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AP EAMCET201726 Apr 2017Morning ShiftChemistryThermodynamics (C)Actual

The enthalpy of formation ( H _f ) of methanol, formaldehyde and water are -239,-116 and -286 ~kJ ~mol ⁻¹ respectively. The enthalpy change for the oxidation of methanol to formaldehyde and water in kJ is

Options

  1. A-136
  2. B-173
  3. C163
  4. D-163

Correct answer

D. -163

Step-by-step solution

Given H_f for CH ₃ OH =-239 ~kJ ~mol ⁻¹ H_f of H . CHO =-116 ~kJ ~mol ⁻¹ H_f of H ₂ O =-286 ~kJ ~mol ⁻¹ Required relation: aligned & 2 CH ₃ OH + O ₂ 2 HCHO +2 H ₂ O & H_R= 1 2 H_ f^ [(2 x-116)+(2 x-286)] & -1[(2 239)] & _r H= ( _f H_ Product )- ( _f H_ Reactant ) & =(-116+(-286))-(-293+0) & =-163 ~kJ ~mol ⁻¹ aligned

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