Equal masses of three non-reacting different ideal gases $X, Y$ and $Z$ are mixed in a sealed rigid container. If the temperature of the system remains constant at $400 \ K$,which of the following statements about gas $X$ can never be correct?

Which one of the following equations represents the variation of viscosity coefficient $(\eta)$ with temperature $(T)$?

$A$ fixed mass '$m$' of a gas is subjected to a transformation of states from $K$ to $L$ to $M$ to $N$ and back to $K$ as shown in the figure.
$1.$ The succeeding operations that enable this transformation of states are:
$(A)$ Heating,cooling,heating,cooling
$(B)$ Cooling,heating,cooling,heating
$(C)$ Heating,cooling,cooling,heating
$(D)$ Cooling,heating,heating,cooling
$2.$ The pair of isochoric processes among the transformation of states is:
$(A)$ $K$ to $L$ and $L$ to $M$
$(B)$ $L$ to $M$ and $N$ to $K$
$(C)$ $L$ to $M$ and $M$ to $N$
$(D)$ $M$ to $N$ and $N$ to $K$
Give the answer for question $1$ and $2$.

Which of the following statements is correct?

The density of a mixture of $He$ and $O_2$ gases at $27\,^{\circ}C$ and $760\, torr$ pressure is $0.543\, g\, dm^{-3}$. Calculate the percentage by mass of $He$ in the mixture.

If $4 \ g$ of oxygen diffuses through a narrow hole under identical conditions,how many grams of hydrogen will diffuse?