Question

(a) Design an activity to demonstrate the decomposition reaction of lead nitrate.

(b) Draw labelled diagram of the experimental set-up. List two main observations.

(c) Write balanced chemical equation for the reaction stating the physical state of the reactant and the products.

Answer 1

Activity to demonstrate the decomposition reaction of lead nitrate Pb(NO₃)₂

(a)

• Take about 2g of lead nitrate powder in a boiling tube.
• Hold the boiling tube with a pair of tongs and heat it over a flame, as shown in the figure.
• What do you observe? Note down the change, if any. 

(b)

 

Two main observations:

1. The emission of brown fumes of NO₂ after thermal decomposition of Pb(NO₃)₂.
2. The colourless compound Pb(NO₃)₂ forms a yellow compound PbO and brown fumes of NO₂ gas.

(c)

$$\underset{(\mathrm{Lead}\mathrm{nitrate})(\mathrm{solid})}{2\mathrm{Pb}(\mathrm{NO}{\phantom{A}}_3){\phantom{A}}_2{\phantom{A}}_{(\mathrm{s})}}\stackrel{\mathrm{Heat}}{\to }\underset{(\mathrm{Lead}\mathrm{oxide})(\mathrm{solid})}{2\mathrm{PbO}{\phantom{A}}_{(\mathrm{s})}}+\underset{(\mathrm{Nitrogen}\mathrm{dioxide})(\mathrm{gas})}{4\mathrm{NO}{\phantom{A}}_2{\phantom{A}}_{(\mathrm{g})}}+\underset{(\mathrm{Oxygen})(\mathrm{gas})}{\mathrm{O}{\phantom{A}}_2{\phantom{A}}_{(\mathrm{g})}}$$