One litre of a gas at $STP$ weighs $1.16 \ g$. It can possibly be:

$A$ mixture of dihydrogen and dioxygen at $1 \ bar$ pressure contains $20 \%$ by weight of dihydrogen. Calculate the partial pressure of dihydrogen. (in $bar$)

If the reduction of a sample of $Cu_2O$ yields $1.27 \, g$ of $Cu$,then how many grams of oxygen must be present in it?

An ideal gas mixture of $C_2H_6$ and $C_2H_4$ occupies a volume of $28 \ L$ at $1 \ atm$ and $273 \ K$. This mixture reacts completely with $128 \ g$ of $O_2$ to produce $CO_2$ and $H_2O_{(l)}$. What is the mole fraction of $C_2H_4$ in the mixture?

How many kilograms of $CaCO_3$ must be heated to obtain $56$ kilograms of $CaO$? [Atomic masses: $Ca = 40, C = 12, O = 16$]

What is the volume of $CO_2$ in liters produced at $STP$ by the complete decomposition of $9.85 \ g$ of $BaCO_3$? (Atomic mass of $Ba = 137$,$C = 12$,$O = 16$)