JEE Main 2015ChemistryThermodynamics (C)HardMCQ

JEE Main 2015 — Thermodynamics (C) Question with Solution

JEE Main 2015 (10 Apr Online)

Question

The heat of atomization of methane and ethane are 360 kJ mol-1 and 620 kJ mol-1, respectively. The longest wavelength of light capable of breaking the C-C bond is (Avogadro's number=6.023×1023, h=6.62×10-34 J s)

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Show full solutionCorrect option: D
Correct answer
D1.49×103  nm

Step-by-step explanation

4 B.E (C-H) bond=360 kJ mol-1.

B.E (C-H) bond=90 kJ mol-1.

In C2H6, B.EC-C+6×B.EC-H=620 kJ,

B.EC-C bond=620-6×90=80 kJ mol-1,

B.EC-C bond=8096.48=0.83 eV bond-1.

λ(Photon in Å) for rupture of

E=hcλ
The wave length required to break C-C bond=124080.83=14950Å,

=1495 nm,

≈1.49×103 nm.

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About this question

This is a previous-year question from JEE Main 2015, covering the Thermodynamics (C) chapter of Chemistry. PrepSharp catalogues every PYQ from JEE Main with a verified answer key and step-by-step solution prepared by IIT alumni — so you can search by chapter, topic or year and revise efficiently.