explanation:

 

8. When ethyl alcohol is heated with red phosphorus and HI, then which of the following is formed
(a) C2H6  (b) CH4   (c) C3H8    (d) C2H4
A. C2H6
Explanation:

 

9. In the Fischer-Tropsch synthesis of petrol..... and ..... are used as the raw materials
A. H2 ;CO
Explanation: Fischer-Tropsch Process

 

10. Which one of the following reactions is most suitable for the preparation of n-propyl benzene
(a) Friedel-Craft's reaction (b) Wurtz reaction
(c) Wurtz-Fittig reaction (d) Grignard reaction
A. Wurtz-Fittig reaction

Explanation:

 

11. Propane cannot be prepared from which reaction
A. 
Explanation: Hydroboration of alkenes followed by hydrolysis in basic medium yield alcohols and not the alkanes.

 


A. Koch reaction
Explanation:
Koch reaction : (Carboxylation of Alkene)

 

13. The compound   on reaction with NaIO4 in the presence of KMnO4 gives
A. CH3COCH3 + CH3CHO
Explanation:


                       

 


A. Ag2C2
Explanation:

 

15. Naphthalene is a/an
A. Molecular solid
Explanation: Naphthalene is a molecular solid. If the crystals contains only individuals atoms; as in solid argon or krypton or if they are composed of non polar molecules as in naphthalene, the only attraction between the molecules are the London forces.

 

16. Which of the following is not aromatic
A. 1, 3, 5 heptatriene
Explanation: A compound is said to be aromatic if it is planar and there is complete delocalization of p electrons, which is only possilble if it is a conjugated cyclic system and number of electrons used in delocalization is (4n + 2) . 1, 3, 5 heptatriene is not an aromatic compound because complete delocalization of p electrons, is not possible in it.

 

17. Acetylene reacts with HCN in the presence of Ba(CN)2 to yield
A. Vinyl cyanide
Explanation:

 

18. Write the products of the addition reaction C = C + XY  
A. 
Explanation: Addition reaction means addition on double bond.

 

19. Formation of polyethylene from calcium carbide takes place as follows
CaC2 + 2H2O  Ca(OH)2 + C2H2
C2H2 + H2   C2H4
n(C2H4)   (-CH2 - CH2 -)n
The amount of polyethylene obtained from 64.1 kg CaC2 is
A. 28 kg

Explanation:

64g of CaC2 gives 28g of ethylene
∴ 64kg of CaC2 will give 28kg of polyethylene

20. Nitrobenzene can be prepared from benzene by using a mixture of conc. HNO3 and conc. H2SO4. In the nitrating mixture, HNO3 acts as a
A. Base
Explanation:

 

21. A group which deactivates the benzene ring towards electrophilic substitution but which directs the incoming group principally to the o- and p-positions is
A. -Cl
Explanation: Electron accepting groups which make the substitution difficult are known of deactivating groups. the group or substituent already present on the ring also decides the position of incoming group. ortho and para directing groups are as follow
-CH3 ,C2H5 (-R),-NH2 ,-OH , halogens, (Cl,Br, I)

 

22. Which order is correct for the decreasing reactivity to ring monobromination of the following compounds
        C6H5CH3 ,      C6H5COOH ,       C6H6        C6H5 NO2
                I                       II                    III                    IV
A. I > III > II > IV
Explanation:

 

23. Benzene is obtained by
A. Polymerisation of three C2H2 molecules
Explanation: Polymerisation


                        

 

24. Toluene can be oxidised to benzoic acid by
A. K2Cr2O7
Explanation:


                   

 

25.   Identify A and B in the given reaction
A. C2H2 and CH3CHO

Explanation: Wohler reaction :


 

26. The compound X on reaction with HgSO4 + H2SO4 gives Y which on oxidation gives acetic acid. X is
A: (a) C2H2
Explanation :

 

27. What is formed when calcium carbide react with heavy water
A: (a) C2D2

Explanation: CaC2 + 2D2O     C2D2 + Ca(OD)2

28. The addition of HBr is easiest with
A. (CH3)2 C = CH2
Explanation: It is a unsymmetrical olefin. In such cases addition of H - X is governed by 'Markownikoff's rule'

 

29. Identify the species X in the reaction :
Propene + O (conc. acidic KMnO4 ) X + Formic acid
A. Acetic acid
Explanation:

 

30. In benzene 1, 3 position is called
A. Meta
Explanation:

    
1, 2 or 1, 6 = ortho
1, 3 or 1, 5 = meta
1, 4 = para.

Posted Date : 19-02-2021

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