Question

$HCN\left(aq\right)\to H^{+}\left(aq\right)+C{N}^{-}\left(aq\right)$

According to above reaction, the Hydrocyanic acid dissociates, find the acid dissociation constant for $HCN$?

• A. $\frac{\left[H^{+}\right]\left[C{N}^{-}\right]}{\left[HCN\right]}$
• B. $\left[H^{+}\right]\left[C{N}^{-}\right]\left[HCN\right]$
• C. $\frac{\left[HCN\right]}{\left[H^{+}\right]\left[C{N}^{-}\right]}$
• D. $\frac{\left[H^{+}\right]}{\left[HCN\right]\left[C{N}^{-}\right]}$
• E. $\frac{1}{\left[HCN\right]\left[H^{+}\right]\left[C{N}^{-}\right]}$

Answer 1

The correct option is A $\frac{\left[H^{+}\right]\left[C{N}^{-}\right]}{\left[HCN\right]}$

The expression for the acid dissociation constant for $HCN$ is $\frac{\left[H^{+}\right]\left[C{N}^{-}\right]}{\left[HCN\right]}$. It is the ratio of product concentrations to reactant concentrations.