Problem: a. Using the Ksp value for Cu(OH)2 (1.6 x 10-19) and the overall formation constant for Cu(NH3)42+ (1.0 x 1013), calculate the value for the equilibrium constant for the following reaction:Cu(OH)2 (s) + 4NH3 (aq) ⇌ Cu(NH3)42+(aq) + 2OH -(aq)b. Use the value of the equilibrium constant you calculated in part a to calculate the solubility (in mol/L) of Cu(OH)2 in 5.0 M NH3. In 5.0 M NH3 the concentration of OH - is 0.0095 M.

FREE Expert Solution

(A) Add the two equations below: 

Eqn 1 : Cu(OH)2(s) Cu2+ (aq) + 2 OH(aq) (Ksp)

Eqn 2 : Cu2+ (aq) + 4 NH3 (aq) [Cu(NH3)4]2+(aq) (formation constant)

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Cu(OH)2 (s) + 4NH3 (aq) ⇌ Cu(NH3)42+(aq) + 2OH -(aq)


We added the equations and it became exactly the overall equation.

This means we can simply multiply the constants to get the overall constant. 

Keq = Ksp ×KfKeq = (1.6 × 10-19) ×(1.0 × 1013)

Keq = 1.6x10-6 


(b) Use the Keq expression to calculate the solubility

Recall: Solids are ignored


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Problem Details

a. Using the Ksp value for Cu(OH)2 (1.6 x 10-19) and the overall formation constant for Cu(NH3)42+ (1.0 x 1013), calculate the value for the equilibrium constant for the following reaction:

Cu(OH)2 (s) + 4NH3 (aq) ⇌ Cu(NH3)42+(aq) + 2OH -(aq)

b. Use the value of the equilibrium constant you calculated in part a to calculate the solubility (in mol/L) of Cu(OH)2 in 5.0 M NH3. In 5.0 M NH3 the concentration of OH - is 0.0095 M.

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