Question

# A metal M does not liberate hydrogen from acids but reacts with oxygen to give a black color product. Identify M and black colored product and also explain the reaction of M with oxygen.

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Solution

## Reaction of Copper with Acid:Copper $\left(\mathrm{Cu}\right)$ lies below hydrogen in the reactivity series. Thus it will not react with Sulfuric acid or Hydrochloric acid and hence there will be no evolution of Hydrogen$\left({\mathrm{H}}_{2}\right)$ gas.$\underset{\mathrm{Copper}}{\mathrm{Cu}\left(\mathrm{s}\right)}+\underset{\mathrm{Hydrochloric}\mathrm{acid}}{\mathrm{HCl}\left(\mathrm{aq}\right)}\to \mathrm{No}\mathrm{reaction}$Reaction of Copper with Oxygen:The reaction of Copper$\left(\mathrm{Cu}\right)$ with oxygen$\left({\mathrm{O}}_{2}\right)$ produces a black-colored copper oxide $\left(\mathrm{CuO}\right)$.The chemical reaction can be depicted as: $2\mathrm{Cu}\left(\mathrm{s}\right)+{\mathrm{O}}_{2}\left(\mathrm{g}\right)\to 2\mathrm{CuO}\left(\mathrm{s}\right)$It is an example of a combination reaction.Hence, M is Copper and the black-colored product is Copper oxide.

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