Calculating the Mass of Aluminum Sulfate

Oct 13, 2025 by wbrum.org 62 views

The Aluminum Sulfate Hydrate: Calculating the Number of Water Molecules

Aluminum sulfate hydrate, denoted as ${$ Al_2(SO_4)_3 \times xH_2O]$, is a chemical compound that contains aluminum, sulfur, and oxygen atoms. The presence of water molecules in the compound is denoted by the variable [ $x\$}$ , which represents the number of water molecules associated with each ${$ Al_2(SO_4)_3$}$ unit. In this article, we will calculate the value of ${$ x$}$ using the given information that the compound contains 8.10 percent aluminum by mass.

To solve this problem, we need to understand the concept of molar mass and the relationship between the mass of aluminum and the mass of the entire compound. The molar mass of aluminum (Al) is 26.98 g/mol, and the molar mass of aluminum sulfate ( ${$ Al_2(SO_4)_3$}$) is 342.14 g/mol. We are given that the compound contains 8.10 percent aluminum by mass, which means that 8.10 grams of aluminum is present in 100 grams of the compound.

Calculating the Mass of Aluminum Sulfate

Let's assume that we have 100 grams of the aluminum sulfate hydrate compound. Since 8.10 grams of this compound is aluminum, the remaining 91.90 grams must be the mass of the aluminum sulfate ( ${$ Al_2(SO_4)_3$}$) and water molecules combined.

Calculating the Number of Moles of Aluminum

We can calculate the number of moles of aluminum present in 8.10 grams of the compound using the formula:

${$ n = \frac{m}{M}$}$

where ${$ n$}$ is the number of moles, ${$ m$}$ is the mass of aluminum in grams, and ${$ M$}$ is the molar mass of aluminum.

${$ n = \frac{8.10\ g}{26.98\ g/mol} = 0.300\ mol$}$

Calculating the Number of Moles of Aluminum Sulfate

We can calculate the number of moles of aluminum sulfate ( ${$ Al_2(SO_4)_3$}$) present in 91.90 grams of the compound using the formula:

${$ n = \frac{m}{M}$}$

where ${$ n$}$ is the number of moles, ${$ m$}$ is the mass of aluminum sulfate in grams, and ${$ M$}$ is the molar mass of aluminum sulfate.

${$ n = \frac{91.90\ g}{342.14\ g/mol} = 0.269\ mol$}$

Calculating the Number of Water Molecules

We can calculate the number of water molecules associated with each ${$ Al_2(SO_4)_3$}$ unit by dividing the number of moles of water by the number of moles of aluminum sulfate.

${$ x = \frac{n_{water}}{n_{Al_2(SO_4)_3}}$}$

However, we do not know the number of moles of water. To calculate the number of moles of water, we need to know the mass of water present in the compound.

Calculating the Mass of Water

We can calculate the mass of water present in the compound by subtracting the mass of aluminum sulfate from the total mass of the compound.

${$ m_{water} = m_{total} - m_{Al_2(SO_4)_3}$}$

${$ m_{water} = 100\ g - 91.90\ g = 8.10\ g$}$

Calculating the Number of Moles of Water

We can calculate the number of moles of water present in 8.10 grams of the compound using the formula:

${$ n = \frac{m}{M}$}$

where ${$ n$}$ is the number of moles, ${$ m$}$ is the mass of water in grams, and ${$ M$}$ is the molar mass of water (18.02 g/mol).

${$ n = \frac{8.10\ g}{18.02\ g/mol} = 0.450\ mol$}$

Calculating the Number of Water Molecules

Now that we know the number of moles of water, we can calculate the number of water molecules associated with each ${$ Al_2(SO_4)_3$}$ unit.

${$ x = \frac{n_{water}}{n_{Al_2(SO_4)_3}}$}$

${$ x = \frac{0.450\ mol}{0.269\ mol} = 1.67$}$

In this article, we calculated the number of water molecules associated with each ${$ Al_2(SO_4)_3$}$ unit in the aluminum sulfate hydrate compound. We used the given information that the compound contains 8.10 percent aluminum by mass and the molar masses of aluminum, aluminum sulfate, and water to solve the problem. The calculated value of ${$ x$}$ is 1.67, which means that each ${$ Al_2(SO_4)_3$}$ unit is associated with approximately 1.67 water molecules.

CRC Handbook of Chemistry and Physics, 97th Edition
IUPAC Compendium of Chemical Terminology, 2nd Edition
Chemistry: An Atoms First Approach, 2nd Edition by Steven S. Zumdahl
The Aluminum Sulfate Hydrate: Q&A

In our previous article, we calculated the number of water molecules associated with each ${$ Al_2(SO_4)_3$}$ unit in the aluminum sulfate hydrate compound. In this article, we will answer some frequently asked questions related to the aluminum sulfate hydrate and its properties.

Q: What is the chemical formula of aluminum sulfate hydrate?

A: The chemical formula of aluminum sulfate hydrate is ${$ Al_2(SO_4)_3 \times xH_2O]$, where [ $x\$}$ represents the number of water molecules associated with each ${$ Al_2(SO_4)_3$}$ unit.

Q: What is the molar mass of aluminum sulfate hydrate?

A: The molar mass of aluminum sulfate hydrate is the sum of the molar masses of aluminum sulfate ( ${$ Al_2(SO_4)_3$} $) and water molecules ($ { $x\$}$ times the molar mass of water, 18.02 g/mol).

Q: What is the percentage of aluminum in aluminum sulfate hydrate?

A: The percentage of aluminum in aluminum sulfate hydrate is 8.10 percent, which means that 8.10 grams of aluminum is present in 100 grams of the compound.

Q: How many water molecules are associated with each ${$ Al_2(SO_4)_3$}$ unit?

A: We calculated the number of water molecules associated with each ${$ Al_2(SO_4)_3$}$ unit to be approximately 1.67.

Q: What is the molar mass of aluminum?

A: The molar mass of aluminum is 26.98 g/mol.

Q: What is the molar mass of aluminum sulfate?

A: The molar mass of aluminum sulfate is 342.14 g/mol.

Q: What is the molar mass of water?

A: The molar mass of water is 18.02 g/mol.

Q: How do you calculate the number of moles of aluminum in a given mass of aluminum sulfate hydrate?

A: To calculate the number of moles of aluminum in a given mass of aluminum sulfate hydrate, you can use the formula:

${$ n = \frac{m}{M}$}$

where ${$ n$}$ is the number of moles, ${$ m$}$ is the mass of aluminum in grams, and ${$ M$}$ is the molar mass of aluminum.

Q: How do you calculate the number of moles of aluminum sulfate in a given mass of aluminum sulfate hydrate?

A: To calculate the number of moles of aluminum sulfate in a given mass of aluminum sulfate hydrate, you can use the formula:

${$ n = \frac{m}{M}$}$

where ${$ n$}$ is the number of moles, ${$ m$}$ is the mass of aluminum sulfate in grams, and ${$ M$}$ is the molar mass of aluminum sulfate.

Q: How do you calculate the number of water molecules associated with each ${$ Al_2(SO_4)_3$}$ unit?

A: To calculate the number of water molecules associated with each ${$ Al_2(SO_4)_3$}$ unit, you can use the formula:

${$ x = \frac{n_{water}}{n_{Al_2(SO_4)_3}}$}$

where ${$ x$}$ is the number of water molecules, ${$ n_{water}$}$ is the number of moles of water, and ${$ n_{Al_2(SO_4)_3}$}$ is the number of moles of aluminum sulfate.

In this article, we answered some frequently asked questions related to the aluminum sulfate hydrate and its properties. We hope that this article has provided you with a better understanding of the aluminum sulfate hydrate and its properties.

CRC Handbook of Chemistry and Physics, 97th Edition
IUPAC Compendium of Chemical Terminology, 2nd Edition
Chemistry: An Atoms First Approach, 2nd Edition by Steven S. Zumdahl