MCQ
When $5$ mole of reactant $A$ reacts with $8$ mole of reactant $B$ in a closed rigid container according to reaction
$3A(g) + 4B(g) \to 2C(g)$
$10^2\, kJ$ heat was librated in surrounding. The $\Delta_rH$ of the given balanced reaction in $(kJ/mole)$ at $300\, K$ is. $[R = 8\, J/mol/K]$
  • A
    $-88$
  • $-72$
  • C
    $-48$
  • D
    $-60$

Answer

Correct option: B.
$-72$
b
Given that , $\mathop {3A(g)}\limits_{5\,mol}  + \mathop {4B(g)}\limits_{8\,mol}  \to 2C(g)$

Limiting reagent is $A$ so if $5$ mol of $A$ reacts then energy liberated $=10^{2} \,\mathrm{kJ}$ then for $3$ mole is $60\, \mathrm{kJ}$.

$\boxed{\Delta H = \Delta E + \Delta {n_g}RT}$

$\Delta E=-60\,kJ$

$\Delta n_{e}=-5$

$\Delta \mathrm{H}=-60+(-5) \,\mathrm{R} \times 300 \times 10^{-3}=-60-1500$

$\times 10^{-3} \,\mathrm{R}=-(60+1.5\, \mathrm{R})$

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