Question

Which statement best describes the density and rate of effusion of the following gases?

$N{O}_2$ , $C_2{H}_8$, $Kr$ , $Xe$, $F_2$

• A. Fluorine has the lowest density and the lowest rate of effusion
• B. Xenon has the greatest rate of effusion and the lowest density
• C. Krypton has the lowest density and the greatest rate of effusion
• D. Ethane has the greatest rate of effusion and the lowest density
• E. Nitrogen dioxide has the highest density and the greatest rate of effusion

Answer 1

The correct option is D Ethane has the greatest rate of effusion and the lowest density

Ethane has the greatest rate of effusion and the lowest density
The rate of effusion is inversely proportional to the square root of molar mass. The gas with lowest molar mass has the greatest rate of effusion.
$PM=\rho RT$
Thus, the density of a gas is directly proportional to its molar mass. A gas with lowest molar mass will have lowest density.