Liebig was born in Germany in 1803. His father was a dealer of Paints and Varnishes. Liebig neglected other subjects for his great interest in Chemistry. He later attracted the attention of all in his university education. This he missed in his school education.
       Liebig's students and grand students were also awarded Nobel Prize. Among other scientists, Liebig is one who defined that acids in variably contain Hydrogen.
 

Key Words - Explanations
Indicators: Indicators are substances or solutions to detect the nature of the given solution for acidity or basidity.
Acids : Acids are sour to taste and turn blue litmus to red litmus.
e.g.: HCl, H₂SO₄ etc..,
Bases: Bases are soapy to touch and turn red litmus to blue litmus.
e.g.: NaOH, Mg(OH)₂ etc..,
Red litmus: It is an indicator and turns blue in basic medium.
Blue litmus: It is an indicator and turns red in acidic medium.
Phenolphthalein: It is also an indicator in liquid state which is colourless. It remains colourless in acidic medium and becomes pink in colour in basic medium.
Methyl orange: It is also an indicator. It turns to red in acidic medium and becomes yellow in basic medium.
Salts: It is produced as a result of neutralization reaction between an acid and a base.
Neutralization: It is the reaction between an acid and a base to produce salt and water.
Guard tube: Guard tube is a drying tube used in experiments.
Hydronium ion: Hydrogen ions cannot exist as bare ions. They associate with water molecules and exist as hydrated ions with each H+ attached by 4 to 6 water molecules. For this we represent H+ as hydronium ion, H3O+ (H++ H2O  H3O+).
Alkali: Bases which are soluble in water are called alkalis.
Strong acid: A strong acid has more H₃O⁺ ions.
e.g.: HCl, H₂SO₄ etc..,
Strong base: A strong base has more OH^- ions.
e.g.: NaOH, KOH etc ..,
Universal Indicator: Universal Indicator is a mixture of several indicators. The universal indicator shows different colours at different concentrations of hydrogen ions in a solution.
pH Scale: A scale for measuring hydrogen ion concentration in a solution is called pH Scale (The 'p' in pH stands for 'Potenz'. German 'Potenz' is Power).
Potenz: In German 'Potenz' means Power.
Antacids: Antacids are mild bases which neutralize the excess acid in the stomach.
Tooth decay: Bacteria present in the mouth produce acids by degradation of sugar and food particles remaining in the mouth. This causes corrosion of tooth resulting in tooth decay.
Family of Salts: Salts having the same positive or negative radicals belong to a family known as family of Salts.
Common Salt: It is Sodium Chloride salt.
Bleaching powder: Bleaching powder is produced by the action of Chlorine on dry slaked lime. [Ca(OH)₂]. It is represents by the formula CaOCl₂.
Baking Soda: Baking Soda is Sodium hydrogen carbonate (NaHCO₃). This is some times added for faster cooking. It is a mild non-corrosive base.
Washing Soda: Washing Soda is Na₂CO₃.10 H₂O. This is Sodium carbonate. It is used for removing permanent hardness of water.
Hydrated salt: Salt which contains water.
Water of crystallization: Water of crystallization is the fixed number of water molecules present in one formula unit of a salt.
Plaster of Paris: On careful heating of Gypsum (CaSO₄. 2 H₂O) at 373 K it loses water molecules partially to become Calcium sulphate hemihydrate (CaSO₄ .  H₂O). This is called Plaster of Paris.
Dilution: Mixing of an acid or base with water result in decrease in the concentration of ions (H₃O⁺/ OH^-) per unit volume. Such process is called dilution.
 

SYNOPSIS 

❈  Acids are sour to taste and turn blue litmus to red.
❈  Bases are soapy to touch and turn red litmus to blue.
❈  Litmus solution is a dye extracted from lichen, a plant belonging to the division of Thallophyta and is used as an indicator.
❈  There are some substances whose odour changes in acidic or basic media. These are called olfactory indicators.
 

❈  When acids react with metals like Zinc, Hydrogen gas is liberated.
❈  Similarly when bases react with metals like Zinc then also Hydrogen gas is released.
❈  When acids react with carbonates and Hydrogen Carbonates, carbon dioxide gas is released.
❈  Metal Carbonate + acid → Salt + Water + Carbon dioxide
❈  Na₂CO₃ (s) + 2 HCl (aq) → 2 NaCl (aq) + H₂O (l) + CO₂ (g)
❈  Metal Hydrogen carbonate + Acid → Salt + Water + Carbon dioxide
❈  NaHCO₃ (s) + HCl (aq) → NaCl (aq) + H₂O (l) + CO₂(g)
❈  The reaction of an acid with a base to give a salt and water is known as a neutralization reaction.
       Base + Acid → Salt + Water
❈  Reaction of metal oxides with acids also produces salt and water.
   Metal oxide + Acid → Salt + Water
❈  Non metal oxides are acidic in nature.
❈  Metal oxides are basic in nature.
❈  Acids produce Hydrogen ions H⁺ in solution; which are responsible for their acidic properties.
❈  On dissolving bases in water produces hydroxide (OH^-) ions.
❈  Bases which are soluble in water are called alkalies.
❈  All bases do not dissolve in water.
❈  Hydrogen ions cannot exist as bare ions. They associate with water molecules and exist as hydrated ions with each H⁺ attached by 4 to 6 water molecules.
❈  For this we represent H⁺ as hydronium ions H₃O⁺.
❈  Mixing of an acid or base with water result in decrease in the concentration of ions (H₃O⁺/ OH^-) per unit volume. Such a process is called dilution and the acid or the base is said to be diluted.
❈  The process of dissolving an acid or a base in water is an exothermic process.
❈  Acid must always be added slowly to water with constant stirring.
❈  If water is added to concentrated acid, the heat generated may cause the mixture to splash out and cause burns.
❈  The glass container may also break due to excessive local heating.
❈  A strong acid will have more H₃O⁺ ions.
❈  A strong base will have more OH^- ions.
❈  An acid is considered to be a strong acid if it has more H₃O⁺ ions. If it contains fewer H₃O⁺ ions then it is a weak acid.
❈  Universal indicator are used to know the strength of acid or base.
❈  Universal indicator is a mixture of several indicators.
❈  The universal indicator shows different colours at different concentrations of Hydrogen ions in a solution.
❈  The universal indicator can also be used to know the strength of acid or base.
❈  A scale for measuring Hydrogen ion concentration in a solution is called pH scale.
❈  The pH of neutral solution is 7. Values less than 7 on the pH scale represent an acidic solution.
❈  As pH value increases from 7 to 14, it represents a decrease in H₃O⁺ ion concentration or an increase in OH^- ion concentration in the solution.
❈  pH value of a solution above 7 represents a basic solution.
❈  Living organism can survive only in a narrow range of pH change.
❈  When pH of rain water is less than 5.6, it is called acid rain.
❈  Tooth decay starts when the pH of the mouth is lower than 5.5.
❈  Our stomach produces Hydrochloric acid. It helps in the digestion of food without harming the stomach.
❈  Antacids are used to get rid of the pain in the stomach due to acidity.
❈  Plants require a specific pH range for their healthy growth.
❈  Bee sting leaves an acid which causes pain and irritation at the place where it stings.
❈  NaCl and Na₂SO₄ belong to the family of Sodium Salts.
❈  NaCl and KCl belong to the family of 'Chloride Salts'.
❈  Salts of a strong acid and a strong base are neutral and the pH value is 7.
❈  The salts of a strong acid and a weak base are acidic and the pH value is less than 7.
❈  The salts of a strong base and weak acid are basic in nature and the pH value is more than 7.
❈  Sea water contains many salts dissolved in it.
❈  Sodium Chloride is the predominant component and it is separated from the other salts in Sea water.
❈  Sodium Chloride is known as table salt.
❈  Deposits of solid salt are found in several parts of the world. This is called rock salt.
❈  Rock salt is mined like coal.
❈  Common salt is an important raw material for various materials of daily use. Such as NaOH, NaHCO₃, Na₂CO₃, CaOCl₂ etc..,
❈  The fixed number of water molecules present in one formula unit of a salt is called water of crystallization.
❈  Plaster of Paris is obtained on heating Gypsum at 373 K.
❈  Plaster of Paris is used by doctors as a plaster for supporting fractured bones in the right position.
 

Writer : C.V. SARVESWARA SARMA