Question

The ratio a/b (the terms used in van der Waal's equation) has the unit :

• A. Atm litre $mo{l}^{-1}$
• B. Atm $d{m}^{3}mo{l}^{-1}$
• C. Dyne cm $mo{l}^{-1}$
• D. all of these

Answer 1

The correct option is D all of these

From van der Waal,s equation
$[P+\frac{a}{V^2}][V-b]=nRT$
units of 'a' - 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 ration a/b is
atm.lit/mol = Atm $d{m}^3$/mol = Dyne cm/mol