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MHT CET202014 Oct 2020Morning ShiftChemistryThermodynamics (C)Actual

Heat of combustion of C _ ( s ) , H _ 2( ~g ) and C ₂ H _ 6( ~g ) are -x₁,-x₂ and -x₃ respectively. Hence heat of formation of C ₂ H _ 6( ~g ) is

Options

  1. A-x₁-x₂+x₃
  2. B-2 x₁-3 x₂+x₃
  3. Cx₁+x₂-x₃
  4. D-x₃+2 x₁+3 x₂

Correct answer

B. -2 x₁-3 x₂+x₃

Step-by-step solution

i. C + O ₂ CO ₂ H ₁=- x ₁ ii. H ₂+ 1 2 O ₂ H ₂ O H ₂=- x ₂ iii. C ₂ H ₆+ 7 2 O ₂ 2 CO ₂+3 H ₂ O H ₃=- x ₃ Multiply equation (i) by 2+ multiply equation (ii) by 3 - equation (iii) array l 2 C +3 H ₂ C ₂ H ₆ H =2 H ₁+3 H ₂- H ₃ H =-2 x ₁-3 x ₂+ x ₃ array

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