A lot of food exists in the form of solid when initially taken up by us. After t

Question

A lot of food exists in the form of solid when initially taken up by us. After they enter the body, they will be digested into small molecules. For instance, rice is mainly composed of solid state polysaccharides that will be decomposed into glucose. Our body is able to metabolize glucose with the aid of oxygen via the mechanism of aerobic respiration. During the oxidation, energy will be released to support the behavior of cells, tissues, and organs. If we need 200 g glucose each day to support our activities, what is the amount of energy released from glucose oxidation? What is the theoretical maximum amount of work can we get from glucose oxidation?

[at a standard condition with 1 bar and 298.15 k, the standard enthalpies of formation of glucose, carbon dioxide, and water are -1274, -394, and -286 KJ/mol, respectively. The entropy of glucose at the standard condition is 209.2 J/mol. The molar heat capacity of glucose is 115 J/K?mol. Please find other needed parameters from the appendix. Please first find standard enthalpy of reaction. Based on this number, please find the answers to the questions.]

Explanation / Answer

formation of glucose is C6H12O6 + 6O2 --> 6 CO2 + 6 H20
- 6*286 -6*394 + 1274 = -2806 kj/mol

now for 200g ... (200/180)*2806 = 3117.77 kj

max work
dG = H- T dS = 115.2 - 298.15*209.2
= -62257.78 J

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