In which of the following reactions is no gas evolved on the product side? (Temperature is maintained below the boiling point of liquids formed)

Match the following columns:

Column - $A$	Column - $B$
$(A)$ $88 \ g$ of $CO_2$	$(1)$ $0.2 \ mol$
$(B)$ $6.022 \times 10^{23}$ molecules of water	$(2)$ $2 \ mol$
$(C)$ $5.6 \ L$ of $O_2$ at $STP$	$(3)$ $1 \ mol$
$(D)$ $96 \ g$ of $O_2$	$(4)$ $6.022 \times 10^{23}$ molecules
$(E)$ One mole of any gas at $STP$	$(5)$ $3 \ mol$

Iron sulphide is heated in air to form $A$,an oxide of sulphur. $A$ is dissolved in water to give an acid. The basicity of this acid is

Natural gas is a mixture of methane and ethane. The heat produced by the complete combustion of $10 \, L$ of this mixture at $S.T.P.$ is $476.6 \, kJ$. Given $\Delta H_{comb} (CH_4) = -894 \, kJ \, mol^{-1}$ and $\Delta H_{comb} (C_2H_6) = -1500 \, kJ \, mol^{-1}$,calculate the percentage of methane and ethane in the mixture by volume.

When $800 \ mL$ of $0.5 \ M$ nitric acid is heated in a beaker,its volume is reduced to half and $11.5 \ g$ of nitric acid is evaporated. The molarity of the remaining nitric acid solution is $x \times 10^{-2} \ M$. (Nearest Integer) (Molar mass of nitric acid is $63 \ g \ mol^{-1}$)

In a $20\%$ aqueous solution of $H_2O_2$,the mole fraction of water is $.......$.