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Question
Give two examples where a chemical reaction is accompanied by a change in colour of the reactants and products on completion of the reaction.
Solution
(i) \[\ce{\underset{\text{magnesium}}{Mg} + \underset{\text{Blue copper sulphate}}{CuSO4} ->\underset{\text{colourless magnesium sulphate}}{MgSO4}+\underset{\text{copper}}{Cu}}\]
(ii) \[\ce{2Pb[NO3]2->\underset{\text{litharge (yellow)}}{2PbO} + 4NO2 + O2}\]
(iii) \[\ce{\underset{\text{colourless}}{Pb[NO3]} + 2Kl->\underset{\text{yellow ppt.}}{Pbl2 v} + 2KNO3}\]
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