Answer: For question (a) HF would have the largest Van der Waal's constant a and for question (b) H2 would have the largest Van der Waal's constant b.
Explanation:
Since constant a,
F2 = 1.171, HF = 9.565 and H2 = 0.2453
And constant b,
H2 = 0.02651, HCl = 0.04061 and Cl2 = 0.05422
Therefore, highest constant a, is HF and highest constant b, is H2.