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Ch.5 - Thermochemistry
Brown - Chemistry: The Central Science 15th Edition
Brown15th EditionChemistry: The Central ScienceISBN: 9780137542970Not the one you use?Change textbook
All textbooksBrown 15th EditionCh.5 - ThermochemistryProblem 95
Chapter 5, Problem 95

The heat of combustion of fructose, C6H12O6, is -2812 kJ/mol. If a fresh golden delicious apple weighing 4.23 oz (120 g) contains 16.0 g of fructose, what caloric content does the fructose contribute to the apple?

Verified step by step guidance
1
Convert the mass of fructose from grams to moles using its molar mass. The molar mass of fructose (C_6H_{12}O_6) is calculated as follows: (6 \(\times\) 12.01) + (12 \(\times\) 1.01) + (6 \(\times\) 16.00) g/mol.
Use the moles of fructose to calculate the total energy released during combustion using the given heat of combustion value (-2812 kJ/mol).
Convert the energy from kilojoules to calories. Remember that 1 calorie = 4.184 joules, so you will need to convert kilojoules to joules first.
Convert the energy from calories to kilocalories (food calories), as nutritional information is typically given in kilocalories. Note that 1 kilocalorie = 1000 calories.
The final value represents the caloric content contributed by the fructose in the apple.

Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Heat of Combustion

The heat of combustion is the amount of energy released when a substance is completely burned in oxygen. It is typically expressed in kilojoules per mole (kJ/mol). For fructose, the heat of combustion is -2812 kJ/mol, indicating that this amount of energy is released when one mole of fructose is oxidized.
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Molar Mass

Molar mass is the mass of one mole of a substance, usually expressed in grams per mole (g/mol). For fructose (C6H12O6), the molar mass is approximately 180.18 g/mol. This value is essential for converting between grams of fructose and moles, which is necessary for calculating the energy content based on the heat of combustion.
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Caloric Content

Caloric content refers to the amount of energy provided by food, typically measured in calories or kilocalories. In this context, the caloric content contributed by fructose in the apple can be calculated by determining how many moles of fructose are present and multiplying by the heat of combustion, allowing us to express the energy contribution in familiar dietary terms.
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Related Practice
Textbook Question

The standard enthalpies of formation of gaseous propyne (C3H4), propylene (C3H6), and propane (C3H8) are +185.4, +20.4, and -103.8 kJ/mol, respectively. (c) Which is the most efficient fuel in terms of heat evolved per unit mass?

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Textbook Question

The heat of combustion of ethanol, C2H5OH(l), is -1367 kJ/mol. A batch of Sauvignon Blanc wine contains 10.6% ethanol by mass. Assuming the density of the wine to be 1.0 g/mL, what is the caloric content due to the alcohol (ethanol) in a 6-oz glass of wine (177 mL)?

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Textbook Question

Two positively charged spheres, each with a charge of 2.0⨉10-5 C, a mass of 1.0 kg, and separated by a distance of 1.0 cm, are held in place on a frictionless track. (a) What is the electrostatic potential energy of this system?

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Textbook Question

(a) A serving of a particular ready-to-serve chicken noodle soup contains 2.5 g fat, 14 g carbohydrate, and 7 g protein. Estimate the number of Calories in a serving.

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Textbook Question

(b) A particular chip snack food is composed of 12% protein, 14% fat, and the rest carbohydrate. What percentage of the calorie content of this food is fat?

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