Question

How many grams of $Ca{C}_2{O}_4$ will dissolve in distilled water to make one litre of unsaturated solution of it? ($K_{sp}$ for $Ca{C}_2{O}_4=2.5\times {10}^{-9}{mol}^2{lit}^{-2}$)

• A. $0.0064g$
• B. $0.1028g$
• C. $0.1280g$
• D. $0.2056g$

Answer 1

The correct option is A $0.0064g$

$Ca{C}_2{O}_4\rightleftharpoons C{a}^{2+}+C_2{O}_4^{2-}$

$S$ $S$

$K_{sp}=\left[C{a}^{2+}\right]\left[C_2{O}_4^{2-}\right]=\left[S\right]\left[S\right]=[S{]}^2=2.5\times {10}^{-9}$

$\left[S\right]=5\times {10}^{-5}M$

It means $5\times {10}^{-5}$ moles of $Ca{C}_2{O}_4$ will dissolve in 1 litre of unsaturated solution of it.

So $5\times {10}^{-5}\times 128=0.0064g$ of $Ca{C}_2{O}_4$ will dissolve in 1 litre of unsaturated solution of it.