Introduction to Acid-Base Reactions Practice Test

$\mathrm{CN^-}$ is the acid because it is negative

$\mathrm{HCN}$ donates $\mathrm{H^+}$ to $\mathrm{NO_2^-}$

$\mathrm{CN^-}$ donates $\mathrm{H^+}$ to $\mathrm{HNO_2}$

$\mathrm{HNO_2}$ donates $\mathrm{H^+}$ to $\mathrm{CN^-}$

$\mathrm{NO_2^-}$ donates $\mathrm{H^+}$ to $\mathrm{HCN}$