Question

Myristic acid (C14H28O2)(C14H28O2) is a dietary fat found in palm oil, coconut oil, and butter. The caloric content of myristic acid is typical of fats in general.

B. Calculate the standard enthalpy of combustion. The standard enthalpy of formation of myristic acid is −834 kJ/mol that of CO2(g) is −393.5 kJ/mol, and that of H2O(l) is −285.8 kJ/mol. Express your answer in kilojoules per mole as an integer.
C. What is the caloric content of myristic acid in Cal/g? Express your answer in Calories per gram to four significant figures.
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.) Express your answer as a chemical equation including phases.
E. Calculate the standard enthalpy of combustion. The standard enthalpy of formation of sucrose is −2226.1kJ/mol, that of CO2(g) is −393.5 kJ/mol, and that of H2O(l) is −285.8 kJ/mol. Express your answer in kilojoules per mole to one decimal place.
F. What is the caloric content of sucrose in Cal/g?

Answer 1

B.

Standard enthalpy of formation of myristic acid: -834 kJ/mol

Enthalpy of formation of CO2(g): -393.5 kJ/mol

Enthalpy of formation of H2O(l): -285.8 kJ/mol

Standard enthalpy of combustion = -834 + (-393.5 x 2) + (-285.8 x 3) = -1451 kJ/mol

Express as integer: -1451 kJ/mol

C.

Caloric content = 1400 kJ/mol (standard enthalpy of combustion converted to cal/mol)

MW of myristic acid = 228.36 g/mol

So caloric content = 1400 / 228.36 = 6106 Cal/mol

Express as 4 significant figures: 6106 Cal/g

D.

C12H22O11 + 12O2 → 12CO2 + 11H2O (l)

E. Standard enthalpy of formation of sucrose: -2226.1 kJ/mol

Enthalpy of formation of CO2(g): -393.5 kJ/mol

Enthalpy of formation of H2O(l): -285.8 kJ/mol

Standard enthalpy of combustion = -2226.1 + (-393.5 x 12) + (-285.8 x 11) = -2821.9 kJ/mol

Express as one decimal place: -2822.0 kJ/mol

F.

Caloric content = 2822 kJ/mol (standard enthalpy of combustion)

MW of sucrose = 342.3 g/mol

So caloric content = 2822 / 342.3 = 8276 Cal/mol

Express as 4 significant figures: 8276 Cal/g