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?

A. A precipitate will form as calcium oxalate is not soluble to any extent.
B. A precipitate will form since Q > Ksp for calcium oxalate.
C. Nothing will happen since both calcium chloride and lithium oxalate are soluble compounds.
D. Nothing will happen Ksp > Q for all possible precipitants.

Answer 1

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

Step-by-step explanation:

Ksp of CaC₂O₄ is:

CaC₂O₄(s) ⇄ Ca²⁺ + C₂O₄²⁻

Where Ksp is defined as the product of concentrations of Ca²⁺ and C₂O₄²⁻ in equilibrium:

Ksp = [Ca²⁺][C₂O₄²⁻] = 2.27x10⁻⁹

In the solution, the concentration of calcium ion is 3.5x10⁻⁴M and concentration of oxalate ion is 2.33x10⁻⁴M.

Replacing in Ksp formula:

[3.5x10⁻⁴M][2.33x10⁻⁴M] = 8.155x10⁻⁸. This value is reaction quotient, Q.

If Q is higher than Ksp, the ions will produce the precipitate CaC₂O₄ until [Ca²⁺][C₂O₄²⁻] = Ksp.

Thus, right answer is:

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