Which of the following has higher surface tension: pure water or soapy water?

$A$ $4 : 1$ molar mixture of $He$ and $CH_4$ is kept in a vessel at $20 \ bar$ pressure. Due to a hole in the vessel,the gas mixture leaks out. What is the composition of the mixture effusing out initially?

What is the temperature at which the kinetic energy of $0.3 \text{ moles}$ of helium is equal to the kinetic energy of $0.4 \text{ moles}$ of argon at $400 \text{ K}$ (in $\text{ K}$)?

At the same temperature and pressure,the rate of diffusion of helium with respect to methane is ...... .

Which of the following gas mixtures is not applicable for Dalton's law of partial pressure?

Mixing of two different ideal gases under isothermal reversible conditions will lead to: