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Chapter – 2: Acids, Bases and Salts
ACIDS
These are the substances which have sour taste.
They turn blue litmus solution red.
They give H⁺ ions in aqueous solution.
The term ‘acid’ has been derived from the Latin word, acidus, which means sour.
Strong Acids: HCl, H₂SO₄, HNO₃
Weak Acids: CH₃COOH, Oxalic acid, Lactic acid
BASES
These are the substances which are bitter in taste and soapy in touch.
They turn red litmus solution blue.
They give OH⁻ ions in aqueous solution.
Strong Bases: NaOH, KOH, Ca(OH)₂
Weak Bases: NH₄OH
SALTS
These are the compounds formed from reaction of acid and base.
Example: NaCl, KCl
INDICATORS
These are the substances which change their colour/smell in different types of substances.
Natural Indicators
S. No. Indicator Acidic Basic
1 Litmus Red Blue
2 Red cabbage Red Green
3 Hydrangea Blue Pink
4 Turmeric No change Red
Synthetic Indicators
S. No. Indicator Acidic Basic
1 Phenolphthalein Colourless Pink
2 Methyl orange Red Yellow
Olfactory Indicators
S. No. Indicator Acidic Basic
1 Onion Smell No smell
2 Vanilla Retains No smell
3 Clove oil Retains Loses smell
Reactions of Acids and Bases
a) Reaction of acids and bases with metals
Acids, in general, react with metals to produce salt and hydrogen gas. Bases, in general, do not react with metals and
do not produce hydrogen gas.
Acid + active metal → salt + hydrogen + heat
2HCl + Mg → MgCl2 + H2 (↑)
Hydrochloric acid + Magnesium → Magnesium chloride + Hydrogen
Base + metal → salt + hydrogen + heat
2NaOH + Zn → Na2ZnO2 + H2 (↑)
Sodium hydroxide + Zinc → Sodium zincate + Hydrogen
Hydrogen gas released can be tested by bringing a burning candle near gas bubbles; it bursts with a
pop sound.
b) Reaction of acids with metal carbonates and bicarbonates
Acids produce carbon dioxide, as well as metal salts and water, when they react with metal carbonates or metal
bicarbonates. Sodium chloride, carbon dioxide, and water are formed when sodium carbonate interacts with
hydrochloric acid. Allowing carbon dioxide gas to travel through lime water turns it milky.
Acid + metal carbonate or bicarbonate → salt + water + carbon dioxide.
2HCl + CaCO3 → CaCl2 + H2O + CO2
H2SO4 + Mg (HCO3)2 → MgSO4 + 2H2O + 2CO2
Effervescence indicates the liberation of CO2 gas.
Chapter – 2: Acids, Bases and Salts
ACIDS
These are the substances which have sour taste.
They turn blue litmus solution red.
They give H⁺ ions in aqueous solution.
The term ‘acid’ has been derived from the Latin word, acidus, which means sour.
Strong Acids: HCl, H₂SO₄, HNO₃
Weak Acids: CH₃COOH, Oxalic acid, Lactic acid
BASES
These are the substances which are bitter in taste and soapy in touch.
They turn red litmus solution blue.
They give OH⁻ ions in aqueous solution.
Strong Bases: NaOH, KOH, Ca(OH)₂
Weak Bases: NH₄OH
SALTS
These are the compounds formed from reaction of acid and base.
Example: NaCl, KCl
INDICATORS
These are the substances which change their colour/smell in different types of substances.
Natural Indicators
S. No. Indicator Acidic Basic
1 Litmus Red Blue
2 Red cabbage Red Green
3 Hydrangea Blue Pink
4 Turmeric No change Red
Synthetic Indicators
S. No. Indicator Acidic Basic
1 Phenolphthalein Colourless Pink
2 Methyl orange Red Yellow
Olfactory Indicators
S. No. Indicator Acidic Basic
1 Onion Smell No smell
2 Vanilla Retains No smell
3 Clove oil Retains Loses smell
Reactions of Acids and Bases
a) Reaction of acids and bases with metals
Acids, in general, react with metals to produce salt and hydrogen gas. Bases, in general, do not react with metals and
do not produce hydrogen gas.
Acid + active metal → salt + hydrogen + heat
2HCl + Mg → MgCl2 + H2 (↑)
Hydrochloric acid + Magnesium → Magnesium chloride + Hydrogen
Base + metal → salt + hydrogen + heat
2NaOH + Zn → Na2ZnO2 + H2 (↑)
Sodium hydroxide + Zinc → Sodium zincate + Hydrogen
Hydrogen gas released can be tested by bringing a burning candle near gas bubbles; it bursts with a
pop sound.
b) Reaction of acids with metal carbonates and bicarbonates
Acids produce carbon dioxide, as well as metal salts and water, when they react with metal carbonates or metal
bicarbonates. Sodium chloride, carbon dioxide, and water are formed when sodium carbonate interacts with
hydrochloric acid. Allowing carbon dioxide gas to travel through lime water turns it milky.
Acid + metal carbonate or bicarbonate → salt + water + carbon dioxide.
2HCl + CaCO3 → CaCl2 + H2O + CO2
H2SO4 + Mg (HCO3)2 → MgSO4 + 2H2O + 2CO2
Effervescence indicates the liberation of CO2 gas.
