Question

$C{a}^{2+}$ can be determined by precipitating it as $Ca{C}_2{O}_4$ gravimetrically. The percentage of $C{a}^{2+}$ in a sample, if 0.5 g of $C{a}^{2+}$ salt gave 1.28g of $Ca{C}_2{O}_4$ is
Given $(Ca=40,Ca=12,O=16)$

Answer 1

The molar mass of $Ca{C}_2{O}_4$ is $40+2\left(12\right)+4\left(16\right)=128g/mol$

Thus, 128 g $Ca{C}_2{O}_4$ corresponds to 40 g $C{a}^{2+}$.

Hence, 1.28 g $Ca{C}_2{O}_4$ will correspond to 0.4 g $C{a}^{2+}$.

Hence, the percentage of $C{a}^{2+}$ in the sample $=\frac{0.4g}{0.5g}\times 100=80$%.