What happens when: (a) An iron nail is dipped in copper (II) sulphate solution? (b) Potassium iodide solution is mixed with lead nitrate solution?…

(a) Blue colour of copper sulphate solution changes to pale green \[\mathrm{Fe}(\mathrm{~s})+\mathrm{CuSO}_{4}(\mathrm{aq}) \rightarrow \mathrm{FeSO}_{4}(\mathrm{aq})+\mathrm{Cu}(\mathrm{~s}) \]

(b) Yellow precipitate is formed. \[\mathrm{Pb}\left(\mathrm{NO}_{3}\right)_{2}(\mathrm{aq})+2 \mathrm{KI}(\mathrm{aq}) \rightarrow \mathrm{PbI}_{2}(\mathrm{~s})+2 \mathrm{KNO}_{3}(\mathrm{aq}) \]

(c) White colour of silver chloride changes to grey. \[2 \mathrm{AgCl} \xrightarrow{\text { sunlight }} 2 \mathrm{Ag}+\mathrm{Cl}_{2} \]