Question

What are the properties that change the values of a and b from the Van Der Waal's equation of state formula?

Answer 1

@Vocaloid @DuarteME @imqwerty

Answer 2

I know they are determined experimentally and given to students but what are the properties that impact the a and b values

Answer 3

The a term accounts for the non-elastic collisions and the b term accounts for the volume occupied by the particles

Answer 4

Vander Waal modified considered the intermolecular forces of attraction between the particles and the significant vol of the particles and modified the ideal gas equation

Answer 5

\(\Large{\left(P + \frac{an^2}{V^2} \right) \left(V - nb\right) = nRT}\)

P->observed pressure
n->moles
V->Volume of the \(container\)

he observed the intermolecular attraction forces b/w the particles and found out that it was smalled as compared to the ideal state pressure so he added the correction term \(\large{P' = \frac{an^2}{V^2}}\)

n/V -> number of collisions per until vol on wall
n/V -> no of particles per until vol

\(\large{P' \propto \frac{n}{V}.\frac{n}{V}}\)
\(\large{P' = a.\frac{n^2}{V^2}}\)

a-> Vander Waal const which represents extent of intermolecular interaction

Answer 6

He considered bi-molecular collisions while calculating the significant volume of the particles
V -nb -> free volume for the motion of the particles

nb is the correction term
b denotes the excluded volume or the co-volume or the effective volume that a \(N_A\) molecules take-up within a container of gas.





\(b = \Large{\frac{4}{3} \pi \left(2r\right)^3.N_A}\)

b depends on the radius or the volume occupied by the molecules

Answer 7

Thank you both for your timely responses!! I greatly appreciate the explanations as well!

Answer 8

Yw :-]