vander walls equation and critical phenomenon

For a gas obeying the van der Waals' equation, at the critical point

Demonstrate that Eqs. (2. 6a) and (2 . 6b) are valid for a substance, obeying the Van der Qaals equation, in critical state Make use of the fact that the critical state corresponds to the point of inflection in the isothermal curve p (V) .

In vander waal's equation of the gas law the constant of a is a measure of

Find volume of 2 moles of a vander waals gas at critical pressure & critical temperature. Given for gas : [P_(C)=2atm and T_(C)=300K]

Which of following statements (s) is true I -Slope of isotherm at critical point is maximum. II-Larger is the value of T_(c) easler is the liquification of gas. III-Vander waals equation of state is applicable below critical temperature at all pressure.