# What reactions occur when...?

## $\left(i\right)$ $\text{potassium is added to water...}$ $\left(i i\right)$ $\text{potassium chloride is added to water...}$

$i . K \left(s\right) + {H}_{2} O \left(l\right) \rightarrow K O H \left(a q\right) + \frac{1}{2} {H}_{2} \left(g\right) \uparrow$
$i i . K C l \left(s\right) r i g h t \le f t h a r p \infty n s {K}^{+} \left(a q\right) + C {l}^{_} \left(a q\right)$
Potassium metal undergoes oxidation with water to give hydrogen gas, and potassium hydroxide. Potassium chloride in aqueous solution forms aquated potassium and chloride ions, which do not affect the concentrations of ${H}_{3} {O}^{+}$ or $O {H}^{-}$ in solution. Reaction (i) is irreversible; reaction (ii) is reversible. Note that potassium chloride does not undergo reaction to form the hydroxide.