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Ch.3 - Molecules and Compounds
Chapter 3, Problem 93

How many bromine atoms are present in 12.8 g of CH2Br2?

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Calculate the molar mass of CH2Br2 by adding the atomic masses of its constituent atoms: Carbon (C), Hydrogen (H), and Bromine (Br).
Determine the number of moles of CH2Br2 in 12.8 g by using the formula: \( \text{moles} = \frac{\text{mass (g)}}{\text{molar mass (g/mol)}} \).
Recognize that each molecule of CH2Br2 contains 2 bromine atoms.
Use Avogadro's number \(6.022 \times 10^{23}\) to find the number of molecules in the calculated moles of CH2Br2.
Multiply the number of molecules by 2 (since each molecule contains 2 bromine atoms) to find the total number of bromine atoms.

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Key Concepts

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

Molar Mass

Molar mass is the mass of one mole of a substance, typically expressed in grams per mole (g/mol). For CH2Br2, the molar mass can be calculated by summing the atomic masses of its constituent elements: carbon (C), hydrogen (H), and bromine (Br). This value is essential for converting grams of a compound to moles, which is necessary for determining the number of atoms present.
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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. This constant allows chemists to relate the macroscopic scale of substances (grams) to the microscopic scale (individual atoms or molecules). In this problem, it will be used to find the total number of bromine atoms from the moles of CH2Br2.
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Stoichiometry

Stoichiometry is the calculation of reactants and products in chemical reactions based on the conservation of mass. In the context of this question, stoichiometry helps determine the ratio of bromine atoms to the moles of CH2Br2. Since each molecule of CH2Br2 contains two bromine atoms, understanding this relationship is crucial for calculating the total number of bromine atoms in the given mass.
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