Question

A salt 'X' is dissolved in water of pH=7. The resulting solution becomes alkaline in nature. The salt is made up of:

• A. A strong acid and strong base
• B. A strong acid and weak base
• C. A weak acid and weak base
• D. A weak acid and strong base

Answer 1

The correct option is D A weak acid and strong base

The Solution becomes Alkaline. Hence, the Base of which the salt is made up of must be strong.
Therefore, the salt is a Salt of Weak Acid and Strong Base.
Following are the four types of salts and the nature of resulting solution when they are mixed with water:
Salt of Strong Acid and Strong Base: Neutral. eg: $NaCl,KCl,N{a}_{2}SO4$
Salt of Strong Acid and Weak Base: Acidic. eg: $N{H}_{4}Cl$
Salt of Weak Acid and Strong Base: Basic or Alkaline. eg: $C{H}_{3}COONa$
Salt of Weak Acid and Weak Base: Cannot be predicted theoretically as it depends on values of $K_a$ and $K_b$ of corresponding components. eg: $C{H}_{3}COON{H}_4$