JEE Chemistry 2024 Question with Solution

Given: Two statements about the nature of aqueous ammonium carbonate solution and the criterion for salts formed from a weak acid and a weak base.

Find: Which option correctly identifies the truth values of Statement I and Statement II.

For ammonium carbonate, the ions present in water are $NH_4^+$ and $CO_3^{2-}$. The carbonate ion undergoes hydrolysis and produces basic character in solution. Hence, the aqueous solution of ammonium carbonate is basic.

For a salt formed from a weak acid and a weak base, the acidic or basic nature of the solution depends on the relative magnitudes of $K_a$ and $K_b$. If $K_b > K_a$, the solution is basic, while if $K_a > K_b$, the solution is acidic.

Therefore, Statement I is correct and Statement II is also correct.

The correct option is A.

Given:

• Statement I: Aqueous solution of ammonium carbonate is basic.
• Statement II: Acidic/basic nature of salt solution of a salt of weak acid and weak base depends on $K_a$ and $K_b$ values of the acid and the base forming it.

Find: The most appropriate option.

Analysis of Statement I: Ammonium carbonate is a salt of weak acid $H_2CO_3$ and weak base $NH_3$. In aqueous solution, it dissociates into $NH_4^+$ and $CO_3^{2-}$. The carbonate ion hydrolyses in water and generates basic character, so the solution becomes basic.

Analysis of Statement II: For salts derived from a weak acid and a weak base, the pH depends on the relative strengths represented by $K_a$ and $K_b$. The larger of these two determines whether the solution is acidic or basic.

Since both statements are correct, the correct answer is A.