Question

Calculate the radius of $He$ atoms if its Vander Waal's constant ${}^{\prime }{b}^{\prime }$ is $24$ mL mol${}^{-1}$.

[Note 1 mL = 1 cubic centimeter]

• A. $1.355\stackrel{\circ }{A}$
• B. $1.314\stackrel{\circ }{A}$
• C. $1.255\stackrel{\circ }{A}$
• D. $0.355\stackrel{\circ }{A}$

Answer 1

The correct option is A $1.355\stackrel{\circ }{A}$

$b=4\times N\times \left(\frac{4}{3}\pi r^3\right)$

The volume occupied by the molecules in one mole of gas.

$=4\times N\times \left(\frac{4}{3}\pi r^3\right)$

$r=3\times \frac{24}{16}\times \left(\frac{7}{22}\right)\times 6.023\times {10}^{23}$

$=1.355\times {10}^{-10}$

Hence, the correct option is $\text{A}$