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Methane has compressibility factor value of 0.9 at reduced pressure of 1.0 and reduced temperature of 1.5. For propane, the critical temperature and pressure are 369.8 K and 42.48 bar, respectively. Take R = 8.314 kJ/kmol.K. Applying the principle of corresponding states, the molar volume of propane (in m3/kmol) at the same reduced pressure and temperature is

  • A.0.355
  • B.0.526
  • C.0.791
  • D.0.977

Answer: D

The molar volume of propane is 0.977 m3/kmol.

By the principle of corresponding states, gases at the same reduced pressure and temperature have the same compressibility factor, so propane also has Z = 0.9. Its actual conditions are

\[ \begin{aligned} T &= 1.5 \times 369.8 = 554.7\ \text{K} \\ P &= 1.0 \times 42.48\ \text{bar} = 4248\ \text{kPa} \end{aligned} \]

\[ \begin{aligned} \bar{v} &= \frac{ZRT}{P} = \frac{0.9 \times 8.314 \times 554.7}{4248} \\ &= 0.977\ \text{m}^{3}\text{/kmol} \end{aligned} \]

Treating propane as an ideal gas (Z = 1) would give 1.086, and 0.355, 0.526 and 0.791 do not follow from Z = 0.9 at these conditions.

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