Question

70. Give the chemical properties of acids and bases by giving balanced chemical equation.

Answer 1

Acids are those substances that furnish hydrogen$\left({\mathrm{H}}^{+}\right)$ ions in their aqueous solution while bases are those substances that produce hydroxide$\left({\mathrm{OH}}^{-}\right)$ ions in their aqueous solution.

Part 1: Chemical properties of acids

1. Reaction with metals

• Some metals react with strong acids and displace hydrogen from strong acids to form hydrogen gas.
• Such metals which displace hydrogen from strong acids are known as active metals.
• Example: Zinc reacts with sulphuric acid (H₂SO₄) to produce zinc sulphate (ZnSO₄) along with the evolution of hydrogen gas (H₂).

$\underset{\mathrm{Zinc}}{\mathrm{Zn}\left(\mathrm{s}\right)}+\underset{\mathrm{Sulphuric}\mathrm{acid}}{{\mathrm{H}}_2{\mathrm{SO}}_4\left(\mathrm{aq}\right)}\to \underset{\mathrm{Zinc}\mathrm{sulphate}}{{\mathrm{ZnSO}}_4\left(\mathrm{aq}\right)}+\underset{\mathrm{Hydrogen}}{{\mathrm{H}}_2\left(\mathrm{g}\right)\uparrow }$

2. Reaction with metal oxide

• Metal oxides react with all dilute mineral acids to generate their corresponding metallic salts and water.
• Example: Calcium oxide (CaO) reacts with nitric acid (HNO₃) leading to the formation of calcium nitrate [Ca(NO₃)₂] and water (H₂O).

$\underset{\mathrm{Calcium}\mathrm{oxide}}{\mathrm{CaO}}+\underset{\mathrm{Nitric}\mathrm{acid}}{2{\mathrm{HNO}}_3}\to \underset{\mathrm{Calcium}\mathrm{nitrate}}{\mathrm{Ca}{\left({\mathrm{NO}}_3\right)}_2}+\underset{\mathrm{Water}}{{\mathrm{H}}_2\mathrm{O}}$

3. Reaction with metal carbonate

• Metal carbonates react with acid leading to the formation of salt and water along with carbon dioxide evolution.
• Since the salt is produced along with water. So, these reactions come under the category of neutralization reactions.
• Example: Magnesium carbonate reacts with Sulphuric acid leading to the formation of Magnesium sulphate and water along with the evolution of carbon dioxide.

$\underset{\mathrm{Magnesium}\mathrm{carbonate}}{{\mathrm{MgCO}}_3}+\underset{\mathrm{Sulphuric}\mathrm{acid}}{{\mathrm{H}}_2{\mathrm{SO}}_4}\to \underset{\mathrm{Magnesium}\mathrm{sulphate}}{{\mathrm{MgSO}}_4}+\underset{\mathrm{Water}}{{\mathrm{H}}_2\mathrm{O}}+\underset{\mathrm{Carbon}\mathrm{dioxide}}{{\mathrm{CO}}_2}$

Part 2: Chemical properties of bases

1. Action of heats

• Some hydroxide readily decomposes on slight heating.
• When ammonium hydroxide is slightly heated, it quickly decomposes into ammonia gas and water. The chemical reaction of decomposition of ammonium hydroxide can be represented as:

$\underset{\mathrm{Ammonium}\mathrm{hydroxide}}{{\mathrm{NH}}_4\mathrm{OH}\left(\mathrm{aq}\right)}\stackrel{∆}{\to }\underset{\mathrm{Ammonia}}{{\mathrm{NH}}_3\left(\mathrm{g}\right)}+\underset{\mathrm{Water}}{{\mathrm{H}}_2\mathrm{O}\left(\mathrm{l}\right)}$

• Some hydroxide decomposes on strong heating.
• When aluminum hydroxide is strongly heated, it decomposes into aluminum oxide and water. The chemical reaction of decomposition of aluminum hydroxide can be represented as:

$\underset{\mathrm{Aluminum}\mathrm{hydroxide}}{2\mathrm{Al}{\left(\mathrm{OH}\right)}_3}\stackrel{∆}{\to }\underset{\mathrm{Aluminum}\mathrm{oxide}}{{\mathrm{Al}}_2{\mathrm{O}}_3}+\underset{\mathrm{Water}}{{\mathrm{H}}_2\mathrm{O}}$