Question

Consider reversible reaction,
$HCN(aq)H^{+}(aq)+C{N}^{-}(aq)$
At equilibrium the addition of $C{N}^{-}(aq)$ would

• A. decrease the $H^{+}(aq)$ ion concentration
• B. reduce HCN (aq) concentration
• C. increase the equilibrium constant
• D. decrease the equilibrium constant

Answer 1

Answer: (A)

For the reaction
$HCN(aq)\rightleftharpoons H^{+}(aq)+C{N}^{-}(aq)$
$K_c=\frac{\left[H^{+}\right]\left[C{N}^{-}\right]}{[HCN]}$
On the addition of $C{N}^{-}(aq)$ at equilibrium, the $\left[H^{+}\right](aq)$ decrease to maintain the equilibrium constant.