The rate of effusion of a gas is directly proportional to.....

Which of the following statements is incorrect?

$40 \ mL$ of hydrogen diffuses through a fine hole in $25 \ min$. How much time (in $min$) will $20 \ mL$ of oxygen take to diffuse under the same conditions?

The densities of hydrogen and oxygen are $0.09 \ g \ L^{-1}$ and $1.44 \ g \ L^{-1}$ respectively. If the rate of diffusion of hydrogen is $1$,then the rate of diffusion of oxygen in the same units will be:

At $27^{\circ} C$, a closed vessel contains a mixture of equal weights of helium (mol. wt. = $4$), methane (mol. wt. = $16$) and sulphur dioxide (mol. wt. = $64$). The pressure exerted by the mixture is $210 \ mm$. If the partial pressures of helium, methane and sulphur dioxide are $p_1, p_2$ and $p_3$ respectively, which one of the following is correct?

$A$ closed vessel contains an equal number of nitrogen and oxygen molecules at a pressure of $P \ mm$. If nitrogen is removed from the system,then the pressure will be