When potassium cyanide reacts with water, the resulting solution will be

When potassium cyanide reacts with water, the resulting solution will be alkaline.

The reaction of water with potassium cyanide, $\mathit{KCN}$, produces potassium hydroxide which is alkaline in nature. The equilibrium reaction between $\mathit{KCN}$ and water can be represented as below:
$\mathit{KCN}+H_{2}O\rightleftharpoons K^{+}+C{N}^{-}+H^{+}+O{H}^{-}$
$H^{+}+C{N}^{-}\rightleftharpoons \mathit{HCN}$
$K^{+}+O{H}^{-}\rightleftharpoons \mathit{KOH}$

The salt of a strong base and a weak acid is potassium cyanide. The substance reacts with water, creating a potent base that has a corrosive reaction. A strong base $\mathit{KOH}$ is produced via the anionic hydrolysis of $\mathit{KCN}$. The odour of potassium cyanide is bitter, and it is also very explosive. Such compounds need to be handled with prudence.