Textbook Question
Use the heat equation to calculate the energy, in joules and calories, for each of the following (see TABLE 3.11):
c. lost when 15.0 g of ethanol, C2H6O, cools from 60.5 °C to −42.0 °C
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Ch.3 Matter and Energy
Timberlake14th EditionChemistry: An Introduction to General, Organic, and Biological ChemistryISBN: 9781292472249
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Table of contents
- Ch.1 Chemistry in Our Lives19
- Ch.2 Chemistry and Measurements80
- Ch.3 Matter and Energy53
- Ch.4 Atoms and Elements58
- Ch.5 Nuclear Chemistry42
- Ch.6 Ionic and Molecular Compounds57
- Ch.7 Chemical Quantities and Reactions38
- Ch.8 Gases30
- Ch.9 Solutions50
- Ch.10 Acids and Bases and Equilibrium64
- Ch.11 Introduction to Organic Chemistry: Hydrocarbons77
- Ch.12 Alcohols, Thiols, Ethers, Aldehydes, and Ketones82
- Ch.13 Carbohydrates54
- Ch.14 Carboxylic Acids, Esters, Amines, and Amides91
- Ch.15 Lipids61
- Ch.16 Amino Acids, Proteins, and Enzymes84
- Ch.17 Nucleic Acids and Protein Synthesis86
- Ch.18 Metabolic Pathways and ATP Production73
Timberlake14th EditionChemistry: An Introduction to General, Organic, and Biological ChemistryISBN: 9781292472249Not the one you use?Change textbook
Chapter 3, Problem 40a
Using the energy values for foods (see TABLE 3.7), determine each of the following (round off the answer for each food type to the tens place):
a. the total kilojoules in two tablespoons of crunchy peanut butter that contains 6 g of carbohydrate, 16 g of fat, and 7 g of protein
Verified step by step guidance1
Identify the energy values for each macronutrient from Table 3.7: carbohydrates provide 17 kJ/g, fats provide 37 kJ/g, and proteins provide 17 kJ/g.
Calculate the energy contribution from carbohydrates by multiplying the mass of carbohydrates (6 g) by the energy value for carbohydrates (17 kJ/g). Use the formula: , where is the mass and is the energy value.
Calculate the energy contribution from fats by multiplying the mass of fats (16 g) by the energy value for fats (37 kJ/g). Use the same formula as in Step 2.
Calculate the energy contribution from proteins by multiplying the mass of proteins (7 g) by the energy value for proteins (17 kJ/g). Again, use the same formula as in Step 2.
Add the energy contributions from carbohydrates, fats, and proteins to determine the total energy content in kilojoules. Use the formula: .
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Macronutrient Energy Values
Macronutrients—carbohydrates, fats, and proteins—provide energy measured in kilojoules (kJ). Carbohydrates and proteins each provide approximately 17 kJ per gram, while fats provide about 37 kJ per gram. Understanding these values is essential for calculating the total energy content of food based on its macronutrient composition.
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Bond Energy
Energy Calculation
To determine the total energy in a food item, multiply the grams of each macronutrient by its respective energy value. For example, in the case of peanut butter, you would calculate the energy from carbohydrates, fats, and proteins separately and then sum these values to find the total kilojoules.
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Rounding Off Numbers
Rounding off is a mathematical process used to simplify numbers to a specified degree of accuracy. In this context, rounding to the tens place means adjusting the final energy total to the nearest ten kilojoules, which helps in presenting the data in a more manageable and understandable format.
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Related Practice
Textbook Question
If the same amount of heat is supplied to samples of 10.0 g each of aluminum, iron, and copper all at 15.0 °C, which sample would reach the highest temperature (see TABLE 3.11)?
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Textbook Question
Using the energy values for foods (see Table 3.8), determine each of the following (round off the answer for each food type to the tens place): d. the grams of fat in one avocado that has 410 kcal, 13 g of carbohydrate, and 5 g of protein
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Textbook Question
For dinner, Charles had one cup of clam chowder, which contains 16 g of carbohydrate, 12 g of fat, and 9 g of protein. How much energy, in kilocalories and kilojoules, is in the clam chowder? (Round off the answer for each food type to the tens place.)
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Textbook Question
A patient receives 3.2 L of intravenous (IV) glucose solution. If 100. mL of the solution contains 5.0 g of glucose (carbohydrate), how many kilocalories did the patient obtain from the glucose solution?
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Textbook Question
Identify each of the following changes of state as melting, freezing, sublimation, or deposition:
b. Snow on the ground turns to liquid water.
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