$X(aq.) + Na_2O_2 \to Y(aq.) \xrightarrow{BaCl_2} Z \downarrow_{\text{Insoluble in dil. } HCl}$
$X$ and $Y$ are different sodium salts. Then the anion present in the salt $(X)$ is:

Match the List-$I$ with List-$II$

List-$I$ $(\text{Redox Reaction})$	List-$II$ $(\text{Type of Redox Reaction})$
$A$. $CH_{4(g)} + 2O_{2(g)} \xrightarrow{\Delta} CO_{2(g)} + 2H_2O_{(l)}$	$I$. Disproportionation reaction
$B$. $2NaH_{(s)} \xrightarrow{\Delta} 2Na_{(s)} + H_{2(g)}$	$II$. Combination reaction
$C$. $V_2O_{5(s)} + 5Ca_{(s)} \xrightarrow{\Delta} 2V_{(s)} + 5CaO_{(s)}$	$III$. Decomposition reaction
$D$. $2H_2O_{2(aq)} \xrightarrow{\Delta} 2H_2O_{(l)} + O_{2(g)}$	$IV$. Displacement reaction

Choose the correct answer from the options given below:

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

Match the reactions in Column $I$ with the nature of the reactions/type of the products in Column $II$.

Column $I$	Column $II$
$A$. $O_2^{-} \rightarrow O_2 + O_2^{2-}$	$p$. redox reaction
$B$. $CrO_4^{2-} + H^{+} \rightarrow$	$q$. one of the products has trigonal planar structure
$C$. $MnO_4^{-} + NO_2^{-} + H^{+} \rightarrow$	$r$. dimeric bridged tetrahedral metal ion
$D$. $NO_3^{-} + H_2SO_4 + Fe^{2+} \rightarrow$	$s$. disproportionation

$PbO$ and $PbO_2$ react with $HCl$ according to the following chemical equations:
$(i)$ $2PbO + 4HCl \to 2PbCl_2 + 2H_2O$
$(ii)$ $PbO_2 + 4HCl \to PbCl_2 + Cl_2 + 2H_2O$
Why do these compounds differ in their reactivity?

Equivalent weight of $H_3PO_2$ when it disproportionates into $PH_3$ and $H_3PO_3$ is: