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NEET2006ChemistryThermodynamics (C)Actual

The enthalpy of combustion at 25^ C of H ₂ , cyclohexane ( C ₆ H ₁₂ ) and cyclohexene ( C ₆ H ₁₀ ) are -241,-3920 and -3800 ~kJ / mol respectively. The heat of hydrogenation of cyclohexene is :

Options

  1. A-121 ~kJ / mol
  2. B+121 ~kJ / mol
  3. C-242 ~kJ / mol
  4. D+242 ~kJ / mol

Correct answer

A. -121 ~kJ / mol

Step-by-step solution

aligned & H ₂+ 1 2 O ₂ H ₂ O & H=-241 ~kJ . . aligned aligned C ₆ H ₁₀+ 17 2 O ₂ 6 CO ₂+5 H ₂ O H=-3800 ~kJ (ii) aligned aligned C ₆ H ₁₂+9 O ₂ & 6 CO ₂+6 H ₂ O & H=-3920 ~kJ (iii) aligned hydrogenation of cyclohexene- aligned & C ₆ H ₁₀+ H ₂ C ₆ H ₁₂ & Eq (i) aligned Eq & (ii) - Eq (iii) H & =-241-3800-(-3920) & =-4041+3920 & =-121 ~kJ aligned aligned

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