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MHT CET202019 Oct 2020Evening ShiftChemistryThermodynamics (C)Actual

What is standard N N bond enthalpy from following reaction? N _ 2_ ( g ) +3 H _ 2_ ( g ) 2 NH _ 3_ ( g ) H ^ =-83 KJ ( H ^ _ ( H - H ) =435 ~kJ , H ^ _ ( N - H ) =389 ~kJ )

Options

  1. A435 kJ
  2. B2334 ~kJ
  3. C946 ~kJ
  4. D1305 ~kJ

Correct answer

C. 946 ~kJ

Step-by-step solution

(C) N _ 2(8) +3 H _ 2(8) 2 NH _ 3(8) H ^ =-83 ~kJ H ⁰= H ⁰ (reactant bonds) - H ⁰ (product bonds) . H⁰= [ H⁰ _ (N=N) ⁰+3 H⁰ ⁰ H-H ) ]- [6 H⁰ ⁰(N-H) ] -83= H_ (N=N) ⁰+3(435)-6(389) -83= H_ (N=N) ⁰+1305-2334 H⁰(N N)=-83-1305+2334=946 ~kJ

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