Question

A chemical reaction is often accompanied by external indications or characteristics which include – 

1. Colour change
2. Effervescence or gas evolved
3. Evolution or absorption of heat
4. Formation of a precipitate.

With reference to each of the above indications, state the external indication seen during – Thermal decomposition of mercury [II] oxide.

Answer 1

Thermal decomposition of mercury [II] oxides: Red colour of Hg[II]0 changes to silvery (Hg metal).