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AP EAMCET2007ChemistryThermodynamics (C)

Calculate enthalpy for formation of ethylene from the following data (I) C _ (graphite) + O ₂( ~g ) CO ₂( ~g ) H=393.5 ~kJ (II) H ₂(g)+ 1 2 O ₂(g) H ₂ O (l) ; U=-256.2 ~kJ (III) array r C ₂ H ₄(g)+3 O ₂(g) 2 CO ₂(g)+2 H ₂ O (l) ; H=-1410.8 ~kJ array

Options

  1. A54.1 ~kJ
  2. B44.8 ~kJ
  3. C51.4 ~kJ
  4. D48.4 ~kJ

Correct answer

C. 51.4 ~kJ

Step-by-step solution

(I) C + O ₂ CO ₂ ; H=-393.5 ~kJ (II) H ₂+ 1 2 O ₂ H ₂ O ; H=-286.2 ~kJ (III) C ₂ H ₄+3 O ₂ 2 CO ₂+2 H ₂ O ; H=-1410.8 ~kJ Multiply the equations (I) and (II) by 2 (IV) 2 C +2 O ₂ 2 CO ₂ ; H=-787.0 ~kJ (V) 2 H ₂+ O ₂ 2 H ₂ O ; H=-572.4 ~kJ Add the equations (IV) and (V) and then subtract (III). 2 C +2 H ₂ C ₂ H ₄ ; H=51.4 ~kJ

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