Equal masses of helium and oxygen are mixed in an empty container at $25^{\circ} \mathrm{C}$. What is the fraction of the total pressure exerted by helium?

What is the number of oxygen atoms bonded to chlorine in its strongest oxoacid?

Dissociation constant of 0.01 M weak acid is $10^{-4}$. What is percent dissociation of acid?

Which among the following gases is least adsorbed on solid at similar conditions of temperature and pressure?