Select the correct statement(s):

  1. At Boyle's temperature a real gas behaves like an ideal gas at low pressure.
  2. Above critical conditions, a real gas behaves like an ideal gas.
  3. At high pressure van der Waals's constant 'b' dominates over 'a'.
  4. For Hydrogen gas 'b' dominates over 'a' at all temperatures.

Answer in textbook is given: 1 & 3

Can someone please explain me why 4 is not included in answer. My teacher told me that Due to very small size of hydrogen and helium atoms there value of "a" is negligible. So shouldn't "b" always dominate "a" for hydrogen and helium atoms ("a" and "b" are van der Waals' constants).

  • $\begingroup$ Hint: If A4 is true, H2 compressibility factor is always > 1. Analyze if it is true. $\endgroup$
    – Poutnik
    Aug 28, 2021 at 12:51


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