chem QQQQQuestion

Q1

(1) is incorrect.
When the mixture is heated, the copper reacts with oxygen in the air to give a black solid of copper(II) oxide.
2Cu + O2 → 2CuO
Therefore, copper(II) is left, but no gas is formed.

(2) is correct.
The oxide of copper dissolves in the acid, but copper does not react. After filtration, the residue obtained is copper.

(3) is incorrect.
Both copper and copper(II) oxide reacts with concentrated sulphuric acid to form a solution of copper(II) sulphate. The gas evolved is sulphur dioxide.
CuO + H2SO4 → CuSO4 + H2O
Cu + 2H2SO4 → CuSO4 + 2H2O + SO2

Q2

(1) is correct.
The aqueous solution of copper(II) ions is blue.

(2) is correct.

(3) is incorrect.
Chlorine ions are colourless, but not yellow. When concentrated hydrochloric acid is added to a solution of copper(II) sulphate, a green solution is formed. This is due to the formation of green [CuCl42-] complex.
Cu2+(aq) + 4Cl-(aq) → [CuCl42-](aq)
=

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