
- A$0$
- ✓$2$
- C$3$
- D$4$


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$CH_3OH(l)+ \frac{3}{2} O_2 (g) $$\rightarrow CO_2 (g)+ 2H_2O(l)$
At $298\, K$ standard Gibb's energies of formation for $CH_3OH(l),H_2O(l)$ and $CO_2 (g)$ are $-166.2,-237.2$ and $-394.4\, kJ\,mol^{-1}$ respectively. If standard enthalpy of combustion of methonal is $-726 \,kJ\, mol^{-1},$ efficiency of the fuel cell will be .......... $\%$.
$\mathrm{A}+\mathrm{B} \underset{\text { Step } 3}{\text { Step } 1} \mathrm{C} \xrightarrow{\text { Step } 2} \mathrm{P}$
Some details of the above reaction are listed below.
| Step |
Rate constant $\left(\sec ^{-1}\right)$ |
Activation energy $\left(\mathrm{kJ} \mathrm{mol}^{-1}\right)$ |
| $1$ | ${k}_1$ | $300$ |
| $2$ | ${k}_2$ | $200$ |
| $3$ | ${k}_3$ | $\mathrm{Ea}_3$ |
If the overall rate constant of the above transformation (k) is given as $\mathrm{k}=\frac{\mathrm{k}_1 \mathrm{k}_2}{\mathrm{k}_3}$ and the overall activation energy $\left(E_2\right)$ is $400 \mathrm{~kJ} \mathrm{~mol}^{-1}$, then the value of $\mathrm{Ea}_3$ is $\qquad$ $\mathrm{kJ} \mathrm{mol}^{-1}$ (nearest integer)
${C_6}{H_6}\left( l \right) + \frac{{15}}{2}{O_2}\left( g \right) \longrightarrow 6C{O_2}\left( g \right) + 3{H_2}O\left( l \right)\,;\,\Delta H = - 3271\,kJ$
What is $\Delta U$ for the combustion of $1.5\, mole$ of benzene at $27\,^oC$. .....$ kJ$
$C{S_2}(g) + 4{H_2}(g) \to C{H_4}(g) + 2{H_2}S(g)$