Question

17. (a) When the powder of a common metal is heated in an open china dish, its colour turns black. However, when hydrogen is passed over the hot
black substance so formed, it regains its original colour. Based on this information answer the following questions:
(i) What type of chemical reaction takes place in each of the two given steps?
(ii) Name the metal initially taken in the
powder form.
Write balanced chemical equations for both the reactions.
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Answer 1

(i) : In the first place oxidation reaction takes place

In the second place , decomposition takes place

(ii) : Copper is the metal taken in powder form which turns black on getting oxidised .

2Cu + O2 = 2CuO

CuO + H2 = Cu + H2O