Discussion Forum

1)

For one mole of a van der Waals' gas when b = 0 and T = 300 K, the pV vs. 1/V plot is shown below. The value of the van der Waals' constant a (atm L mol^-2)

Answer:

Option C

Explanation:

The van der Waals' equation of state is

$\left(p+\frac{n^{2}a}{V^{2}}\right)(V-nb)=RT$

for 1 mole and when b=0 so,

$\Rightarrow$    $pV=RT-\frac{a}{V}$ ..........(i)

Equation (i) is a straight equation between pV and $\frac{1}{V}$ whose slope is "-a'.

Equationg with slope of the straight line given in the graph 

   $-a=\frac{20.1-21.6}{3-2}=-1.5$

$\Rightarrow$ a=1.5