JEE Advance - Chemistry (2008 - Paper 1 Offline - No. 11)
Explanation
Van der Waals equation is $$\left( {P + {{a{n^2}} \over {{V^2}}}} \right)(V - nb) = nRT$$, where a is a constant whose value depends on the attraction between the gas molecules and b is the volume that is occupied by one mole of gas.
In option (A), it behaves similar to an ideal gas in the limit of large molar volumes. When the volume is very large then the attraction between the gas molecules can be neglected, so a $$\approx$$ 0 and the volume occupied by one mole of gas compared to large volume of container will also be neglected. So, b $$\approx$$ 0. Now, we can neglect a and b and the gas behaves ideally. Thus, option A is correct.
In option (B), it behaves similar to an ideal gas in limit of low pressure and high temperatures. Now, the pressure is very low. So, the attraction between the particles is negligible.
Van der Waals coefficients that are dependent on the identity of the gas but are independent of the temperature. Van der Waals coefficient depends on the attraction between the gas molecules (each of which is characteristic of a gas) and b is the volume that is occupied by one mole of the molecules. So, this option is correct. Since, molecules of Van der Waals gas exert force of attraction on each other; hence, the force which they exert on the walls of the container is less than the force exerted by it if the gas would have been ideal.
Thus, option (D) is correct.
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