The heat of combustion of solid benzoic acid ( C 7 H 6 O 2 ) at constant volume is -321.30 kJ at 2 7 ∘ C . The heat of combustion at constant pressure is

C₆H₅COOH(s) + 15/2 O₂ ⟶7CO₂(g) + 3H₂O(l) Δ n g = 7 − ( 2 15 ) = − 2 1 Δ H = Δ U + Δ n g RT Given Δ n g = − 2 1 , then Δ H = − 321.30 − 150 × R .

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The heat of combustion of solid benzoic acid $(C_{7} H_{6} O_{2})$ at constant volume is -321.30 kJ at $2 7^{\circ} C$ . The heat of combustion at constant pressure is

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Solution:

C₆H₅COOH(s) + 15/2 O₂ ⟶7CO₂(g) + 3H₂O(l)

$Δ n_{g} = 7 - (\frac{15}{2}) = - \frac{1}{2}$

$Δ H = Δ U + Δ n_{g} RT$

Given $Δ n_{g} = - \frac{1}{2}$ , then $Δ H = - 321.30 - 150 \times R$ .

Stream:JEESubject:ChemistryTopic:ThermochemistrySubtopic:Enthalpy of Combustion

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