Explain the fire polishing of glass.

The rate of diffusion of methane at $1.0 \ atm$ pressure is twice that of another gas '$X$' kept at $1.45 \ atm$. The molecular weight of the gas '$X$' is
[$T$ kept constant]

At $298 \ K$, a flask '$A$' of unknown volume $(V)$ contains oxygen at $5 \ atm$. Another flask '$B$' of volume $2 \ L$ contains helium at $3 \ atm$. Two flasks are connected together by a small tube of zero volume. After the two gases are completely mixed, if the resulting mixture is found to have the mole fraction of oxygen as $0.2$, the volume of flask '$A$' (in $L$) is (Assume oxygen and helium as ideal gases)

Which one of the following is the kinetic energy of a gaseous mixture containing $3 \ g$ of hydrogen and $80 \ g$ of oxygen at temperature $T(K)$ (in $RT$)?

Which of the following statements is correct?

What happens when oil is added to water? Why?