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Ch.2 - Atoms, Molecules & Ions
McMurry - Chemistry 8th Edition
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Tutti i libri di testoMcMurry 8th EditionCh.2 - Atoms, Molecules & IonsProblema 9
Capitolo 2, Problema 9

How many atoms are present in 1.2 g of gold? (LO 2.16) (a) 2.5 * 1021 (b) 1.4 * 1026 (c) 7.2 * 1023 (d) 3.7 * 1021

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1
Determine the molar mass of gold (Au) from the periodic table, which is approximately 197 g/mol.
Use the formula: number of moles = mass (g) / molar mass (g/mol) to calculate the number of moles of gold in 1.2 g.
Apply Avogadro's number (6.022 x 10^23 atoms/mol) to convert the number of moles of gold to the number of atoms.
Multiply the number of moles obtained in step 2 by Avogadro's number to find the total number of atoms.
Compare the calculated number of atoms with the given options to determine the correct answer.

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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 gold (Au), the molar mass is approximately 197 g/mol. This value is essential for converting grams of a substance to moles, which is a necessary step in determining the number of atoms present in a given mass.
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Molar Mass Concept

Avogadro's Number

Avogadro's number, approximately 6.022 x 10^23, is the number of atoms, ions, or molecules in one mole of a substance. This constant allows chemists to relate the macroscopic scale of substances (grams) to the microscopic scale (number of atoms). It is crucial for calculating the total number of atoms from the number of moles.
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Avogadro's Law

Conversion from Grams to Atoms

To find the number of atoms in a given mass of a substance, one must first convert grams to moles using the molar mass, and then multiply the number of moles by Avogadro's number. This two-step conversion is fundamental in stoichiometry and allows for the quantification of atoms in a sample.
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Weight Conversion Example
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