Question

12. For one mole of a van der Waal's gas when b = 0
and T = 300 K, the PV vs. 1N plot is shown below.
The value of the van der Waal's constant 'a' (atm.
litre2 mol-2) is
[Graph not to scale]
PV (litre-atm mol)
2.0 3.0
1 (mol litre")
(2) 4.5
(4) 3.0
(1) 1.0
(3) 1.5

Answer 1

Answer:

Van der waals equation for 1 mole of real gas:

(P+a/v^2)(v-b) =RT

Given that, b=0

So, the equation becomes;

(P+a/v^2)v =RT

or

pv + a/v = RT

or

pv = -ax1/v +RT

Comparing with equation of straight line: y = mx +c, it can be concluded that

pv vs 1/v graph would be a straight line with a negative slope equal to a.

Thus, slope of the plot = a = (y2-y1)/(x2-x1) = (21.6-20.1)/(3-2) =1.5.