CGPET 2021 Solved Paper

Lead $(\mathrm{Pb}^{2+})$, zinc $(\mathrm{Zn}^{2+})$, silver $(\mathrm{Ag}^{+})$can be precipitated by $\mathrm{HCl}$ and $\mathrm{H}_2 \mathrm{S}$. Hence, answer will be none of the above. (a) Lead cation react with hydrochloric acid to give white ppt. of lead chloride. $\mathrm{Pb}^{2+} + \mathrm{HCl} \rightarrow \underset{\text{(White ppt.) Lead chloride}}{\mathrm{PbCl}_2} \downarrow$ Lead cation reacts with hydrogen sulphide to form insoluble ppt. of lead sulphide. $\mathrm{Pb}^{2+} + \mathrm{H}_2\mathrm{S} \rightarrow \underset{\text{Lead sulphide}}{\mathrm{PbS}} \downarrow$ (b) Zinc cation react with $\mathrm{HCl}$ to give white ppt. of zinc chloride. $\mathrm{Zn}^{2+} + \mathrm{HCl} \rightarrow \underset{\text{Zinc chloride}}{\mathrm{ZnCl}_2}\downarrow$ Zinc cation reacts with $\mathrm{H}_2\mathrm{S}$ to give yellowish ppt. of zinc sulphide. $\mathrm{Zn}^{2+} + \mathrm{H}_2\mathrm{S} \rightarrow \underset{\text{Zinc sulphide}}{\mathrm{ZnS}} \downarrow$ (c) Silver cation reacts with hydrochloric acid to give white ppt. of $\mathrm{AgCl}$ (silver chloride). $\mathrm{Ag}^{+} + \mathrm{HCl} \rightarrow \underset{\text{(White ppt.) Silver chloride}}{\mathrm{AgCl}}\downarrow$ Silver cation react with hydrogen sulphide to form black colour ppt. of $\mathrm{Ag}_2\mathrm{S}$ (silver sulphide). $\mathrm{Ag}^{+} + \mathrm{H}_2\mathrm{S} \rightarrow \underset{\text{Silver sulphide}}{\mathrm{Ag}_2\mathrm{S}}\downarrow$