JAMB Chemistry 2019 Paper

Concept:Nitrates (trioxonitrates(V)) decompose on heating, but sodium nitrate gives oxygen without nitrogen(IV) oxide impurity.Explanation:Heating nitrates of Pb, Zn, or Ca gives $\mathrm{NO_2}$ mixed with oxygen, for example: $$2\mathrm{Pb(NO_3)_2(s)} \xrightarrow{\Delta} 2\mathrm{PbO(s)} + 4\mathrm{NO_2(g)} + \mathrm{O_2(g)}$$Sodium trioxonitrate(V), $\mathrm{NaNO_3}$, decomposes to give oxygen directly: $$2\mathrm{NaNO_3(s)} \xrightarrow{\Delta} 2\mathrm{NaNO_2(s)} + \mathrm{O_2(g)}$$Hence, sodium nitrate is the best starting material for oxygen preparation.Answer:D. Na