Under the same conditions of pressure and temperature,the same volume of two gases $A$ and $B$ diffuse through a porous partition in $20 \ s$ and $10 \ s$ respectively. The molecular mass of $A$ is $49 \ u$. The molecular mass of $B$ will be ............. $u$.

The rate of diffusion of $SO_3$,$CO_2$,$PCl_3$ and $SO_2$ gases are in the following order:

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?

The unit of pressure is equivalent to which of the following?

Which of the following is true for the gaseous state?

What are the measurable properties of a gas?