1. The problem statement, all variables and given/known data Calculate the molecular diameter of hydrogen, assuming the spherical shape on the basis of van der Waals coefficients. Van der Waals Coefficients for hydrogen a = 0.244 atm L2.mol-2 b*103 = 26.6 L.mol-1 2. Relevant equations Not indicated in the problem but I would think the Van der Waals equation of state. 3. The attempt at a solution For hydrogen: Since the constant b is an indication of molecular volume, it could be used to estimate the radius of an atom or molecule, modeled as a sphere. This leads to the following estimate of radius: V = b/N = (26.6 x 10-6)/6.02*1023 (I have first converted b unit to m3/mol) V = 4πr3/3 which gives r = 0.219nm corresponding to a molecular diameter D = 0.438nm I would like to know if my reasoning is correct; especially the equation V = b/N I'm also confused about the inclusion of the a constant in the problem when it isn't needed as far as I know.