Question

Given below are two statements:
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 \( K_b \) value of acid and the base forming it.
In the light of the above statements, choose the most appropriate answer from the options given below:

• A. Both Statement I and Statement II are correct
• B. Statement I is correct but Statement II is incorrect
• C. Both Statement I and Statement II are incorrect
• D. Statement I is incorrect but Statement II is correct

Answer 1

The Correct Option is A

The question provides two statements to analyze, and we need to determine the validity of each statement. 

1. Understanding Statement I: "Aqueous solution of ammonium carbonate is basic."
   • Ammonium carbonate is the salt formed from a weak acid (carbonic acid, \(H_2CO_3\)) and a weak base (ammonia, \(NH_3\)).
   • In aqueous solution, ammonium carbonate dissociates into ammonium ions \((NH_4^+)\) and carbonate ions \((CO_3^{2-})\).
   • The carbonate ion is capable of undergoing hydrolysis to produce hydroxide ions \((OH^-)\), making the solution basic:
2. Reasoning for Statement II: "Acidic/basic nature of salt solution of a salt of weak acid and weak base depends on \(K_a\) and \(K_b\) value of acid and the base forming it."
   • The relative values of the acid dissociation constant \((K_a)\) for the conjugate acid and the base dissociation constant \((K_b)\) for the conjugate base determine the pH of the solution.
   • If \(K_b > K_a\), the solution tends to be basic. Conversely, if \(K_a > K_b\), the solution is typically acidic.
   • For ammonium carbonate, the basicity due to the carbonate ion (since it has a higher affinity for protons compared to the hydrolysis of the ammonium ion) usually prevails, leading to a slightly basic solution.

Given these considerations, both statements are accurate:

• Statement I is correct because the carbonate ion's hydrolysis makes the aqueous solution of ammonium carbonate basic.
• Statement II is correct as it appropriately describes the dependence on \(K_a\) and \(K_b\) values for salts derived from weak acids and bases.

Conclusion: The correct answer is that both Statement I and Statement II are correct.

Answer 2

Statement I: Ammonium carbonate (NH₄)₂CO₃ is basic in solution because it forms a weak acid (NH₄⁺) and a weak base (CO₃^2-). The carbonate ion (CO₃^2-) can accept protons, making the solution basic.

Statement II: This statement is also correct as the pH of a salt solution formed from a weak acid and a weak base depends on the relative values of K_a and K_b.

So, Statement I and II both are correct.