For the combustion reaction of $1 \ mol$ of benzene,if all reactants and products are in the gaseous state,then $\Delta n_{(g)}$ is equal to ......

$A$ hydrocarbon containing $C$ and $H$ has $92.3 \% C$. When $39 \ g$ of hydrocarbon was completely burnt in $O_2$,$x$ moles of water and $y$ moles of $CO_2$ were formed. $x$ moles of water is sufficient to liberate $0.75$ moles of $H_2$ with $Na$ metal. What is the weight (in $g$) of oxygen consumed? $(C=12 \ u; H=1 \ u)$

$A$ gas weighing $2.4 \ g$ has a vapor density of $11.2$. What is its volume in $L$ at $STP$?

$20 \, mL$ of a $1 \, N$ solution of $KMnO_4$ just reacts with $20 \, mL$ of a solution of oxalic acid. The weight of oxalic acid crystals in $1 \, L$ of the solution is $... \, g$

Calcium carbonate reacts with aqueous $HCl$ to give $CaCl_{2}$ and $CO_{2}$ according to the reaction,
$CaCO_{3(s)} + 2HCl_{(aq)} \rightarrow CaCl_{2(aq)} + CO_{2(g)} + H_{2}O_{(l)}$
What mass of $CaCO_{3}$ is required to react completely with $25 \ mL$ of $0.75 \ M$ $HCl$ (in $g$)?

When a $1.0 \, g$ mixture of $NaHCO_3$ and $Na_2CO_3$ is heated at $150^{\circ}C$,$112.0 \, mL$ of $CO_2$ is produced at $STP$. Calculate the percentage of $Na_2CO_3$ in the mixture. $(Na = 23, C = 12, O = 16)$