Carbon dioxide has $T_{c} = 304 K$ and $P_{c} = 72.8 atm$ . From the van der Waals relations with $R = 0.0821 L atm K^{- 1} mo l^{- 1}$ , the value of $a$ in $L^{2} atm mo l^{- 2}$ (two decimals) is

Numerical answer type, answer in L^2 atm/mol^2, tolerance 0.03.

Answer: 3.61 L^2 atm/mol^2

From

T_{c} = 8 a /27 R b

and

P_{c} = a /27 b^{2}

, eliminating

b

gives

a = \frac{27 R ^{2} T _{c}^{2}}{64 P _{c}} = \frac{27 \times ( 0.0821 ) ^{2} \times ( 304 ) ^{2}}{64 \times 72.8} = \frac{16818.89}{4659.2} = 3.610

, i.e.

3.61 L^{2} atm mo l^{- 2}