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JAMB Chemistry 2007 Question 9

Question 9

Chemical Equilibrium

Cu2+(aq) + 4NH3(g) ⇌ [Cu (NH3)4]2+(aq)
In the reaction above, what is the effect of precipitating Cu2+(aq) as CuS(s)?

  1. A.NH3(g) concentration will decrease.
  2. B.More NH3(g) will be generated.
  3. C.The equilibrium will shift to the right.
  4. D.There will be no effect.
Show the answer and explanation

Answer: B (More NH3(g) will be generated.)

Explanation

By Le Chatelier's principle, removing a reactant (Cu2+) makes the equilibrium shift to the left to replace it, so the complex breaks up and more NH3 is produced.