When solid lead nitrate is heated in a test tube, what is not observed during the reaction is:

a)a cracking sound is produced

b)a brown gas is produced

c)a light yellow substance is formed

d)a brown precipitate is formed

The correct answer is (d) A brow precipitate is produced.

The decomposition of lead nitrate is given as per the following equation

 2Pb(NO₃)_{2 (s)} → 2PbO _(s) + 4NO_{2 (g)} + O_{2 (g)}

This is accompanied by a crackling sound. Also it releases nitrogen dioxide which is a brown coloured gas. The residue that is left behind that is PbO, is yellow in colour.