CBSE Class 10 Science 2020 · Paper 31/4/2 · Question 15(a)
When hydrogen sulphide gas is passed through a blue solution of copper sulphate, the colour of the solution fades and a black precipitate is obtained.
- (a)Name the type of reaction mentioned above.
- (b)Why does the colour of the solution fade away ?
- (c)Write the chemical name of the black precipitate formed.
- (d)Give the balanced chemical equation for the reaction involved.
Answer
It is a double displacement (precipitation) reaction: copper leaves as black copper sulphide, and colourless sulphuric acid remains, so the blue colour fades.
(a) It is a double displacement reaction (it is also a precipitation reaction).
(b) The blue colour is due to copper sulphate; its copper is removed as insoluble copper sulphide and colourless sulphuric acid forms in the solution, so the colour fades.
(c) Copper sulphide, (copper(II) sulphide).
(d)
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