How many grams of zinc are required to produce $224 \ mL$ of hydrogen from dilute $H_2SO_4$ at $STP$?

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?

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 ......

If isobutane and $n$-butane are present in a gas,then how much oxygen should be required for the complete combustion of $5 \ kg$ of this gas?

The molar mass of $CaCO_{3}$ is $100 \ g/mol$. The maximum amount of carbon dioxide that can be liberated on heating $25 \ g$ of $CaCO_{3}$ is $.... \ g$.

The volume occupied by $4.4 \ g$ of $CO_2$ at $STP$ is ............... $L$.