Write one chemical equation each for the chemical reaction in which the following have taken place: (i) Change in colour (ii) Change in temperature…

(i) Change in colour: The solution will become green in colour. \[\mathrm{Fe}(\mathrm{~s})+\mathrm{CuSO}_{4}(\mathrm{aq}) \rightarrow \mathrm{FeSO}_{4}+\mathrm{Cu}(\mathrm{~s}) \] Blue Green

(ii) Change in temperature: The temperature will increase. \(\displaystyle \mathrm{NaOH}(\mathrm{aq})+\mathrm{HCl}(\mathrm{aq}) \rightarrow \mathrm{NaCl}(\mathrm{aq})+\mathrm{H}_{2} \mathrm{O}(\mathrm{l})+\) Heat

(iii) Formation of precipitate: Yellow precipitate of \(\displaystyle \mathrm{PbI}_{2}\) is formed. \[\mathrm{Pb}\left(\mathrm{NO}_{3}\right)_{2}(\mathrm{aq})+2 \mathrm{KI}(\mathrm{aq}) \rightarrow \underset{\text { Yellow }}{\mathrm{PbI}_{2}(\mathrm{~s})}+2 \mathrm{KNO}_{3}(\mathrm{aq}) \]