Which one of the following is the correct PV vs P plot at constant temperature for an ideal gas? (P and V stand for pressure and volume of the gas respectively)

The unit of the van der Waals gas equation parameter 'a' in $$\left( {P + {{a{n^2}} \over {{V^2}}}} \right)(V - nb) = nRT$$ is :

The interaction energy of London forces between two particles is proportional to r^x, where r is the distance between the particles. The value of x is :

A mixture of one mole each of H₂ , He and O₂ each are enclosed in a cylinder of volume V at temperature T. If the partial pressure of H₂ is 2 atm, the total pressure of the gases in the cylinder is :