When equal volumes of helium and neon at same temperature and pressure are mixed,the ratio $C_p: C_V$ of the mixture equals

$A$ and $B$ are ideal gases. The molecular weights of $A$ and $B$ are in the ratio of $1: 4$. The pressure of a gas mixture containing equal weights of $A$ and $B$ is $P \text{ atm}$. What is the partial pressure (in $\text{atm}$) of $B$ in the mixture?

$4 \ g \ CH_4$ and $2 \ g \ He$ are mixed under $NTP$. What is the partial pressure of $He$?

Which of the following gas mixtures is not applicable for Dalton's law of partial pressure?

If the molar ratio of $CH_4$ and $O_2$ is $1:2$,then the ratio of the rate of diffusion of $O_2$ and $CH_4$ is respectively: