Q4(b)(ii). van der Waals constants of NO and CCl₄; nearness to ideal behaviour
The critical temperature and pressure for NO gas are 177 K and 64 atm, respectively, and for CCl₄, they are 550 K and 45 atm, respectively. Which gas has the smaller values of the van der Waals' constants, a and b? Which is the most nearly ideal in behaviour at 300 K and 10 atm?
Answer in brief
NO has the smaller a (1.39 against 19.1 L² atm mol⁻²) and smaller b (0.0284 against 0.125 L mol⁻¹), and it is the most nearly ideal at 300 K and 10 atm (Z = 0.989), while CCl₄ is a liquid.
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Coversvan der Waals constantscritical constantscompression factorreduced temperaturelaw of corresponding states
All parts of Question 4
- 4(a) E.m.f. of a hydrogen–copper cell at 25 °C10 marks
- 4(b)(i) Thermal conductivity of the gas in an ageing foam10 marks
- 4(b)(ii) van der Waals constants of NO and CCl₄; nearness to ideal behaviour10 marks
- 4(c) Phenol–water system and the importance of tie lines20 marks