Question

A solution containing CaCl2 is mixed with a solution of Li2C2O4 to form a solution that is 3.5 × 10-4 M in calcium ion and 2.33 × 10-4 M in oxalate ion. What will happen once these solutions are mixed? Ksp (CaC2O4) = 2.3 × 10-9.

Answer 1

This is an incomplete question, here is a complete question.

A solution containing CaCl₂ is mixed with a solution of Li₂C₂O₄ to form a solution that is 3.5 × 10⁻⁴ M in calcium ion and 2.33 × 10⁻⁴ M in oxalate ion. What will happen once these solutions are mixed? Ksp (CaC₂O₄) = 2.3 × 10⁻⁹

A. Nothing will happen since both calcium chloride and lithium oxalate are soluble compounds.

B. Nothing will happen Ksp > Q for all possible precipitants.

C. A precipitate will form as calcium oxalate is not soluble to any extent.

D. A precipitate will form since Q > Ksp for calcium oxalate.

Answer : The correct option is, (D) A precipitate will form since Q > Ksp for calcium oxalate.

Explanation :

Concentration of
`Ca^(2+)` =
`3.5* 10^(-4)M`

Concentration of
`C_2O_4^(2-)` =
`2.33* 10^(-4)M`

The equilibrium chemical reaction will be:

`CaC_2O_4\rightleftharpoons Ca^(2+)+C_2O_4^(2-)`

The solubility constant expression for this reaction is:

`K_(sp)=[Ca^(2+)][C_2O_4^(2-)]=2.3* 10^(-9)`

Now we have to calculate the ionic product for calcium oxalate.

`Q_(sp)=[Ca^(2+)][C_2O_4^(2-)]`

`Q_(sp)=(3.5* 10^(-4))* (2.33* 10^{-4)`

`Q_(sp)=8.2* 10^(-8)`

From this we conclude that,
`Q_(sp)>K_(sp)` that means a white solid precipitate of calcium oxalate will be formed when the solutions are mixed.

Hence, the correct option is, (D)