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 – copper carbonate.

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:

Copper carbonate CuCO₃ → CuO + CO₂[g]

Colour change:

Copper carbon [CuCO₃] – Green – to Copper [III] oxide [CuO] – Black