Chemistry - Thermochemistry Question with Solution | TestHub
ChemistryThermochemistryEnthalpy of CombustionMedium2 minQB
ChemistryMediumsingle choice
Passage / Comprehension
When 0.1 mole of C6H14(l) at 300 K is completely burned at constant pressure in some oxygen gas at 300 K, yielding products gaseous H2O, CO and CO2 at 700 K, the process yielding 75.16 kcal of heat to the surrounding. Given:
Δf H (kcal/mol): C6H14(l) = -40.0, CO2(g) = -94.0, CO(g) = -26.0, H2O(g) = -58.0
Molar heat capacity at constant pressure (cal/K-mol): CO(g) = 7.0, CO2(g) = 9.0, H2O(g) = 8.0
Assume that all Δr H are independent of temperature and R = 2 cal/K-mol.
The value of Δc H of C6H14(l) (forming CO2(g) and H2O(g)) is (in kcal/mol)
Options:
Answer:
D
Solution:
C6H14(l) + 19/2O2 → 6CO2 + 7H2O(g). Δc H = 6(-94.0) + 7(-58.0) - (-40.0) = -564 - 406 + 40 = -930 kcal/mol. This is option (d).
Stream:JEESubject:ChemistryTopic:ThermochemistrySubtopic:Enthalpy of Combustion
⏱ 2mℹ️ Source: QB
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