Question

Give an example of a reaction in which colour change occurs.

Answer 1

Colour change reactions

• Some reactions are characterised by change in colour.
• For example, When Zinc metal is dissolved in Copper Sulphate, blue colour of solution changes to colourless because copper is replaced by zinc and zinc sulphate is formed.

$\underset{\underset{\left(\mathrm{Grey}\right)}{\mathrm{Zinc}}}{\mathrm{Zn}\left(\mathrm{s}\right)}+\underset{\underset{\left(\mathrm{Blue}\right)}{\mathrm{Copper}\mathrm{Sulphate}}}{{\mathrm{CuSO}}_4\left(\mathrm{aq}\right)}\to \underset{\underset{\left(\mathrm{Colourless}\right)}{\mathrm{Zinc}\mathrm{Sulphate}}}{{\mathrm{ZnSO}}_4\left(\mathrm{aq}\right)}+\underset{\underset{\left(\mathrm{Brown}\right)}{\mathrm{Copper}}}{\mathrm{Cu}\left(\mathrm{s}\right)}$