# What is the pH of a solution that has a [H+] = 0.0039 M?

$\approx 2.41$
$p H = - {\log}_{10} \left[{H}^{+}\right]$
$p H = - {\log}_{10} \left[0.0039\right]$
$p H = 2.4089 \approx 2.41$