Given below are two statements: 

Assertion (A): An aqueous solution of ammonium carbonate is basic.
Reason (R):

The acidic or basic nature of a salt solution of a salt of a weak acid and a weak base depends on the Ka and Kb values of the acid and the base forming it.

1. Both (A) and (R) are true and (R) is the correct explanation of (A).
2. Both (A) and (R) are true but (R) is not the correct explanation of (A).
3. (A) is true but (R) is false.
4. (A) is false but (R) is true.
Hint: Kb of NH4OH>Ka of H2CO3
The reaction is as follows:
 
If Kb of NH4OH>Ka of H2CO3
The solution is basic.
or, If Ka of H2CO3>Kb of NH4OH; the solution is acidic.  Hence, both assertion and reason are true and the reason is the
correct explanation of assertion.