Question

Assertion $\left(A\right):$ Aqueous solution of Ammonium carbonate is basic

Reason $\left(R\right):$ Acidic/basic nature of a salt solution of a salt of weak acid and weak base depends on $K_a$ and $K_b$ value of the acid and base forming it.

• A. $A$ is true but $R$ is false.
• B. Both $A$ and $R$ are true and $R$ is the correct explanation of $A.$
• C. Both $A$ and $R$ are true but $R$ is not the correct explanation of $A.$
• D. $A$ is false but $R$ is true.

Answer 1

The correct option is B

Both $A$ and $R$ are true and $R$ is the correct explanation of $A.$

Analyzing the assertion

It is correct because aqueous solution of ammonium carbonate is basic in nature.

Analyzing the reason

It is also correct because for a solution of salt of weak acid and weak base, the acidic/basic nature depends upon value of $K_a$ for weak acid and $K_b$ for weak base.

Solution is basic if

$K_b$ (weak base) $>K_a$ (weak acid).

$Ka\left(H_{2}C{O}_3\right)=4.3\times {10}^{-7}$

$Kb\left(N{H}_{4}OH\right)=1.8\times {10}^{-5}$

$K_b$ (Ammonium hydroxide) $>K_a$ (Hydrogen carbonate)

$\therefore$ Hence, solution of Ammonium carbonate is basic in nature.

Both $A$ and $R$ are true and $R$ is the correct explanation of $A.$

$\therefore$ Correct answer is option $\left(A\right).$