Question

Select the correct statements about van der Waals' constant ${}^{\prime }{b}^{\prime }$
1. It is excluded volume ​
2. ​​​​​​Its unit is ${\text{mol L}}^{-1}$
3. It depends on intermolecular force
4. ​​​​​​​Its value depends on molecular size

• A. 2,3
• B. 1,4
• C. 2,3,4
• D. 3,4

Answer 1

The correct option is B 1,4

$(P+\frac{a{n}^2}{V^2})(V-nb)=nRT$
Since volume of gas molecule is significant for real gases so the nb term is the correction in volume here for real gases. Free volume for n moles of gas is $(V-nb)$ where $nb$ is the excluded volume for $n$ moles of gas because of its significant molecular size. So excluded volume for one mole of gas is $b$.
From the above equation unit of $b={\text{L mol}}^{-1}$.
'b' is the measure of effective size of gas molecule.
Hence, the correct answer is option (b).