If the enthalpy of combustion of anhydrous oxalic acid is $x \, kcal \, mol^{-1}$,then how much heat in $kcal$ will be produced by the combustion of $2 \, g$ of oxalic acid?

Galena (an ore) is partially oxidized by passing air through it at high temperature. After some time,the passage of air is stopped,but the heating is continued in a closed furnace such that the contents undergo self-reduction. The weight (in $kg$) of $Pb$ produced per $kg$ of $O_2$ consumed is $. . . . .$ (Atomic weights in $g \ mol^{-1}: O = 16, S = 32, Pb = 207$)

$A$ 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? $(C=12 \ u; H=1 \ u)$

What will be the volume of $O_2$ gas at $STP$ which is obtained by thermal decomposition of $30.62 \ g$ $KClO_3$,with $80\%$ purity?

How many grams of dihydrogen are required to react with dinitrogen to produce $34 \ g$ of ammonia (in $g$)?

$A$ metal chloride contains $71\%$ chlorine by mass and has a vapor density of $50$. What is the atomic mass of the metal?