Light green crystals of ferrous sulphate lose water molecules and turn brown on exposure to air. This is due to its oxidation to:

Which of the following are non-metal displacement reactions?
$(A)$ $Ca_{(s)} + 2 H_2 O_{(l)} \longrightarrow Ca(OH)_{2(aq)} + H_{2(g)}$
$(B)$ $V_2 O_{5(s)} + 5 Ca_{(s)} \stackrel{\Delta}{\longrightarrow} 2 V_{(s)} + 5 CaO_{(s)}$
$(C)$ $2 Fe_{(s)} + 3 H_2 O_{(g)} \stackrel{\Delta}{\longrightarrow} Fe_2 O_{3(s)} + 3 H_{2(g)}$
$(D)$ $Cr_2 O_{3(s)} + 2 Al_{(s)} \stackrel{\Delta}{\longrightarrow} Al_2 O_{3(s)} + 2 Cr_{(s)}$

When copper is added to concentrated $H_2SO_4$,$CuSO_4$ is produced along with another sulphur-containing compound $X$. The compound $X$ is

What are $X$ and $Y$ in the following reactions?
$(i) \ MnO_4^{-} + I^{-} \xrightarrow{H^{+}} X$
$(ii) \ MnO_4^{-} + I^{-} \xrightarrow{H_2O} Y$

$AgCl$ when heated with $Na_2CO_3$ gives:

In neutral or faintly alkaline medium,$MnO_4^{-}$ oxidizes $I^{-}$ to iodate. What is the volume (in $L$) of $0.02 \ M \ KMnO_4$ required to completely convert $1 \ L$ of $0.5 \ M \ KI$ solution to iodate in neutral or faintly alkaline medium?