States of Matter 1 Question 45
45. A gas described by van der Waals’ equation
(2008, 4M)
(a) behaves similar to an ideal gas in the limit of large molar volumes
(b) behaves similar to an ideal gas in the limit of large pressures
(c) is characterised by van der Waals’ coefficients that are dependent on the identity of the gas but are independent of the temperature
(d) has the pressure that is lower than the pressure exerted by the same gas behaving ideally
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Solution:
- Option (a) is correct because in the limit of large volume, both intermolecular force and molecular volume becomes negligible in comparison to volume of gas.
Option (b) is wrong statement because in the limit of large pressure $Z>1$.
Option (c) is correct statement. For a van der Waals’ gas, van der Waals’ constants $a$ and $b$ are characteristic of a gas, independent of temperature.
Option (d) is wrong statement because $Z$ can be either less or greater than unity, hence real pressure can be less or greater than ideal pressure.
