Question

Using van der Waals equation, calculate the constant $a$ when 2 mol of a gas confined in a 4 L flask exerts a pressure of 11.0 atm at a temperature of 300 K. The value of $b$ is $0.05$ L mol${}^{-1}$.

[Write your answer to the nearest integer]

Answer 1

The van der Waals equation of state for a gas is

$[P+\frac{a{n}^2}{V^2}](V-nb)=nRT$

$\therefore [11+\frac{a\times 2^2}{4^2}](4-2\times 0.05)=2\times 0.0821\times 300$

or $a=6.46\approx 6$ atm L${}^2$ mol${}^{-2}$