Palmitic acid (C_16 H_32 O_2) is a dietary that found in beef and butter. The ca

Question

Palmitic acid (C_16 H_32 O_2) is a dietary that found in beef and butter. The caloric content of palmitic acid is typical of fats in general. Write a balanced equation for the complete combustion of palmitic acid and calculate the standard enthalpy of combustion. a) What is the caloric content of palmitic acid in kcal/g? Delta H_f (C_16 H_3 O_2) = -208 kJ/mol. Since this is a metabolic "combustion" water is produced in the liquid phase. b) Do the same calculation for sugar (sucrose. C_12 O_22 O_11), Delta H_f (C_12 H_22 O_11) = -2226.1 kJ/mol c) Which dietary substance (sugar or fat) contains more calories per gram?

Explanation / Answer

The general Balanced equation for combustion of palmitic acid is as follows:

C16H32O2(s) + 23O2(g) ---> 16CO2(g) + 16H2O(l)

Now calculate the t caloric content of plamitic acid:

dHcomb = dHoproducts - dHoreactants

                   = (16 x -393.51 + 16 x -285.8) - (-208)

                   = -10660.96 kJ/mol

caloric content = -10660.96/256.424 g/mol x 4.184 = -9.936 cal/g

The general Balanced equation for combustion of sucrose is as follows:

C12H22O11(s) + 12O2(g) ---> 12CO2(g) + 11H2O(l)

caloric content dHcomb = dHoproducts - dHoreactants

                   = (12 x -393.51 + 11 x -285.8) - (-2226.1)

                   = -5639.82 kJ/mol

caloric content = -5639.82/343.2965 g/mol x 4.184 = -3.938 cal/g

thus palmiti acid has higher caloric content than sugar,.

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