Question

A shiny brown colored element M on heating in the air forms a black solid N which dissolves by slowly pouring dilute hydrochloric acid on it. What will be the color of the resulting solution? Name M and predict the nature of N by writing the chemical equation of it with the acid.

Answer 1

Answer:

1. Element M is copper (Cu). When copper is heated in the air, it reacts with oxygen to form copper oxide which is black in colour.
2. The black solid N is copper oxide. When it is mixed with hydrochloric acid a neutralisation reaction takes place and copper chloride(salt) and water is formed. The colour of the solution thus obtained becomes blue-green due to the formation of copper chloride. Hence, N is basic in nature. This can be predicted beacuse N reacts with an acid to form salt and water which is similar to the naturalisation reaction between an acid and a base. Thus, it can be concluded that N is a basic oxide(basic in nature). Reaction is as follows:-

• $\rm{\underset{\text{Acid}}{2HCl}+\underset{\text{Base}}{CuO}\longrightarrow{}\underset{\text{Salt}}{CuCl_2}+\underset{\text{Water}}{H_2O}}$

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Additional Information:

Neutralisation reaction:-

• A chemical reaction in which an acid and base react each other to form salt and water. During a neutralisation reaction, both the acidity of the acid and basicity of the base is nullified. This means that there is no excess of hydrogen or hydroxide ions present in the solution.