Question

State what you observe when:
(i) Neutral litmus solution is added to alkaline solution.
(ii) Ammonium hydroxide is added to iron (III) sulphate solution.
(iii) Lead nitrate and sodium chloride are mixed.
(iv) Ethane is bubbled through a solution of bromine in tetrachloromethane (carbon tetrachloride).
(v) Sulphur burns.

Answer 1

(i) Alkaline solution contains hydroxyl ions. Thus, when neutral litmus solution is added to an alkaline solution, the solution turns blue.

(ii) On reaction with ammonium hydroxide, iron (III) sulphate forms reddish brown precipitate of iron (III) hydroxide, which is insoluble in excess ammonium hydroxide.

${\mathrm{Fe}}_2{\left({\mathrm{SO}}_4\right)}_3+6{\mathrm{NH}}_4\mathrm{OH}\to 2\mathrm{Fe}{\left(\mathrm{OH}\right)}_3+3{\left({\mathrm{NH}}_4\right)}_2{\mathrm{SO}}_4$

(iii) Lead nitrate reacts with sodium chloride to form a chalky white precipitate of lead chloride, which is soluble in hot water.

$\mathrm{Pb}{\left({\mathrm{NO}}_3\right)}_2+2\mathrm{NaCl}\to {\mathrm{PbCl}}_2+2{\mathrm{NaNO}}_3$

(iv) When ethane is bubbled through a solution of bromine in carbon tetrachloride, the brown coloured bromine solution does not de-colourise because bromine does not react with ethane due to absence of double bond.
(v) Sulphur burns around 300^oC. On reaction with oxygen present in air, it forms sulphur dioxide and small amount of sulphur trioxide.

$3\mathrm{S}+4{\mathrm{O}}_2\to {\mathrm{SO}}_2+2{\mathrm{SO}}_3$