Question

Which of the following are correct statements :

• A. vander waals constant '$a$' is a measure of attractive force
• B. '$a$' is expressed in $atmL$${}^2$ mol${}^{-2}$
• C. '$b$' is expressed in $Lmol$${}^{-1}$
• D. vander waals constant '$b$' is also called co-volume or excluded volume

Answer 1

Answer: (A), (B), (C), (D)

(A) Vander waals constant '$a$' is a measure of attractive force
The van der waals constant '$a$' represents the magnitude of the attractive forces present between gas molecules. Higher is the value of '$a$', more easily the gas can be liquefied.
(B) Vander waals constant '$b$' is also called co-volume or excluded volume
The van der waals constant '$b$' represents the effective size of gas molecules. Higher is the value of '$b$', larger is the size and smaller is the compressible volume and more difficult it is to liquefy the gas.
(C) '$b$' is expressed in $Lmol$${}^{-1}$ The unit of b is same as the unit of molar volume.
(D) '$a$' is expressed in $atm$ $L^2$ $mo{l}^{-2}$
The unit of $a$ is equal to $\frac{pressure\times (volume{)}^2}{(Moles{)}^2}$