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ICSE Class 10 Chemistry Question 11 of 22

Solved 2016 Question Paper ICSE Class 10 Chemistry — Question 9

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Question

Question 4(b)

State your observations when ammonium hydroxide solution is added drop by drop and then in excess to each of the following solutions:

(i) copper sulphate solution

(ii) zinc sulphate solution.

Answer

(i) Pale blue precipitate of Cu(OH)2 is formed, which becomes deep blue when excess of ammonium hydroxide is added.

CuSO4 + 2NH4OH ⟶ (NH4)2SO4 + Cu(OH)2 ↓

Cu(OH)2 + (NH4)2SO4 + 2NH4OH [in excess] ⟶ 4H2O + [Cu(NH3)4]SO4

(ii) Gelatinous white precipitate of zinc hydroxide is formed which becomes colourless solution on adding excess of ammonium hydroxide.

ZnSO4 + 2NH4OH ⟶ (NH4)2SO4 + Zn(OH)2 ↓

Zn(OH)2 +(NH4)2SO4 + 2NH4OH [in excess] ⟶ 4H2O + [Zn(NH3)4]SO4