Sea divers use a mixture of

Match Column-$I$ with Column-$II$ for the given properties/applications mentioned therein.

Column-$I$	Column-$II$
$A$. $H$	$1$. Used in the name of perhydrol.
$B$. $H_2$	$2$. Can be reduced to dihydrogen by $NaH$.
$C$. $H_2O$	$3$. Can be used in hydroformylation of olefin.
$D$. $H_2O_2$	$4$. Can be used in cutting and welding.

Correlate the items listed in Column $I$ with those listed in Column $II$. Find out as many correlations as you can.

Column $I$	Column $II$
$A$. Synthesis gas	$1$. $Na_2[Na_4(PO_3)_6]$
$B$. Dihydrogen	$2$. Oxidising agent
$C$. Heavy water	$3$. Softening of water
$D$. Calgon	$4$. Reducing agent
$E$. Hydrogen peroxide	$5$. Stoichiometric compounds of $s-$block elements
$F$. Salt like hydrides	$6$. Prolonged electrolysis of water
	$7$. $Zn + NaOH$
	$8$. $Zn + dil. H_2SO_4$
	$9$. Synthesis of methanol
	$10$. Mixture of $CO$ and $H_2$

Match the correct option from Column $-A$ and Column $-B.$

Column $-A$	Column $-B$
$(1).$ $H_2O_2$	$(p).$ As moderator
$(2).$ $D_2O$	$(q).$ As fuel
$(3).$ Liquid $H_2$	$(r).$ For to make hard water soft
$(4).$ Zeolite	$(s).$ As disinfectant

Match the following columns:

Column-$I$	Column-$II$
$(i)$ Hydrogen peroxide	$(a)$ Used as air purifier in submarines
$(ii)$ Calcium sulphate hemihydrate	$(b)$ Used for water softening
$(iii)$ Potassium superoxide	$(c)$ Antiseptic
$(iv)$ Calgon	$(d)$ Plaster of Paris

Oxalic acid reacts with concentrated $H_2SO_4$ to produce a mixture of two gases. When this mixture is passed through caustic potash,one of the gases is absorbed. Which substance is formed by the absorption of the gas in caustic potash?