One litre oxygen gas at $STP$ will weigh $.................. \ g$

$A$ gaseous mixture contains $50\%$ Helium and $50\%$ Methane by volume. What is the percentage of Methane by weight in the mixture?

Volume of air required to completely burn $10 \ L$ of $C_2H_4$ is ................ $L$ (assume all volumes are measured at the same temperature and pressure,and air contains $20\%$ oxygen by volume).

The volume of $0.1 \ M \ HCl$ required in $mL$ to neutralise $20 \ mL$ of a solution containing $0.106 \ g$ of $Na_2CO_3$ is

What is the ratio of the active masses of $22 \ g$ $CO_2$,$3 \ g$ $H_2$,and $7 \ g$ $N_2$ in a gaseous mixture?

The mass of $BaCO_3$ produced when excess $CO_2$ is bubbled through a solution of $0.205 \ mol$ $Ba(OH)_2$ is ............ $g$.