Question

A solution is saturated with respect to $Sr{CO}_3$ and $Sr{F}_2$. The ${CO}_3^{2-}$ was found to be $1.2\times {10}^{-3}M$. The concentration of $F^{-}$ in the solution would be:

• A. $1.3\times {10}^{-3}M$
• B. $2.6\times {10}^{-2}M$
• C. $3.7\times {10}^{-2}M$
• D. $5.8\times {10}^{-7}M$

Answer 1

The correct option is C $3.7\times {10}^{-2}M$

Solution is saturated with respect to $SrC{O}_3$ so $\left[S{r}^{2+}\right]=\left[C{O}_3^{2-}\right]=1.2\times {10}^{-3}M$.

$K_{sp}=\left[S{r}^{2+}\right][F^{-}{]}^2$

$7.9\times {10}^{-10}=1.2\times {10}^{-3}\times [F^{-}{]}^2$

$[F^{-}{]}^2=3.7\times {10}^{-2}M$.