Determining the Number of Moles

Oct 13, 2025 by wbrum.org 110 views

Introduction

In chemistry, understanding the relationship between the number of molecules and their mass is crucial for various calculations and applications. The given problem involves finding the mass in grams of $$7.79 \times 10^{28}$$ molecules of $$NH_4$$. To solve this, we need to calculate the molar mass of $$NH_4$$, determine the number of moles, and then convert it to grams.

Calculating the Molar Mass of $$NH_4$$

The molar mass of a compound is the sum of the atomic masses of its constituent elements. In this case, $$NH_4$$ consists of one nitrogen atom and four hydrogen atoms. The atomic mass of nitrogen (N) is approximately 14.01 g/mol, and the atomic mass of hydrogen (H) is approximately 1.01 g/mol.

Molar mass of N = 14.01 g/mol
Molar mass of H = 1.01 g/mol

Calculating the Molar Mass of $$NH_4$$

To find the molar mass of $$NH_4$$, we add the molar masses of nitrogen and four times the molar mass of hydrogen.

Molar mass of NH4 = Molar mass of N + 4 * Molar mass of H
Molar mass of NH4 = 14.01 g/mol + 4 * 1.01 g/mol
Molar mass of NH4 = 14.01 g/mol + 4.04 g/mol
Molar mass of NH4 = 18.05 g/mol

Determining the Number of Moles

The number of moles of a substance can be calculated using the formula:

Number of moles = Number of molecules / Avogadro's number
Avogadro's number = 6.022 x 10^23 molecules/mol

Given that we have $$7.79 \times 10^{28}$$ molecules of $$NH_4$$, we can calculate the number of moles as follows:

Number of moles = 7.79 x 10^28 molecules / (6.022 x 10^23 molecules/mol)
Number of moles = 1.292 x 10^5 mol

Converting Moles to Grams

To convert the number of moles to grams, we multiply the number of moles by the molar mass of $$NH_4$$.

Mass in grams = Number of moles * Molar mass of NH4
Mass in grams = 1.292 x 10^5 mol * 18.05 g/mol
Mass in grams = 2.323 x 10^6 g

Conclusion

In conclusion, the mass of $$7.79 \times 10^{28}$$ molecules of $$NH_4$$ is $$2.323 \times 10^6$$ grams.

Final Answer

The final answer is: 2.323 x 10^6

Introduction

In our previous article, we explored the calculation of the mass of $$7.79 \times 10^{28}$$ molecules of $$NH_4$$. We determined that the mass of these molecules is $$2.323 \times 10^6$$ grams. In this article, we will address some frequently asked questions related to this topic.

Q: What is the significance of Avogadro's number in this calculation?

A: Avogadro's number is a fundamental constant in chemistry that represents the number of particles (atoms or molecules) in one mole of a substance. In this calculation, we used Avogadro's number to convert the number of molecules to moles. This step is crucial in determining the mass of the substance.

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

A: To calculate the molar mass of a compound, you need to add the atomic masses of its constituent elements. For example, to calculate the molar mass of $$NH_4$$, you would add the atomic mass of nitrogen (14.01 g/mol) to four times the atomic mass of hydrogen (1.01 g/mol).

Q: What is the difference between the number of molecules and the number of moles?

A: The number of molecules represents the total number of individual particles in a substance, while the number of moles represents the amount of substance in terms of the number of particles that make up one mole. In this calculation, we converted the number of molecules to moles using Avogadro's number.

Q: How do I convert moles to grams?

A: To convert moles to grams, you multiply the number of moles by the molar mass of the substance. In this calculation, we multiplied the number of moles of $$NH_4$$ by its molar mass (18.05 g/mol) to determine the mass in grams.

Q: What is the significance of scientific notation in this calculation?

A: Scientific notation is a way of expressing very large or very small numbers in a compact form. In this calculation, we used scientific notation to express the number of molecules ($$7.79 \times 10^{28}$$) and the mass in grams ($$2.323 \times 10^6$$ g). This makes it easier to work with and understand these large numbers.

Q: How do I apply this calculation to other substances?

A: To apply this calculation to other substances, you need to know the molar mass of the substance and the number of molecules. You can then use the same steps as outlined in this article to determine the mass of the substance.

Q: What are some common applications of this calculation?

A: This calculation has various applications in chemistry, such as determining the mass of a substance in a chemical reaction, calculating the amount of substance required for a reaction, and understanding the properties of a substance.

Conclusion

In conclusion, understanding the mass of $$7.79 \times 10^{28}$$ molecules of $$NH_4$$ requires a combination of knowledge of Avogadro's number, molar mass, and scientific notation. By following the steps outlined in this article, you can apply this calculation to other substances and understand the significance of this calculation in chemistry.

Final Answer

The final answer is: 2.323 x 10^6