Question

$5g$ each of $Ca{CO}_3$ and $Sr{CO}_3$ was shaken well in a litre of water. Concentration of ${Ca}^{2+},{Sr}^{2+}$ and ${CO}_3^{2-}$ will be:
$K_{{sp}_{Ca{CO}_3}}=4.8\times {10}^{-9}$ and $K_{{sp}_{Sr{CO}_3}}=1.1\times {10}^{-10}$.

• A. $\left[{Ca}^{2+}\right]=7.0\times {10}^{-5}M$, $\left[{Sr}^{2+}\right]=1.50\times {10}^{-6}M$, $\left[{CO}_3^{2-}\right]=6.85\times {10}^{-5}M$
• B. $\left[{Ca}^{2+}\right]=1.50\times {10}^{-6}M$, $\left[{Sr}^{2+}\right]=7.0\times {10}^{-5}M$, $\left[{CO}_3^{2-}\right]=6.85\times {10}^{-5}M$
• C. $\left[{Ca}^{2+}\right]=6.85\times {10}^{-5}M$, $\left[{Sr}^{2+}\right]=1.50\times {10}^{-6}M$, $\left[{CO}_3^{2-}\right]=7.0\times {10}^{-5}M$
• D. None of these

Answer 1

The correct option is C $\left[{Ca}^{2+}\right]=6.85\times {10}^{-5}M$, $\left[{Sr}^{2+}\right]=1.50\times {10}^{-6}M$, $\left[{CO}_3^{2-}\right]=7.0\times {10}^{-5}M$

$\left[C{a}^{2+}\right]=\sqrt{K_{sp\left(CaC{O}_3\right)}}=\sqrt{4.8\times {10}^{-9}}=6.85\times {10}^{-5}M$

$\left[C{O}_3^{2-}\right]=\frac{K_{sp\left(CaC{O}_3\right)}}{\left[C{a}^{2+}\right]}=\frac{4.8\times {10}^{-9}}{6.85\times {10}^{-5}M}=7.0\times {10}^{-5}M$

$\left[S{r}^{2+}\right]=\frac{K_{sp\left(SrC{O}_3\right)}}{\left[C{O}_3^{2-}\right]}=\frac{1.1\times {10}^{-10}}{7.0\times {10}^{-5}}=\left[{Sr}^{2+}\right]=1.50\times {10}^{-6}M$