Methane has $T_{c} = 190 K$ and $P_{c} = 45.8 atm$ . Using the van der Waals relations and $R = 0.0821 L atm K^{- 1} mo l^{- 1}$ , the predicted critical volume $V_{c} = 3 b$ in $mL mo l^{- 1}$ (nearest integer) is

Numerical answer type, answer in mL/mol, tolerance 1.

Answer: 128 mL/mol

b = \frac{R T _{c}}{8 P _{c}} = \frac{0.0821 \times 190}{8 \times 45.8} = \frac{15.599}{366.4} = 0.04257 L mo l^{- 1}

V_{c} = 3 b = 0.1277 L mo l^{- 1} = 127.7 mL mo l^{- 1}

, i.e.

128 mL mo l^{- 1}

. The measured value (

99 mL mo l^{- 1}

) is smaller.