Question

Give one example each of which illustrates the following characteristics of a chemical reaction:

change of colour

Answer 1

When blue coloured copper sulphate reacts with hydrogen sulphide gas, a black coloured substance copper sulphide is formed.

\[\ce{\underset{\text{copper sulphate solution, blue}}{CuSO4} + \underset{\text{hydrogen sulphide}}{H2S} ->\underset{\text{copper sulphide black solid}}{CuS} +\underset{\text{sulphuric acid}}{H2SO4}}\]