Answer
a) Basic.
b) Acidic.
c) Essentially neutral.
d) Basic.
Work Step by Step
a) $Na_2SO_4$: Strong base $(NaOH)$ and weak acid $(HS{O_4}^-)$: Basic solution.
b) $NH_4Cl$: Weak base $(NH_3)$ and strong acid $(HCl)$: Acidic solution.
c) $KCl$: Strong base $(KOH)$ and strong acid $(HCl)$: Neutral solution.
d) $NH_4CN$: Weak base $(NH_3)$ and weak acid: $(HCN)$: We need to compare the constants values:
$K_b (NH_3) > K_a ( HCN)$:
Therefore: Basic solution.
