Calculating the Molar Mass of Calcium Bromide

Oct 13, 2025 by magicalceylontours.com 99 views

In this problem, we are tasked with finding the mass in grams of 0.442 moles of calcium bromide, denoted as $CaBr_2$ . To solve this, we need to understand the concept of molar mass and how to calculate it.

What is Molar Mass?

Molar mass is the mass of one mole of a substance. It is calculated by adding the atomic masses of all the atoms in a molecule. In the case of calcium bromide, the atomic mass of calcium ( $Ca$ ) is 40.1 g/mol, and the atomic mass of bromine ( $Br$ ) is 79.9 g/mol.

Calculating the Molar Mass of Calcium Bromide

To calculate the molar mass of calcium bromide, we need to add the atomic masses of calcium and two bromine atoms.

Molar mass of $CaBr_2$ = Atomic mass of $Ca$ + 2 x Atomic mass of $Br$ = 40.1 g/mol + 2 x 79.9 g/mol = 40.1 g/mol + 159.8 g/mol = 199.9 g/mol

Calculating the Mass of 0.442 Moles of Calcium Bromide

Now that we have the molar mass of calcium bromide, we can calculate the mass of 0.442 moles of the substance.

Mass of $CaBr_2$ = Number of moles x Molar mass = 0.442 mol x 199.9 g/mol = 88.4 g

Conclusion

Therefore, the mass in grams of 0.442 moles of calcium bromide is 88.4 g.

Answer

The correct answer is B. 88.4 g.

Additional Information

To verify our answer, we can calculate the mass of calcium bromide using the atomic masses of calcium and bromine.

Mass of $Ca$ = Number of moles x Atomic mass = 0.442 mol x 40.1 g/mol = 17.7 g

Mass of $Br$ = 2 x Number of moles x Atomic mass = 2 x 0.442 mol x 79.9 g/mol = 70.7 g

Total mass of $CaBr_2$ = Mass of $Ca$ + Mass of $Br$ = 17.7 g + 70.7 g = 88.4 g

As we can see, our answer is consistent with the calculation using the atomic masses of calcium and bromine.

References

CRC Handbook of Chemistry and Physics, 97th Edition
IUPAC Compendium of Chemical Terminology, 2nd Edition
Q&A: Understanding Molar Mass and Calculating the Mass of Substances ====================================================================

In the previous article, we discussed how to calculate the mass of a substance using its molar mass. In this article, we will answer some frequently asked questions related to molar mass and calculating the mass of substances.

Q: What is the difference between atomic mass and molar mass?

A: Atomic mass is the mass of a single atom of an element, while molar mass is the mass of one mole of a substance. Molar mass is calculated by adding the atomic masses of all the atoms in a molecule.

Q: How do I calculate the molar mass of a substance?

A: To calculate the molar mass of a substance, you need to add the atomic masses of all the atoms in a molecule. For example, the molar mass of water ( $H_2O$ ) is calculated as follows:

Molar mass of $H_2O$ = Atomic mass of $H$ + 2 x Atomic mass of $O$ = 1.0 g/mol + 2 x 16.0 g/mol = 1.0 g/mol + 32.0 g/mol = 33.0 g/mol

Q: How do I calculate the mass of a substance using its molar mass?

A: To calculate the mass of a substance using its molar mass, you need to multiply the number of moles of the substance by its molar mass. For example, if you have 0.5 moles of water and you want to calculate its mass, you can use the following formula:

Mass of $H_2O$ = Number of moles x Molar mass = 0.5 mol x 33.0 g/mol = 16.5 g

Q: What is the significance of molar mass in chemistry?

A: Molar mass is a fundamental concept in chemistry that helps us understand the properties and behavior of substances. It is used to calculate the mass of a substance, which is essential in various chemical reactions and processes.

Q: How do I convert between moles and mass?

A: To convert between moles and mass, you can use the following formula:

Mass = Number of moles x Molar mass

For example, if you have 0.5 moles of water and you want to calculate its mass, you can use the following formula:

Mass of $H_2O$ = 0.5 mol x 33.0 g/mol = 16.5 g

Q: What are some common mistakes to avoid when calculating molar mass?

A: Some common mistakes to avoid when calculating molar mass include:

Forgetting to add the atomic masses of all the atoms in a molecule
Using the wrong atomic masses for the elements
Not converting between moles and mass correctly
Not checking the units of the molar mass and the number of moles

Q: How do I verify my calculations for molar mass?

A: To verify your calculations for molar mass, you can use the following methods:

Check the units of the molar mass and the number of moles
Use a calculator or a spreadsheet to perform the calculations
Compare your answer with the expected answer
Check the atomic masses of the elements used in the calculation

Conclusion

In this article, we have answered some frequently asked questions related to molar mass and calculating the mass of substances. We have discussed the significance of molar mass in chemistry, how to calculate it, and how to convert between moles and mass. We have also provided some tips on how to verify your calculations for molar mass.