To which of the following gaseous mixtures is Dalton's law of partial pressures not applicable?

Which of the following property of a small drop of mercury can be used to explain the spherical shape of mercury droplets?

At $400 \ K$ temperature in a closed vessel,the $\%$ by volume of $He, Ne$,and $Ar$ are $40\%, 40\%$,and $20\%$ respectively. If the total pressure is $25 \ bar$,find the partial pressure of each gas.

$A$ sample of air contains $N_2$ and $O_2$ saturated with water vapor,with a total pressure of $640 \ torr$. If the water vapor pressure is $40 \ torr$ and the molar ratio of $N_2$ to $O_2$ is $3 : 1$,what is the partial pressure of $N_2$ in the sample in $torr$?

Internal energy of an ideal gas depends on

$1 \ L$ each of gases $A$ and $B$ diffused through a membrane in $15$ and $30$ minutes, respectively, under identical conditions. What is the ratio of molecular weight of $A$ and $B$?