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Chemical Kinetics and Nuclear Chemistry question

2021 · 31 Aug · Shift 1 · Q19
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Chemical Kinetics and Nuclear Chemistry question

2021 · 31 Aug · Shift 1 · Q19

JEE MainChemistryChemical Kinetics and Nuclear ChemistryNumerical+4 / −1
According to the following figure, the magnitude of the enthalpy change of the reaction A + B →\to→ M + N in kJ mol −-− is equal to ‾\underline{\hspace{2cm}}​. (Integer answer) JEE Main 2021 (Online) 31st August Morning Shift Chemistry - Chemical Kinetics and Nuclear Chemistry Question 97 English
Numerical answer
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Correct answer: 45

  1. For a reaction profile,

ΔH=Hproducts−Hreactants\Delta H = H_{\text{products}} - H_{\text{reactants}}ΔH=Hproducts​−Hreactants​

and the magnitude of enthalpy change is

∣ΔH∣=∣Hproducts−Hreactants∣.|\Delta H| = |H_{\text{products}} - H_{\text{reactants}}|.∣ΔH∣=∣Hproducts​−Hreactants​∣.

  1. From the figure, the energy difference between the reactants A+BA+BA+B and the products M+NM+NM+N is obtained by comparing their energy levels.

  2. Reading the diagram, the products are lower than the reactants by

45 kJ mol−1.45\ \text{kJ mol}^{-1}.45 kJ mol−1.

So,

ΔH=−45 kJ mol−1\Delta H = -45\ \text{kJ mol}^{-1}ΔH=−45 kJ mol−1

and therefore its magnitude is

∣ΔH∣=45 kJ mol−1.|\Delta H| = 45\ \text{kJ mol}^{-1}.∣ΔH∣=45 kJ mol−1.

  1. Hence, the required integer answer is

45.\boxed{45}.45​.

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