An exothermic reaction $\mathrm{X} \rightarrow \mathrm{Y}$ has an activation energy $30 \mathrm{~kJ} \mathrm{~mol}^{-1}$. If energy change $\Delta \mathrm{E}$ during the reaction is $-20 \mathrm{~kJ}$, then the activation energy for the reverse reaction in kJ is ______ (Integer answer)

JEE Main · 2021 · 26 Feb 2021 · Shift 1 · Chemical Kinetics

An exothermic reaction

X \to Y

has an activation energy

30 kJ mol^{- 1}

. If energy change

Δ E

during the reaction is

- 20 kJ

, then the activation energy for the reverse reaction in kJ is ______ (Integer answer)

Answer: 50

Solution

On the energy profile the forward activation energy is measured from the reactants to the top of the barrier and the reverse one from the products to that same top, so the two differ by the energy change of the reaction:

E_{a} (reverse) = E_{a} (forward) - Δ E

The reaction is exothermic, so the products lie below the reactants and the barrier seen from the product side is the taller one. With

E_{a} (forward) = 30 kJ mo l^{- 1}

and

Δ E = - 20 kJ mo l^{- 1}

E_{a} (reverse) = 30 - (- 20) = 50

The activation energy of the reverse reaction is

50

mo l^{- 1}

JEE Main · 2021 · 26 Feb 2021 · Shift 1 · Integer answer

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JEE Main · 2021 · 26 Feb 2021 · Shift 1 · Chemical Kinetics

Solution

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