Question

The ratio $\frac{a}{b}$ (the terms used in van der Waal's equation) has the unit:

• A. $atmlitremo{l}^{-1}$
• B. $atmd{m}^{3}mo{l}^{-1}$
• C. $dynecmmo{l}^{-1}$
• D. all of the above

Answer 1

Answer: (D)

all of the above

From Vander Waals equation, $[P+\frac{a}{V^2}][V-b]=nRT$

Units of '$a$' are : $atm$ $litr{e}^{2}mo{l}^{-2}$$=atmd{m}^{6}mo{l}^{-2}=dynec{m}^{4}mo{l}^{-2}$

The units of '$b$' are: $litre$ $mo{l}^{-1}=d{m}^{3}mo{l}^{-1}=c{m}^{3}mo{l}^{-1}$

So, their ratio $\frac{a}{b}$ is $atmlit/mol=atmd{m}^3/mol=dynecm/mol$

Hence, the correct answer is option $\text{D}$.