Question

In Van der Wall’s equation ( P + a/V2)( V – b ) = RT, Determine the dimensions of a and b.

Answer 1

Answer:

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

P is pressure, V is volume and T is temperature.

[P] = [F/A] = [MLT^−2/L^2] = [ML^−1T^−2]

[V] = [L^3]

We cannot add or subtract quantities of different dimensions. Therefore

[P] = [a/V^2] ⇒ [a] = [PV^2] = [ML^−1T^−2 L6] = [M L^5 T^−2]

∴ [a] = [M L^5 T^−2]

Similarly,

[b] = [V] = [L^3]