Q6(a)(i). Energy change of HCl + D₂ → DCl + HD
The frequencies of vibration of the following molecules in their v = 0 states are HCl: 2885 cm⁻¹; D₂: 2990 cm⁻¹; DCl: 1990 cm⁻¹ and HD: 3627 cm⁻¹. Calculate the energy change of the reaction HCl + D₂ → DCl + HD. Determine whether energy is liberated or absorbed. [Given: h = 6.626 × 10⁻³⁴ J s; c = 2.998 × 10⁸ m s⁻¹; NA = 6.022 × 10²³ mol⁻¹]
Model answer
The free solution for 2023 answers questions 1, 2, 3, 5 and 8, the ones picked in its time plan. Question 6 is answered in full in the Chemistry Paper II, 2021 to 2025 book, with every part of every paper.
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UPSC Civil Services (Main) Chemistry Paper II: Model Answers 2021 to 2025
- All eight questions of each paper, with the question printed above its answer
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Coverszero-point energyvibrational frequencyisotope exchangeharmonic oscillatorenergy change
All parts of Question 6
- 6(a)(i) Energy change of HCl + D₂ → DCl + HD10 marks
- 6(a)(ii) C=O bands of butyric acid, its ethyl ester and its anhydride5 marks
- 6(b)(i) Products A, B and C10 marks
- 6(b)(ii) Tacticity: isotactic, syndiotactic and atactic polymers5 marks
- 6(c)(i) Structure of C₁₆H₂₅NO from IR and ¹H NMR10 marks
- 6(c)(ii) Order of chemical shift of the lettered protons10 marks