Question

Calculate the molar solubility of CuX(Ksp=1.27×10?36) in each of the following.

Part A

pure water

Express your answer using three significant figures.

Part B

0.25 M CuCl2

Express your answer using two significant figures.

Part C

0.23 M Na2X

Express your answer using two significant figures.

Answer 1

1) The dissociation of salt CuX in aqueous solution takes place as follows:

CuX(s) <--->Cu²⁺(aq) +X^2-(aq)

Ksp1.27*10^-36[Cu2+][X^2-]

Let the molar solubility of CuX in pure water be S,

[Cu2+][X^2-]S

1.27*10^-36[Cu2+][X^2-]S^2

or, S1.127*10^-18M

part B) In 0.25M CuCl2 solution, CuCl2 <--->Cu2+(aq) +2Cl-

[Cu2+]0.25M+S 0.25M (as S<<<0.25M)

So,Ksp1.27*10^-36[Cu2+][X^2-](0.25M)*S

or ,Molar Solubility,S(1.27*10^-36)/0.255.08*10^-36M

part C) In 0.23M Na2X, Na2X <--->2Na+(aq) + X^2-(aq)

[X^2-]0.23+S0.23M (S<<<0.23M)

Ksp1.27*10^-36[Cu2+][X^2-](0.23M)*S

or ,Molar Solubility,S(1.27*10^-36)/0.235.522*10^-36M