Two gases $A$ and $B$ having the same volume diffuse through a porous partition in $20$ and $10$ seconds respectively. The molecular mass of $A$ is $49 \ u$. The molecular mass of $B$ will be .............. $u$.

Which of the following statements is incorrect?

$A$ closed vessel contains an equal number of molecules of $N_2$ and $O_2$ at a pressure of $650 \ mm$. If $N_2$ is completely removed,what will be the pressure in the vessel?

In a container,the mole ratio of two gases $A$ and $B$ is $2 : 5$. The total pressure of the container is $3.5 \times 10^5 \ Pa$. If all molecules of $A$ are removed from the container,what will be the pressure exerted by the molecules of $B$?

$A$ container consists of a mixture of $28 \ g \ N_2$,$8 \ g \ He$,and $40 \ g \ Ne$ at $25^{\circ} C$. If the total pressure exerted by the gaseous mixture is $20 \ bar$,what is the partial pressure exerted by $N_2$ (in $bar$)?

The rate of diffusion of a gas (molar mass = $128$) compared to oxygen is: