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Ch.3 - Molecules, Compounds & Chemical Equations
Tro - Chemistry: A Molecular Approach 4th Edition
Tro4th EditionChemistry: A Molecular ApproachISBN: 9780134112831Not the one you use?Change textbook
All textbooksTro 4th EditionCh.3 - Molecules, Compounds & Chemical EquationsProblem 67a,b,c
Chapter 3, Problem 67a,b,c

Calculate the mass (in g) of each sample. a. 5.94×1020 SO3 molecules b. 2.8×1022 H2O molecules c. 1 glucose molecule (C6H12O6)

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Identify the given quantity: 5.94 \(\times\) 10^{20} \(\text{ SO}\)_3 \(\text{ molecules}\).
Use Avogadro's number to convert molecules to moles. Avogadro's number is 6.022 \(\times\) 10^{23} \(\text{ molecules/mol}\).
Calculate the number of moles of \(\text{SO}\)_3 by dividing the number of molecules by Avogadro's number.
Determine the molar mass of \(\text{SO}\)_3. The molar mass is the sum of the atomic masses of sulfur (S) and oxygen (O) from the periodic table: \(\text{Molar mass of }\) \(\text{SO}\)_3 = \(\text{Molar mass of S}\) + 3 \(\times\) \(\text{Molar mass of O}\).
Multiply the number of moles of \(\text{SO}\)_3 by its molar mass to find the mass in grams.

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Key Concepts

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

Molecular Mass

Molecular mass is the sum of the atomic masses of all atoms in a molecule, expressed in grams per mole (g/mol). For sulfur trioxide (SO3), the molecular mass can be calculated by adding the atomic mass of sulfur (approximately 32.07 g/mol) and three times the atomic mass of oxygen (approximately 16.00 g/mol), resulting in a total molecular mass of about 80.07 g/mol.
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Atomic Mass

Avogadro's Number

Avogadro's number, approximately 6.022 x 10^23, is the number of particles (atoms, molecules, etc.) in one mole of a substance. This constant allows chemists to convert between the number of molecules and the amount of substance in moles, which is essential for calculating mass from a given number of molecules.
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Avogadro's Law

Mass Calculation from Molecules

To calculate the mass of a sample from a given number of molecules, first convert the number of molecules to moles using Avogadro's number. Then, multiply the number of moles by the molecular mass of the substance. This process provides the mass in grams, allowing for practical applications in chemistry.
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Molar Mass Calculation Example
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