Which of the following compounds does not have similarity in their structural aspect?

Air contains $23\% \, O_2$ and $77\% \, N_2$ by weight. What is the percentage of $O_2$ by volume?

$A$ mixture of sodium oxide $(Na_2O)$ and calcium oxide $(CaO)$ is dissolved in water and saturated with excess carbon dioxide $(CO_2)$ gas. The resulting solution is $......$ It contains $.........$ :

Mole fraction of $O_2$ in an $O_2$ and $O_3$ mixture is $0.25$. Hence,the percentage concentration $\left( \frac{w}{W}\% \right)$ of $O_2$ in the mixture is:

Which one of the following is the lightest?

Match List-$I$ with List-$II$.

List-$I$	List-$II$
$A$. $16 \ g \ CH_{4(g)}$	$I$. Weighs $28 \ g$
$B$. $1 \ g \ H_{2(g)}$	$II$. $60.2 \times 10^{23}$ electrons
$C$. $1 \ mole \ N_{2(g)}$	$III$. Weighs $32 \ g$
$D$. $0.5 \ mol \ SO_{2(g)}$	$IV$. Occupies $11.2 \ L$ volume at $STP$

Choose the correct answer from the options given below: