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NEET2009ChemistryThermodynamics (C)Actual

From the following bond energies : H - H bond energy : 431.37 ~kJ ~mol ⁻¹ C = C bond energy : 606.10 ~kJ ~mol ⁻¹ C - C bond energy : 336.49 ~kJ ~mol ⁻¹ C - H bond energy : 410.50 ~kJ ~mol ⁻¹ Enthalpy for the reaction, will be

Options

  1. A1523.6 ~kJ ~mol ⁻¹
  2. B-243.6 ~kJ ~mol ⁻¹
  3. C-120.0 ~kJ ~mol ⁻¹
  4. D553.0 ~kJ ~mol ⁻¹

Correct answer

C. -120.0 ~kJ ~mol ⁻¹

Step-by-step solution

Key Idea Enthalpy of reaction = BE _ Reactants - BE _ Products For reaction, aligned & H _ r = [4 BE _ ( C - H ) +1 BE _ ( C = C ) +1 BE _ ( H - H ) ] & - [6 BE _ ( C - H ) +1 BE _ ( C - C ) ] & =(4 410.50+1 606.10+1 431.37) & -[(6 410.50)+(1 336.49)] & =-120.0 ~kJ ~mol ⁻¹ aligned

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