JEE Main 2014ChemistryThermodynamics (C)HardMCQ

JEE Main 2014 — Thermodynamics (C) Question with Solution

JEE Main 2014 (09 Apr Online)

Question

The standard enthalpy of formation of NH3 is - 46.0 kJ/mol. If bond enthalpy of H2 is -436 kJ/mol and that of N2 is -712 kJ/mol , the average bond enthalpy of N-H bond in NH3 is :

Choose an option

Show full solutionCorrect option: D
Correct answer
D+ 352 kJ/mol

Step-by-step explanation

For The Reaction

1 2 N 2 g + 3 2 H 2 g → NH 3 g ; Δ H f ∘ = - 4 6 KJ mol - 1

Δ H f ∘ = - 4 6 = ∑ B.E - ∑ B.E
                              Reactants      Product

∑ B.E = ∑ B.E + 4 6
Product        Reactants

                = 1 2 7 1 2 + 3 2 4 3 6 + 4 6

               = 356 + 654 + 46 = 1056

Averge B.E for N-H Bond  = 1 0 5 6 3 = 3 5 2 KJ mol - 1

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About this question

This is a previous-year question from JEE Main 2014, 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.