What is the percentage of lead in a lead pencil (in $\%$)?

$0.45 \ g$ of an organic compound on combustion gives $0.792 \ g$ of $CO_2$ and $0.324 \ g$ of $H_2O$. In the Kjeldahl method,$0.24 \ g$ of the same compound yields ammonia,which is absorbed in $50 \ mL$ of $0.25 \ N \ H_2SO_4$. The excess acid requires $77.0 \ mL$ of $0.25 \ N \ NaOH$ for neutralization. Determine the empirical formula of the compound. (Atomic masses: $C = 12, H = 1, O = 16, N = 14, S = 32$)

Which is the correct option for $0.1 \ M$,$500 \ mL$ of $AgCl$?

Which one of the following is the lightest?

Match the following:

Column-$I$	Column-$II$
$A$. $5.6 \ L$ of $SO_{2(g)}$ at $STP$	$I$. $32 \ g$
$B$. $1.2 \times 10^{24}$ atoms of oxygen	$II$. $66 \ g$
$C$. $33.6 \ L$ of $CO_{2(g)}$ at $STP$	$III$. $42 \ g$
$D$. $1.5 \ g$-molecule of $N_2$	$IV$. $16 \ g$

The correct match is:

$A$ gas has a density of $2.68 \ g/L$ at $STP$. Identify the gas.