Question

Using van der Waal's equation, calculate the constant $a$ when 2 moles 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 $0.05Lmo{l}^{-1}$.(as nearest integer)

Answer 1

The van der Waal's equation of state for a gas is
$[P+\frac{a{n}^2}{V^2}](V-nb)=nRT$
$\therefore [11+\frac{a\times 2^2}{4^2}](4-2\times 0.05)=2\times 0.0821\times 300$
$a=6.46atm{L}^{2}mo{l}^{-2}$
So, nearest integer value is 6.