The heat evolved on combustion of 1 g of sucrose, C 12 H 22 O 11 , into CO 2 (g) and H 2 O(l) is 3.5 kcal. Heat of formation of CO 2 (g) and H 2 O(l) are -94.2 and -68.4 kcal/mol, respectively. The magnitude of standard enthalpy of formation of 1 g of sucrose (in kcal) is

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ChemistryThermochemistryEnthalpy of CombustionMedium2 minQB

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The heat evolved on combustion of 1 g of sucrose, C₁₂H₂₂O₁₁, into CO₂(g) and H₂O(l) is 3.5 kcal. Heat of formation of CO₂(g) and H₂O(l) are -94.2 and -68.4 kcal/mol, respectively. The magnitude of standard enthalpy of formation of 1 g of sucrose (in kcal) is

Answer:

2.00

Solution:

C₁₂H₂₂O₁₁ + 12O₂ → 12CO₂ + 11H₂O(l); per mole (342 g), ΔH_comb = 342 × (-3.5) = -1197 kcal. Δ_f H(sucrose) = 12(-94.2) + 11(-68.4) - (-1197) = -1130.4 - 752.4 + 1197 = -685.8 kcal/mol = -685.8/342 ≈ -2.0 kcal/g. Magnitude = 2 kcal.

Stream:JEESubject:ChemistryTopic:ThermochemistrySubtopic:Enthalpy of Combustion

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