What volume does a gas occupy at $STP$?

Equal volume of $2$ gases $A$ and $B$ diffuse in $20 \ s$ and $10 \ s$ respectively. If molar mass of $A$ is $80$,then the molar mass of $B$ is:

What is the ratio of the rates of diffusion of gases $A$ and $B$ having molecular weights $36$ and $64$ respectively?

$A$ bulb contains $1 \ g$ of $H_2$ and $1 \ g$ of $He$. If the total pressure is $1.2 \times 10^3 \ Pa$,then the partial pressure of $He$ is ............. $Pa$.

The rate of diffusion of two gases $x$ and $y$ is $10 \, mL/s$ and $40 \, mL/s$ respectively,then the ratio of their molar masses $(Mw_x : Mw_y)$ is

$A$ mixture of hydrogen and oxygen contains $40 \%$ hydrogen by mass when the total pressure is $2.2 \, bar$. The partial pressure of hydrogen is $bar$. (Nearest Integer)