Q. $a\ and\ b$ are van der Waals’ constants for gases. Chlorine is more easily liquefied than ethane because
A) $a\ and\ b\ for\ {Cl}_{2} > a\ and\ b\ for\ C_{2}H_{6}$
B) $a\ and\ b\ for\ {Cl}_{2} < a\ and\ b\ for\ C_{2}H_{6}$
C) $a\ for\ {Cl}_{2} > a\ for\ C_{2}H_{6}\ but\ b\ for\ {Cl}_{2} > b\ for\ C_{2}H_{6}$
D) $a\ for\ {Cl}_{2} > a\ for\ C_{2}H_{6}\ but\ b\ for\ {Cl}_{2} < b\ for\ C_{2}H_{6}$
Explanation
(d)
van der Waals’ constant $a$ is due to force of attraction and $b$ due to finite size of molecules.
Thus greater the value of $a$ and smaller the value of $b,$ larger the liquefaction.
Thus, $a\left( {Cl}_{2} \right) > a\left( C_{2}H_{6} \right)\ and\ b\ \left( {Cl}_{2} \right) > b\ \left( C_{2}H_{6} \right)$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.