Question

1. Write two observations when lead nitrate is heated in a test tube
2. Name the type of reaction
3. Write a balanced chemical equation to represent the above reaction

Answer 1

1)i) When Lead nitrate is heated it produces a yellow precipitate of Lead monoxide.

ii) It also produces a brownish colored fume (gas) which is Nitrogen dioxide along with oxygen.

2) This is Decomposition type of chemical reaction. Decomposition reaction is a reaction which in compound is decomposed into its constituent compounds.

3) The balanced chemical equation for this reaction is 2 Pb(NO3)2 (s) produces 2 PbO (s) + 4NO2 + O2 (g). 2Pb(NO3)2 = 2PbO + 4NO2 + O2. It is thermal decomposition reaction.

Answer 2

Decomposition Reaction:

• When a compound breaks to form two or more products on heating, the reaction is called a thermal decomposition reaction.
• Such decomposition reactions take place only at high temperatures.
• The reactants absorb most of the heat energy supplied. This results in the breaking of some bonds and the formation of new bonds.
• Example: Calcium carbonate $(CaCO_{3})$ on exposure to high temperatures, decomposes into calcium oxide$(CaO)$ or quicklime, and carbon dioxide$(CO_{2} )$.

Explanation:

1. When lead nitrate$(Pb(NO_{3}) _{2})$ is heated in a test tube, it gets decomposed and forms lead oxide$(PbO)$, nitrogen dioxide$(NO_{2})$, and oxygen gas$(O_{2})$.
2. Due to the lead oxide, the solution turns yellow, and reddish-brown fumes are observed.
3. The type of reaction is thermal decomposition.
4. The balanced chemical equation for the decomposition of lead nitrate is as follows: $2Pb(NO_{3}) _{2}$ → $2PbO+4NO_{2}+O_{2}$

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