One atmosphere is equal to

If some moles of $O_2$ diffuse in $18 \ sec$ and the same moles of another gas diffuse in $45 \ sec$,what is the molecular weight of the unknown gas?

Explain the following terms:
$(i)$ Isotherm
$(ii)$ Isochore
$(iii)$ Isobar

$A$ closed vessel contains an equal number of nitrogen and oxygen molecules at a pressure of $P \ mm$. If nitrogen is removed from the system,then the pressure will be

In a container,the mole ratio of two gases $A$ and $B$ is $2 : 5$. The total pressure of the container is $3.5 \times 10^5 \ Pa$. If all molecules of $A$ are removed from the container,what will be the pressure exerted by the molecules of $B$?

$A$ container consists of a mixture of four gases: $5 \text{ g } H_2$,$8 \text{ g } He$,$50 \text{ g } CO_2$,and $20 \text{ g } Ne$ at a certain temperature. Which of the following gases exerts the minimum partial pressure?