A red-brown metal X forms a salt XSO4. When hydrogen sulphide gas is passed through an aqueous solution of XSO4, then a black precipitate of XS is formed alongwith sulphuric acid solution.
(a) What could the salt XSO4 be?
(b) What is the colour of salt XSO4?
(c) Name the black precipitate XS.
(d) By using the formula of the salt obtained in (a) above, write an equation of the reaction which takes place when hydrogen sulphide gas is passed through its aqueous solution.
(e) What type of chemical reaction takes place in this case?
(a) The salt XSO4 is CuSO4.
(b) The colour of the salt CuSO4 is blue.
(c) The black precipitate XS is copper sulphide (CuS).
(d) CuSO4 + H2S → CuS + H2SO4
(e) Double displacement reaction takes place in this case.
Lakhmir Chemistry 2013