Textbook Question
A sample of glucose, C6H12O6, contains 1.250×1021 carbon atoms. (c) How many moles of glucose does it contain?
Ch.3 - Chemical Reactions and Reaction Stoichiometry
Chapter 3, Problem 42c,d
A sample of the male sex hormone testosterone, C19H28O2, contains 3.88×1021 hydrogen atoms. (c) How many moles of testosterone does it contain? (d) What is the mass of this sample in grams?
Verified step by step guidance1
To find the number of moles of testosterone, start by determining the number of moles of hydrogen atoms. Use Avogadro's number, which is approximately 6.022 × 10^23 atoms/mol, to convert the given number of hydrogen atoms to moles: \( \text{moles of H} = \frac{3.88 \times 10^{21} \text{ H atoms}}{6.022 \times 10^{23} \text{ atoms/mol}} \).
Next, calculate the number of moles of testosterone molecules. Since each molecule of testosterone (C19H28O2) contains 28 hydrogen atoms, divide the moles of hydrogen atoms by 28: \( \text{moles of testosterone} = \frac{\text{moles of H}}{28} \).
To find the mass of the testosterone sample, first calculate the molar mass of testosterone. Add the atomic masses of all the atoms in the formula C19H28O2: \( \text{Molar mass of C19H28O2} = (19 \times 12.01 \text{ g/mol}) + (28 \times 1.008 \text{ g/mol}) + (2 \times 16.00 \text{ g/mol}) \).
Once you have the molar mass, use it to convert the moles of testosterone to grams: \( \text{mass in grams} = \text{moles of testosterone} \times \text{molar mass of C19H28O2} \).
Ensure all units are consistent and check your calculations for accuracy. This will give you the mass of the testosterone sample in grams.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Avogadro's Number
Avogadro's number, approximately 6.022 × 10²³, is the number of atoms, ions, or molecules in one mole of a substance. This constant allows chemists to convert between the number of particles and the amount of substance in moles, which is essential for stoichiometric calculations in chemistry.
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Molar Mass
Molar mass is the mass of one mole of a substance, typically expressed in grams per mole (g/mol). For testosterone (C₁₉H₂₈O₂), the molar mass can be calculated by summing the atomic masses of all the atoms in its molecular formula, which is crucial for determining the mass of a sample based on the number of moles.
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Stoichiometry
Stoichiometry is the branch of chemistry that deals with the quantitative relationships between the reactants and products in a chemical reaction. It involves using balanced chemical equations to calculate the amounts of substances consumed and produced, which is fundamental for solving problems related to moles and mass in chemical samples.
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Related Practice
Textbook Question
A sample of the male sex hormone testosterone, C19H28O2, contains 3.88×1021 hydrogen atoms. (b) How many molecules of testosterone does it contain?
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