Calculating the pH of a saturated calcium fluoride solution How can I calculate the pH of a saturated solution of calcium fluoride ($\ce{CaF2}$)? I am given the following values:

$$\begin{align}
K_\mathrm{sp}(\ce{CaF2}) &amp;= 3.9 \cdot 10^{-11} \\
K_\mathrm{a}(\ce{HF}) &amp;= 6.8 \cdot 10^{-4} \\
K_\mathrm{w} &amp;= 10^{-14}
\end{align}$$

(The $K_\mathrm{sp}$ and $K_\mathrm a$ values are taken from the appendices of Skoog et al. Fundamentals of Analytical Chemistry, 9th edition.)
In homework land you are right, but not in real life.

The $K_\mathrm b$ of $\ce{Ca^2+}$ ($\mathrm pK_\mathrm b = 2.43$ according to some sources) is within 1 log unit of the $K_\mathrm a$ of $\ce{HF}$.  In other words, near neutral pH, consideration of the $\ce{Ca^2+/CaOH+}$ equilibrium is almost as important as the $\ce{F-/HF}$ equilibrium.