Palmitic acid (C16H32O2) is a dietary fat found in beef and butter. The caloric

Question

Palmitic acid (C16H32O2) is a dietary fat found in beef and butter. The caloric content of palmitic acid is typical of fats in general.

A) Write a balanced equation for the complete combustion of solid palmitic acid. Use H2O(l) in the balanced chemical equation because the metabolism of these compounds produces liquid water.

B) Calculate the standard enthalpy of combustion. The standard enthalpy of formation of palmitic acid - 208kJ/mol.

C) What is the caloric content of palmitic acid in Cal/g?

D) Write a balanced equation for the complete combustion of table sugar (sucrose, C12H22O11). Use H2O(l) in the balanced chemical equation because the metabolism of these compounds produces liquid water.

E) Calculate the standard enthalpy of combustion. The standard enthalpy of formation of sucrose is - 2226.1kJ/mol.

F) What is the caloric content of sucrose in Cal/g?

Explanation / Answer

A) Balanced equation,

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

B) dHcomb = dHoproducts - dHoreactants

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

                   = -10660.96 kJ/mol

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

D) Balanced equation,

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

E) dHcomb = dHoproducts - dHoreactants

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

                   = -5639.82 kJ/mol

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

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