The standard heat of combustion of liquid ethyl cyclopentane, c7h14(6), was measured to be -4589.6 kj/mol. what is the standard heat of formation of liquid ethyl cyclopentane?

ΔHf C₇H₁₄ = 137.6 kJ/mol

Explanation:

The following equation represents the combustion of liquid cyclopentane:

C₇H₁₄ (l) + 10,5O₂ (g) → 7CO₂ (g) + 7H₂O (g)  

The standard heat of combustion for this reaction is ΔHc = -4589.6 kJ/mol.

ΔHc can be calculated by the following equation:

ΔHc = ∑ΔHf products + ∑ΔHf reactants

ΔHc = (7ΔHf CO₂ + 7ΔHf H₂O) - (ΔHf C₇H₁₄ + 10.5ΔHf O₂)

Therefore, we can calculate the standard heat of formation of C₇H₁₄ :

ΔHf C₇H₁₄ = - ΔHc +7ΔHf CO₂+7ΔHf H₂O - 10.5ΔHf O₂

ΔHc = -4589.6 kJ/mol, ΔHf CO₂ = -394.0 kJ/mol, ΔHf H₂O = -242.0 kJ/mol, ΔHf O₂ = 0

ΔHf C₇H₁₄ = 4589.6 + 7x(-394.0) + 7x(-242.0) - 10.5x0

ΔHf C₇H₁₄ = 137.6 kJ/mol

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