Question

Write sequential observation for effect of heat on
(a) copper nitrate
(b) lead carbonate
(c) ammonium chloride.

Answer 1

The effects of heat on the given compounds are as follows:
(a) Copper nitrate: When this compound is heated, colourless oxygen gas along with light brown-coloured nitrogen dioxide is released. Besides this, black-coloured copper oxide is left behind as a residue.

$$\begin{gathered} 2\mathrm{Cu}{\left({\mathrm{NO}}_3\right)}_2\stackrel{\mathrm{\Delta }}{\to }2\mathrm{CuO}+4{\mathrm{NO}}_2+{\mathrm{O}}_2 \\ \mathrm{Black}\mathrm{residue}\mathrm{Reddish}\mathrm{brown}\mathrm{gas} \end{gathered}$$

(b) Lead carbonate: When this compound is heated, colourless carbon dioxide gas is released, which turns lime water milky. Besides this, yellow-coloured lead oxide is left behind as a residue.

$$\begin{gathered} {\mathrm{PbCO}}_3\stackrel{\mathrm{\Delta }}{\to }\mathrm{PbO}+{\mathrm{CO}}_2 \\ \mathrm{Yellow}\mathrm{residue}\mathrm{Turns}\mathrm{lime}\mathrm{water}\mathrm{milky} \end{gathered}$$

(c) Ammonium chloride: When ammonium chloride is heated, no residue is left. Ammonia and hydrogen chloride gases are formed, which chemically combine to form white fumes of ammonium chloride.

NH₄Cl + Δ ⇌ NH₃ + HCl