Chemistry
Ammonia solution in water gives a blue precipitate when it combines with a solution of copper salt. The blue precipitate further dissolves in excess of ammonia solution to give an azure blue solution. Explain with equation.
Answer
Ammonia solution in water gives a blue precipitate when it combines with a solution of copper salt, due to the formation of Cu(OH)2
CuSO4 + 2NH4OH ⟶ (NH4)2SO4 + Cu(OH)2 ↓
The pale blue precipitate of copper hydroxide dissolves in excess of ammonium hydroxide forming tetraamine copper [II] sulphate, an azure blue soluble complex salt.
Cu(OH)2 + (NH4)2SO4 + 2NH4OH ⟶ [Cu(NH3)4]SO4 + 4H2O
Related Questions
A gas 'P' gives dense white fumes with chlorine. It's aqueous solution gives a blue colour with copper (II) hydroxide. Give the name and formula of the gas P.
Give reasons for the following —
(a) Liquid ammonia is used as a refrigerant in ice plants.
(b) Aqueous solution of ammonia is used for removing grease stains from woollen clothes.
(c) Aqueous solution of ammonia gives a pungent smell.
(d) Aqueous solution of ammonia conducts electricity.
Give chemical equation(s) to prove that NH3 contains nitrogen and hydrogen?
Copy and complete the following equations.
(a) AlN + H2O ⟶
(b) 2NH3 + 3PbO ⟶
(c) NH3 + 3Cl2 ⟶
(d) NH3 + CO2 ⟶
(i) Which property of ammonia is illustrated by equation (c)?
(ii) What important fertiliser is prepared from equation (d)? State the conditions.