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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 94
Chapter 5, Problem 94

A hamburger contains 28 g fat, 46 g carbohydrate, and 25 g protein. What is the fuel value in kJ in one hamburger? How many calories does it provide?

Verified step by step guidance
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Step 1: Identify the energy content per gram for each macronutrient. Typically, fat provides 9 kcal/g, carbohydrates provide 4 kcal/g, and protein provides 4 kcal/g.
Step 2: Calculate the total energy in kilocalories (kcal) for each macronutrient by multiplying the mass of each macronutrient by its respective energy content per gram. For example, for fat: 28 g * 9 kcal/g.
Step 3: Sum the energy contributions from fat, carbohydrates, and protein to find the total energy content in kilocalories for the hamburger.
Step 4: Convert the total energy from kilocalories to kilojoules (kJ) using the conversion factor 1 kcal = 4.184 kJ.
Step 5: Present the total energy content in both kilojoules and kilocalories, ensuring clarity in the units used.

Key Concepts

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

Caloric Value of Macronutrients

Each macronutrient provides a specific amount of energy when metabolized. Fats provide approximately 37 kJ (9 kcal) per gram, carbohydrates provide about 17 kJ (4 kcal) per gram, and proteins also provide around 17 kJ (4 kcal) per gram. Understanding these values is essential for calculating the total energy content of food items.
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Conversion Between Energy Units

Energy can be expressed in different units, such as kilojoules (kJ) and calories (kcal). The conversion factor is 1 kcal = 4.184 kJ. This relationship is crucial for converting the total energy calculated in kJ to calories, allowing for a comprehensive understanding of the energy content in food.
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Conversion Factors

Total Energy Calculation

To find the total energy content of a food item, one must multiply the mass of each macronutrient by its respective caloric value and then sum these values. This process provides the total fuel value in kJ, which can then be converted to calories, giving a complete picture of the food's energy contribution.
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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

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?

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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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