What is the volume in $dm^3$ occupied by $3 \ mol$ of ammonia gas at $STP$?

To neutralize $10 \, mL$ of $M/5$ $NaOH$,the volume of $M/20$ $HCl$ required is......$mL$.

When ${CO_2}_{(g)}$ is passed over hot coke,it is reduced to ${CO}_{(g)}$. When $0.5 \, L$ of ${CO_2}_{(g)}$ is passed over hot coke,the total volume of the gas increases by $700 \, mL$ at $STP$. The composition of the resulting gaseous mixture is:

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

At $STP$,$4.4 \ g$ of an unknown gas occupies a volume of $2.24 \ L$. What is the gas?

$25 \ mL$ of a solution of $Na_2CO_3$ having a specific gravity of $1.25$ required $32.9 \ mL$ of a solution of $HCl$ containing $109.5 \ g$ of the acid per litre for complete neutralization. Calculate the volume of $0.84 \ N$ $H_2SO_4$ that will be completely neutralized by $125 \ g$ of the $Na_2CO_3$ solution (in $mL$).