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[問題] Chemistry 問題

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Chemistry 問題

Ammonia dissolves readily in water to form a weakly alkaline solution. A solution M was obtained by slowly adding aqueous ammonia to copper (II) sulphate solution (with stirring) until the ammonia was in excess.
(a) In terms of chemical equilibrium, explain why aqueous ammonia is weakly alkaline, and write an appropriate ionic equation.
(b) Describe and explain, with the aid of ionic equations, what would be observed in the above experiment.
(c) What would be observed if dilute sulphuric acid were slowly added to the mixture M, until the acid was in excess? Explain the observation.

我想問既係part c
Answer: The deep blue colour gradually becomes lighter, and a blue precipitate would be observed, which dissolves in excess dilute sulphuric acid to form a blue solution.
Shifting the equilibrium position:
Cu(OH)2+4NH3-->[Cu(NH3)4]2+ + 2OH-
to the left/dilute H2SO4 removes the NH3, so the complex changes back to Cu(OH)2.
我想問點解dilute H2SO4 會remove NH3 instead of OH-?!
   

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