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Ch.3 - Mass Relationships in Chemical Reactions
McMurry - Chemistry 8th Edition
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Capitolo 3, Problema 55

The 'lead' in lead pencils is actually almost pure carbon, and the mass of a period mark made by a lead pencil is about 0.0001 g. How many carbon atoms are in the period?

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Determine the molar mass of carbon. Carbon has an atomic mass of approximately 12.01 g/mol.
Calculate the number of moles of carbon in the period mark using the formula: number of moles = mass / molar mass.
Use Avogadro's number to convert the number of moles of carbon to the number of atoms. Avogadro's number is approximately \(6.022 \times 10^{23}\) atoms/mol.
Multiply the number of moles of carbon by Avogadro's number to find the total number of carbon atoms in the period mark.
Summarize the calculation to ensure all steps were followed correctly and verify the units are consistent.

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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 carbon, the molar mass is approximately 12.01 g/mol. This concept is essential for converting between the mass of a substance and the number of moles, which can then be used to find the number of atoms.
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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 (individual atoms or molecules), making it crucial for calculating the number of atoms in a given mass.
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Avogadro's Law

Stoichiometry

Stoichiometry is the area of chemistry that involves the calculation of reactants and products in chemical reactions. It uses the relationships between the quantities of substances involved, often employing molar mass and Avogadro's number to determine how many atoms or molecules are present in a given mass of a substance, such as the carbon in a period mark.
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Stoichiometry Concept
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