Question

How many grams of $Ca{C}_2{O}_4$ will dissolve in distilled water to make one litre of saturated solution
$(K_{sp}=2.5\times {10}^{-9}$ and its molecular mass is $128)$

• A. $0.0064g$
• B. $0.0128g$
• C. $0.0032g$
• D. $0.0640g$

Answer 1

Answer: (A)

$0.0064g$

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

$K_{sp}=[S{]}^2=2.5\times {10}^{-9}$

$\left[S\right]=5\times {10}^{-5}$ It means $5\times {10}^{-5}$moles of $Ca{C}_2{O}_4$ will dissolve in distilled water to make one litre of saturated solution.

$Mass=Moles\times Molarmass$

= $5\times {10}^{-5}\times 128=0.0064g$

So 0.0064g of $Ca{C}_2{O}_4$ will dissolve in distilled water to make one litre of saturated solution.