JEE Main 2010 — Inorganic Chemistry

Which one of the following has an optical isomer ? (en = ethylenediamine)

A solution containing $2.675 \mathrm{~g}$ of $\mathrm{CoCl}_3 .6 \mathrm{NH}_3$ (molar mass $=267.5 \mathrm{~g} \mathrm{~mol}^{-1}$ ) is passed through a cation exchanger. The chloride ions obtained in solution were treated with excess of $\mathrm{AgNO}_3$ to give $4.78 \mathrm{~g}$ of $\mathrm{AgCl}$ (molar mass $=143.5 \mathrm{~g} \mathrm{~mol}^{-1}$ ). The formula of the complex is (At. Mass of $\mathrm{Ag}=108 \mathrm{u}$ )

Three reactions involving $\mathrm{H}_2 \mathrm{PO}_4^{-}$are given below : (i) $\mathrm{H}_3 \mathrm{PO}_4+\mathrm{H}_2 \mathrm{O} \rightarrow \mathrm{H}_3 \mathrm{O}^{+}+\mathrm{H}_2 \mathrm{PO}_4^{-}$ (ii) $\mathrm{H}_2 \mathrm{PO}_4^{-}+\mathrm{H}_2 \mathrm{O} \rightarrow \mathrm{HPO}_4^{2-}+\mathrm{H}_3 \mathrm{O}^{+}$ (iii) $\mathrm{H}_2 \mathrm{PO}_4^{-}+\mathrm{OH}^{-} \rightarrow \mathrm{H}_3 \mathrm{PO}_4+\mathrm{O}^{2-}$ In which of the above does $\mathrm{H}_2 \mathrm{PO}_4^{-}$act as an acid ?