Answer
$0.10M$ $KCN$ is more basic.
Work Step by Step
** You can find the $K_b$ values on table: 14.2 (Page 624)
Since both solutions have the same concentration, we just have to determine which compound is more basic:
-$NH_3$:
$NH_3$ is a base with $K_b = 1.8 \times 10^{-5}$
- $KCN$:
It is a salt formed by $K^+$ and $CN^-$.
$K^+$ has negligible acidity, so, we don't need to consider it.
$CN^-$ is a base with $K_b = 3.0 \times 10^{-5}$
$CN^-$ has a greater $K_b$ value, therefore, it is more basic.
So, $0.10M$ $KCN$ is more basic.
