# What is [H3O+] for a 0.500 M solution of hydrochloric acid? Make sure you include the ionization equation.

$\left[{H}_{3} {O}^{+}\right] = 0.500 \cdot m o l \cdot {L}^{-} 1$
$H C l \left(a q\right) + {H}_{2} O \left(l\right) \rightarrow {H}_{3} {O}^{+} + C {l}^{-}$
And thus a $0.500 \cdot m o l \cdot {L}^{-} 1$ solution of $H C l \left(a q\right)$ is STOICHIOMETRIC in ${H}_{3} {O}^{+}$ and $C {l}^{-}$, i.e. $\left[{H}_{3} {O}^{+}\right] = \left[C {l}^{-}\right] = 0.500 \cdot m o l \cdot {L}^{-} 1$.