If combustion of $4 \ g$ of $CH_4$ liberates $2.5 \ kcal$ of heat,the heat of combustion of $CH_4$ is ..... $kcal/mol$.

$A$ cylinder contains a mixture of $5 \ g$ of $N_2$ and $6 \ g$ of $Ar$ gases. If the total pressure of the mixture of the gases in the cylinder is $30 \ bar$,then the partial pressure of $N_2$ gas is (in $bar$)

What is the weight of carbon in $kg$ required to produce $270 \ kg$ of aluminum from bauxite by the Hall-Heroult process?

Calculate the approximate mass (in $g$) of $H_2S$ required for the following reaction when $15 \ L$ of oxygen at $STP$ reacts completely.
$2 H_2S_{(g)} + 3 O_{2(g)} \longrightarrow 2 SO_{2(g)} + 2 H_2O_{(g)}$
(molar mass of $H_2S = 34 \ g \ mol^{-1}$)

What is the value of percent atom economy when an organic compound of formula weight $75 \ u$ is obtained from reactants having sum formula weight $225 \ u$?

How many grams of ethanol are required in the reaction with $Na$ metal to produce $560 \ mL$ of dihydrogen gas at $STP$? (Molecular mass of ethanol = $46 \ g \ mol^{-1}$)