$A$ tube of length $1 \, m$ has identical pinholes at both ends. Ammonia gas at $1 \, atm$ pressure is introduced from one end,and $HCl$ gas at $P \, atm$ pressure is introduced from the other end at room temperature. If $NH_4Cl$ is formed at a distance of $60 \, cm$ from the end where $HCl$ was introduced,calculate the value of pressure $P$. (in $, atm$)

Match gases under specified conditions listed in Column-$I$ with their properties/laws in Column-$II$.

Column-$I$	Column-$II$
$A$. Hydrogen gas $(P=200 \ atm, T=273 \ K)$	$p$. Compressibility factor $Z \neq 1$
$B$. Hydrogen gas $(P \approx 0, T=273 \ K)$	$q$. Attractive forces are dominant
$C$. $CO_2$ $(P=1 \ atm, T=273 \ K)$	$r$. $PV=nRT$
$D$. Real gas with very large molar volume	$s$. $P(V_m-b)=RT$

Fill in the blanks:
$(1)$ Gases like $CO_2$ and $CH_4$ show ............ deviation from ideal gas behavior.
$(2)$ The temperature at which a real gas obeys ideal gas laws over an appreciable range of pressure is called ............ .
$(3)$ The maximum temperature below which a gas can be liquefied is called ............ .
$(4)$ The unit of coefficient of viscosity in the $CGS$ system is ............ .

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:

$A$ $4 : 1$ molar mixture of $He$ and $CH_4$ is kept in a vessel at $20 \ bar$ pressure. Due to a hole in the vessel,the gas mixture leaks out. What is the composition of the mixture effusing out initially?

Which of the following has higher surface tension: pure water or soapy water?