Question

Van der waals constant "b" of helium is $24mLmo{l}^{-1}$. Find molecular diameter of helium.

• A.
• B.
• C.
• D.

Answer 1

The correct option is C

b = 4 $\times$ volume occupied by molecules of 1 mole of a gas ,

or b = $4N_A⟮\frac{4}{3}\pi r^3⟯$

or r = $⟮\frac{3b}{16N_A\pi }⟯$

= $⟮\frac{3\times 24}{16\times 6.023\times {10}^{23}\times 3.14}{⟯}^{\frac{1}{3}}cm$

= 1.355 $\times {10}^{-8}$ cm.