The standard enthalpies of formation of , , and solid glucose at 25 C are -400, -300, and -1300 kJ/m — Thermodynamics and Thermochemistry Chemistry Question
Question
The standard enthalpies of formation of $CO_2(g)$, $H_2O(l)$, and solid glucose at 25 C are -400, -300, and -1300 kJ/mol respectively. Calculate the absolute magnitude of the standard enthalpy of combustion per gram of glucose. (Molar mass = 180 g/mol)
Answer: A
💡 Solution & Explanation
Combustion of glucose: $C_6H_{12}O_6 + 6O_2 \rightarrow 6CO_2 + 6H_2O$. $\Delta H = [6(-400) + 6(-300)] - (-1300) = -2400 - 1800 + 1300 = -2900$ kJ/mol. Heat released per gram = $2900 / 180 = 16.11$ kJ/g.
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