Answer
The pH value of milk is about $6.8$.
Work Step by Step
First, note that the hydrogen ion concentration of milk is about $1.6\times {{10}^{-7}}$moles per liter.
Thus, $\left[ {{\text{H}}^{\text{+}}} \right]=1.6\times {{10}^{-7}}$.
Substitute it in the formula $\text{pH}=-\log \left[ {{\text{H}}^{\text{+}}} \right]$ as follows:
$\begin{align}
& \text{pH}=-\log \left[ {{\text{H}}^{\text{+}}} \right] \\
& \text{pH}=-\log \left[ 1.6\times {{10}^{-7}} \right] \\
\end{align}$
Therefore:
$\begin{align}
& \text{pH}=-\log \left[ 1.6\times {{10}^{-7}} \right] \\
& \text{pH}\approx -\left( -6.795 \right) \\
& \text{pH}\approx 6.795
\end{align}$
