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NEET UG 2018 · Chemistry · Question 85

NEET 2018 Chemistry, question 85

Question 85 of the NEET 2018 paper (code AA) is a Chemistry question from Thermodynamics. Its idea, Bond Enthalpy Calculations, was asked only this once in NEET 2017–2026. The CBSE official answer key gives option 1.

Updated 2026-10-08

Q85 · Chemistry

The bond dissociation energies of X2\mathrm{X_2}, Y2\mathrm{Y_2} and XY are in the ratio of 1 : 0.5 : 1. ΔH\Delta H for the formation of XY is – 200 kJ mol−1^{-1}. The bond dissociation energy of X2\mathrm{X_2} will be

  1. 1800 kJ mol−1^{-1}Official answer
  2. 2100 kJ mol−1^{-1}
  3. 3200 kJ mol−1^{-1}
  4. 4400 kJ mol−1^{-1}

Official answer: option 1 · CBSE official answer key

Same idea

The only question on Bond Enthalpy Calculations

No other NEET paper from 2017–2026 tested this exact idea.

Bond Enthalpy Calculations: every question and how it was framed

The chapter

Thermodynamics in ten years of NEET

32 questions from 2017–2026, asked in 10 of 10 papers, about 3.1 a paper. Enthalpy and Hess's Law alone had 4.

Chapter analysisStudy this chapterPractise this chapter

Thermodynamics: questions per paper

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