Answer the following questions:

1. Write two chemical properties of an acid.

2. Write two chemical properties of the base.

3. Write two chemical properties of salt.

4. Deduce pH + pOH = 14

5. Explain the importance of pH in the digestion of food.

6. Write chemical equations for four neutralisation reactions.

1. Two properties of acids are are as follows:

•The reaction of the acid with metal:

Acids on reaction with metals produce dihydrogen gas and salt corresponding to the metal.

Acid + metal → salt + dihydrogen gas

•The reaction of acid with base:

Salt and water are formed when acids react with bases. This reaction is called a neutralisation reaction.

Acid + Base → salt + water

2. two properties of bases are as follows:

•The reaction of the base with acid:

Salt and water are formed when acids react with bases. This reaction is called a neutralization reaction.

Acid + Base → salt + water

•The reaction of the base with non-metal oxide

This reaction is also similar to the reaction of base with acids. Salt and water are produced in this reaction also.

Base + Non-metal oxide → salt + water

3. two properties of salts are as follows:

•Salt reacts with other acids to form another salt and acid

Salt + acid → other salt + acid

•Salt reacts with another base to form other salt and base.

Salt + base → other salt + base

4. pH = -log₁₀[H ⁺ ]

pOH = -log₁₀[OH^-]

Since the distilled water is neutral,

[H ⁺ ] = [OH^-] = 10^-7

[H ⁺ ] × [OH^-] = 10^-7 × 10^-7

[H ⁺ ] × [OH^-] = 10^-14

Taking negative logarithm on both sides,

-log₁₀[H ⁺ ] - log₁₀[OH^-] = -log₁₀[10^-14]

pH + pOH = 14

5. As the food enters the stomach, hydrochloric acid is secreted. This decreases the pH in the stomach. The pH in the stomach turns between 1 and 3. In the decreased pH, the enzyme pepsin becomes active and helps in the process of digestion.

6. When a reaction takes place between an acid and a base, salt and water are produced. This reaction is called a neutralisation reaction. In this reaction acid and base mutually nullify each other’s properties.

Four such reactions are as follows:

•HCl + NaOH → NaCl + H₂O

•CH₃COOH + NH₄OH → CH₃COONH₄ + H₂O

•HNO₃ + KOH → KNO₃ + H₂O

•H₂SO₄ + 2KOH → K₂SO₄ + 2H₂O