Question

Write two observations when lead nitrate is heated in a test tube.
(i) Name the type of reaction.
(ii) Write the balanced chemical equation to represent the above reaction.

Answer 1

Hint: Chemical formula of lead nitrate is $Pb(N{O}_3{)}_2$. To answer this question, refer to the decomposition reactions of metal nitrates. To balance a chemical equation of a reaction, count the total number of atoms of each element on both sides, that is, the reactant side and product side of the reaction and make them equal.

Complete step by step answer:
Given that lead nitrate, having chemical formula $Pb(N{O}_3{)}_2$ is heated in a test tube. The two observations of this chemical reaction are:
(i) When lead nitrate is heated, it decomposes into lead oxide ($PbO$), nitrogen dioxide ($N{O}_2$), and oxygen gas ($O_2$). The type of this reaction is thermal decomposition reaction.
(ii) The thermal decomposition reaction of lead nitrate to give lead oxide, nitrogen dioxide and oxygen, is represented with a balanced chemical equation as:
$2Pb(N{O}_3{)}_2(s)\stackrel{\mathrm{\Delta }}{\to }2PbO(s)+4N{O}_2(g)+O_2(g)$
Thus, this is the required answer.

Additional information:
Reddish brown fumes of nitrogen dioxide ($N{O}_2$) is formed on heating lead nitrate. Lead oxide (PbO) also produced, is a solid of buff yellow colour. Thus, the colour of residue obtained after thermal decomposition of lead nitrate is yellow. Lead nitrate is toxic, and its ingestion may lead to acute lead poisoning, and it is applicable for all soluble lead compounds.

Note: Lead nitrate is an inorganic compound and is nitrate salt of lead. Most nitrates tend to decompose on heating to give the metal oxide, brown fumes of nitrogen dioxide, and oxygen as products. But, most metal oxides decompose upon heating, to produce metal oxide and brown coloured nitrogen dioxide and oxygen. You must know that lead (IV) oxide is thermally unstable and it tends to decompose into lead (II) oxide and oxygen upon heating.