How many molecules are in each sample? b. 389 g CBr₄

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Determine the molar mass of CBr₄ by adding the atomic masses of one carbon atom and four bromine atoms.

Calculate the number of moles of CBr₄ in the 389 g sample using the formula: \( \text{moles} = \frac{\text{mass (g)}}{\text{molar mass (g/mol)}} \).

Use Avogadro's number, \( 6.022 \times 10^{23} \text{ molecules/mol} \), to convert the moles of CBr₄ to molecules.

Multiply the number of moles by Avogadro's number to find the total number of molecules in the sample.

Ensure all units are consistent and cancel appropriately to verify the calculation process.

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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). It is calculated by summing the atomic masses of all the atoms in a molecule. For carbon tetrabromide (CBr4), the molar mass can be determined by adding the atomic mass of carbon (12.01 g/mol) to four times the atomic mass of bromine (79.90 g/mol), resulting in a total molar mass of approximately 331.73 g/mol.

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 mass of a substance and the number of molecules it contains. By using Avogadro's number, one can determine how many molecules are present in a given mass of a compound once the molar mass is known.

Mole Calculation

Mole calculation involves determining the number of moles of a substance based on its mass and molar mass. The formula used is: moles = mass (g) / molar mass (g/mol). In the case of 389 g of CBr4, you would first calculate the number of moles using its molar mass, and then multiply the result by Avogadro's number to find the total number of molecules in the sample.

How many molecules are in each sample? b. 389 g CBr4