Question

A chemical reaction is generally accompanied by certain external indications or characteristics. These include – change of – (a) colour (b) state (c) smell (d) evolution of gas (e) formation of precipitate (f) evolution or absorption of heat. With reference to change of colour – state the change in colour seen when the following are heated –  lead [IV] oxide.

Answer 1

Change of colour — In certain chemical reactions a change of colour is seen to be observed. Heat on substances to observe change in colour of reactants and products.

Heat on:

Lead [IV] oxide 2PbO₂→2PbO + O₂ [g]

Colour change:

Lead [IV] oxide [PbO] – Brown – to Lead monoxide [PbO] – Yellow.