# Calculate molecular diameter of He from its Vander Waal's constant b = 24mL$mol^{-1}$

$(a)\;271 \overset{\circ}{A}\qquad(b)\;282 \overset{\circ}{A}\qquad(c)\;2.71 \overset{\circ}{A}\qquad(d)\;0.27 \overset{\circ}{A}$

b = $4\times$ Volume occupied by the molecules in one mole of gas.
$= 4\times N\times(\large\frac{4}{3}\pi r^3)$
$r = [\large\frac{3\times24}{16\times(\large\frac{22}{7})\times6.023\times10^{23}}]$
$=1.355\times10^{-8}$cm
$d = 2\times r$
$= 2\times1.355\times10^{-8}$cm
$=2.71\overset{\circ}{A}$