Calculate the solubility of CuX (Ksp=[Cu2+][X2−]=1.27×10−36) in a solution that is 0.200 M in NaCN.

I have already tried to square root the Ksp value to get the answer but it was wrong.

The solubility of CuX is 1.425x10⁻⁷M

Explanation:

Given:

initial concentration of NaCN=0.2M

Ksp=1.27x10⁻³⁶

The reaction are:

CuX → Cu²⁺ + X²⁺, Ksp=1.27x10⁻³⁶

Cu²⁺ + 4CN⁻ → (Cu(CN)₄)²⁻, Kf=1x10²⁵

The overall reaction is:

CuX + 4CN⁻ → (Cu(CN)₄)²⁻ + X²⁺

The equilibrium constant is:

K=Ksp*Kf=1.27x10⁻³⁶*1x10²⁵=1.27x10⁻¹¹

              CuX      +        4CN⁻      →       (Cu(CN)₄)²⁻ +        X²⁺

I              -                      0.2                    0                         0

C            -                       -4                     +x                        +x

E             -                      0.2-4                x                          x

The equation for equilibrium is:

Here, solving for x:

x=1.425x10⁻⁷M=CuX

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