UPSC Combined Geo-Scientist, Mains · 2021 · Mains Paper II
Q12(b). Activation energy of N₂O₅ decomposition from A and k
Question
For the first order reaction 2N₂O₅(g) → 4NO₂(g) + O₂(g), A is 4.3 × 10¹³ s⁻¹ and k is 4.329 × 10⁻⁵ s⁻¹; calculate the energy of activation at 300 K.
Answer in brief
Ea = RT ln(A/k) = (2494.2)(41.440) = 1.034 × 10⁵ J mol⁻¹ = 103.4 kJ mol⁻¹ (24.7 kcal mol⁻¹).
Part of VKC Basic
Read the key points and the full model answer with VKC Basic
VKC Basic (₹999 for 6 months) opens every solved answer, the notes, the handbook and the daily answer archive. Every Mains test series includes it.
The full model answer
As written for the answer booklet: the diagram carries the working, the lines stay short. Read here only; it is not offered as a download.
The handwritten model answer pages open with the VKC plan.
Coversactivation energyArrhenius equationpre-exponential factorN2O5 decompositionfirst order reaction
All parts of Question 12
- 12(a) Gibbs–Duhem equation Σ ni dȲi = 0 and its meaning10 marks
- 12(b) Activation energy of N₂O₅ decomposition from A and k10 marks