Question

5.
A reddish brown metal turns black when heated in air. The reaction is reversed when
hydrogen gas is passed over the above formed black substance. Mention the type of reactions
taking place in each case.
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Answer 1

The metal is Copper...

When copper metal is heated, it reacts with oxygen to form black coloured copper oxide.

2Cu+ O2-------> 2CuO

(Combination Reaction)

When H2 is passed, it combines with the O2 thus leaving behind copper metal.

CuO + H2---------> Cu + H2O

(Single displacement, Redox Reaction)