The gaseous state is characterized by which of the following properties?

Mountaineers carry oxygen cylinders with them because ...

$50 \ mL$ of hydrogen diffuses out through a small hole from a vessel in $20 \ min$. The time needed for $40 \ mL$ of oxygen to diffuse out is ............. $min$.

The ratio of rates of diffusion of oxygen and an unknown gas is $1:4$. The unknown gas is

Gas $A$ diffuses $6$ times faster than hydrogen gas. What is the molar mass of $A$?

At $27^{\circ} C$, a closed vessel contains a mixture of equal weights of helium (mol. wt. = $4$), methane (mol. wt. = $16$) and sulphur dioxide (mol. wt. = $64$). The pressure exerted by the mixture is $210 \ mm$. If the partial pressures of helium, methane and sulphur dioxide are $p_1, p_2$ and $p_3$ respectively, which one of the following is correct?