# If the hydrogen ion concentration in a solution is 7.10 x 10^-5 mol/L, what is the pH?

$p H \cong 4$
$p H = - {\log}_{10} \left[{H}_{3} {O}^{+}\right]$.
We are given that $\left[{H}_{3} {O}^{+}\right] = 7.10 \times {10}^{-} 5 \cdot m o l \cdot {L}^{-} 1$.
And thus $p H = - {\log}_{10} \left(7.10 \times {10}^{-} 5\right) \cong 4$