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Ch.3 - Molecules, Compounds & Chemical Equations
Chapter 3, Problem 137

Find the total number of atoms in a sample of cocaine hydrochloride, C17H22ClNO4, of mass 23.5 mg.

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Key Concepts

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

Molecular Formula

The molecular formula of a compound provides the types and numbers of atoms present in a molecule. For cocaine hydrochloride, C17H22ClNO4, the formula indicates it contains 17 carbon (C) atoms, 22 hydrogen (H) atoms, 1 chlorine (Cl) atom, 1 nitrogen (N) atom, and 4 oxygen (O) atoms. Understanding the molecular formula is essential for determining the total number of atoms in a given mass of the substance.
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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). To find the total number of atoms in a sample, one must first calculate the molar mass of cocaine hydrochloride by summing the atomic masses of all atoms in its molecular formula. This value allows for the conversion of the sample's mass into moles, which is crucial for further calculations.
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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. Once the number of moles of cocaine hydrochloride is determined from the sample's mass and its molar mass, Avogadro's number can be used to calculate the total number of individual atoms in the sample. This concept is fundamental in bridging the macroscopic and microscopic worlds in chemistry.
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