At STP, a closed vessel contains I mole each of He and $\mathrm{CH}_4$. Through a small hole, 2 L of He and LL of $\mathrm{CH}_4 \mathrm{WHS}$ escaped from vessel in ' $t$ ' minutes. What are the mole fractions of He and $\mathrm{CH}_4$ respectively remaining in the vessel? ( Assume He and $\mathrm{CH}_4$ as ideal gases. At STP one mole of an ideal gas occupies 22.4 L of volume.)

What is the enthalpy change (in J ) for converting 98 of $\mathrm{H}_2 \mathrm{O}(t)+10^{\circ} \mathrm{C}$ to $\mathrm{H}_2 \mathrm{O}(l)$ at $+20^{\circ} \mathrm{C}$ ?

$$ \left(C_p\left(\mathrm{H}_2 \mathrm{O}(\eta)\right)=75 \mathrm{Jmol}^{-1} \mathrm{~K}^{-1}\right) $$

(density of $\mathrm{H}_2 \mathrm{O}(l)=1 \mathrm{gmL}^{-1}{ }^{})$

$A, B, C$ and $D$ are some compounds. The entnalpy of formation of $A(g), B(g), C(g)$ and $D(g)$ is $9.7,-110,81$ and $-393 \mathrm{~kJ} \mathrm{~mol}^{-1}$ respectively. What is $\Delta_r H$

(in $\mathrm{kJ} \mathrm{mol}^{-1}$ ) for the given reaction ?

$$ A(g)+3 B(g) \longrightarrow C(g)+3 D(g) $$