How to Calculate Molar Mass of Aluminum - Step by Step

How to Calculate Molar Mass of Aluminum


How to Calculate Molar Mass of Aluminum

Aluminum is also written as aluminium (United Kingdom). It forms about 8.2% of the earth’s crust, making it the most abundant metal. It is also the most utilized nonferrous metal. Its high reactivity prevents it from occurring in its metallic form.

Aluminum is found in compounds in all surroundings, such as rocks, animals, and vegetation. Students in the chemistry world interact with the metal in labs. That is why knowing how to calculate the Al molar mass is essential.

Properties of Aluminum

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Atomic number


Atomic mass


State at room temperature


Melting point

1221oF (660oC)

Boiling point

4566oF (2519oC)


2.7 g/cm3

What is Aluminum Molar Mass?

The molar mass of aluminum refers to the mass in grams of one mole of aluminum. If you check the periodic table, the molar mass of Al is 26.982 grams per mole (26.982g/mol).

How Do We Calculate the Aluminum Molar Mass?

Molar mass = atomic mass (M = Ar) or Molar mass = Atomic mass x 1 g/mol

  1. Get a periodic table and check the atomic mass of aluminum.
  2. It’s the number at the bottom of the Al abbreviation. Some tables will have the number up to two decimal places. Others will have three decimal places.
  3. Write the number down and use the formula molar mass = atomic mass (M = Ar) to find the molar mass of Al. The aluminum atomic mass, Ar (Al) = 26.982 amu. Therefore M (Al) = 26.982 g/mol
  4. Another way is multiplying the atomic mass by the molar mass constant, 1 g/mol.

M (Al) = 26.982 x 1 g/mol = 26.982 g/mol

If you would like help understanding more about this concept, we offer chemistry homework help to learners. Hire our expert service to guide you in such matters.

How Do We Get the Aluminum Molar Mass?

To arrive at 26.982 g/mol, we must return to the concept of moles in your general chemistry class. One mole of aluminum has 6.022 x 1023 Al atoms. That large number is the Avogadro’s constant. It dictates the number of units in one mole of any substance.

The mass of 6.022 x 1023 atoms of Al is also the Al atomic mass. One atom of Al has 13 protons, hence the atomic number 13. A stable isotope of aluminum has 14 neutrons. 13 protons and 14 neutrons will give you a total number of 27.

That is why you see aluminum written as 27Al, representing the element in its stable state of matter. So, it’s okay to estimate the mass of Aluminum to be 27 grams per mole.

The scientific method of identifying variations shows that aluminum has radioactive isotopes. They have various neutrons, and the most common one is 26Al. That means it has 13 protons and 13 neutrons. The mass of protons and neutrons is approximately the same, while that of the electrons is negligible.

26Al, among other isotopes, makes the mass drop by a small margin after calculation. That is why we get 26.982 as the Al molar mass, and that is what you see on the periodic table. We can round it off to 27, which is essential if you want to ease the calculations.

Tip: The molar mass of al is 26.892 g/mol. That means the atomic mass of aluminum is 26.982 amu. That also implies that one mole of aluminum (6.022 x 1023 atoms) is 26.982 grams.

5 Steps to Calculate the Molar Mass of Aluminum Compounds

Since aluminum is a highly reactive element, it exists in compounds. Below are five steps you need when calculating the molar mass of Al compounds.

We will use three examples of aluminum compounds to help you understand the steps better. We will find the molar mass of Al2O3 (Aluminum oxide), Al2S3 (aluminum sulfide), and AlN (aluminum nitride).

1. Identify the Aluminum Material

The first step is to note the aluminum compound under study. In our case, it's aluminum oxide, aluminum sulfide, and aluminum nitride.

2. Write Down the Chemical Formula

After identifying the material, write down its chemical formula. Writing down the formula should be as easy as knowing what chemistry is. The chemical symbol of aluminum oxide is Al2O3, aluminum sulfide is Al2S3, whereas aluminum nitride is AlN.

3. List All the Elements

The third step is to list the elements in the compound. Let’s use our examples: Al2O3, Al2S3, and AlN.

  • The elements in Al2O3 are Al (aluminum) and O (oxygen).
  • The elements in Al2S3 are Al (aluminum) and S (Sulphur).
  • The elements in AlN are Al (aluminum) and N (Nitrogen)

4. Note the Atomic Mass of Each Element

Once you know the compound's elements, you find their atomic mass using the periodic table.

In our examples, we want to know the atomic mass of Al, N, S, and O.

  • The atomic mass of aluminum, Al, is 26.98
  • Nitrogen, N, has an atomic mass of 14.01
  • Oxygen, O, has an atomic mass of 15.99
  • The atomic mass of sulfur, S, is 32.06.

5. Add the Atomic Mass of All the Elements

The last step is to add the atomic mass of all the elements of the compound. As you add, take care of the subscripts. They indicate the number of atoms and molecules in a substance.

For instance, you can see the subscripts in Al2O3 and Al2S3. The subscripts are "2" and "3” in both compounds. That indicates two aluminum atoms and three oxygen and sulfur atoms in each combination.

So, when determining the molar mass of compounds (or molecules) with a subscript, multiply the atomic mass of elements with the element’s subscript. For instance:

Al2O3 molar mass = (atomic mass of 2 Al atoms) + (atomic mass of 3 O atoms)

That translates to:

= 2(atomic mass of Al) + 3(atomic mass of O)

= (2 x 26.98) + (3 x 15.99)

= 101.93 g/mol

The molar mass of Al2S3 = (atomic mass of 2 Al atoms) + (atomic mass of 3 S atoms).

It is the same as saying:

                                    = 2(atomic mass of Al atom) + 3(atomic mass of S atom)

                                    = (2 x 26.98) + (3 x 32.06)

                                    = 150.14 g/mol

Calculating the molar mass of AlN is simple, as there are no subscripts. There is only one atom for both elements.

The molar mass of AlN = atomic mass of one Al atom + atomic mass of one N atom

= 26.98 + 14.01

= 40.99 g/mol

We can help you with molar mass calculations and their applications, too. Hire our chemistry help service and get the fitting assignment assistance.

Why Is It Important to Calculate the Molar Mass of Aluminum?

Calculating the aluminum molar mass is essential for several reasons:

  • Stoichiometry in chemical reactions: The molar mass of alum is crucial for understanding the quantitative aspects of the chemical reactions. It is used to convert between the mass of a substance and the number of moles. That enables precise calculations of reactants and products in chemical equations involving this metal.
  • Determining the number of moles: The al molar mass helps us to determine the number of moles of a substance. If you divide the mass of the given sample by its molar mass, you get the moles.
  • Formulating and analyzing compounds: For aluminum compounds, the molar mass is the sum of the molar masses of individual elements in the combination. This information is vital for understanding and formulating the chemical bonding of the compounds.
  • Quality control in industries: In industries where aluminum is utilized, calculating the molar mass is crucial. It ensures that the right amounts of materials are used in processes, preventing waste and ensuring product consistency.
  • Research and Experimentation: Researchers often need accurate molar mass values for their experiments and studies. Calculating molar mass is vital in determining reaction yields or studying the behavior of aluminum in various conditions.

Properties of Aluminum

Aluminum has interesting physical and chemical properties. It has many applications in industries, as depicted in the next section. Here is an overview of those properties.

What are the Physical Properties of Aluminum?

  • Density: The density of aluminum is approximately 2.70 grams per cubic centimeter (g/cm³). This relatively low density contributes to its lightweight nature.
  • Melting point: Aluminum has a melting point of about 660oC (1221oF). This relatively low melting point is advantageous for various manufacturing processes.
  • Boiling point: Its boiling point is around 2519oC (4566oF).
  • Appearance: It’s a silvery-white metal with a distinctive luster.
  • Crystal structure: The structure of aluminum is a face-centered cubic crystal.
  • Electrical conductivity: The metal is a good conductor of electricity. It has approximately 61% of the electrical conductivity of copper. That is why it’s suitable for electrical applications.
  • Thermal conductivity: Aluminum also has good thermal conductivity, allowing it to conduct heat efficiently. This property is valuable in applications like heat exchangers.
  • Coefficient of linear expansion: This metal has a relatively high coefficient of linear expansion. That means it expands significantly with temperature increases. This property is vital to consider in applications where dimensional stability is critical.
  • Hardness: Pure aluminum is relatively soft. Its hardness is increased by alloying it with other elements.
  • Tensile strength: Its tensile strength can vary depending on the alloy and the treatment it undergoes. It is generally lower than that of steel. However, aluminum alloys can be designed for specific strength requirements.
  • Ductility and malleability: Aluminum is highly ductile and malleable, which can be stretched and formed into various shapes without breaking.

These physical properties contribute to the versatility of aluminum. That is why it is suitable for various applications across different industries.

What Are the Chemical Properties of Aluminum?

The chemical properties of aluminum include its reactions with other elements and compounds. You can check our types of chemical reactions worksheet to learn more about the different kinds. The crucial ones for aluminum include:

  • Corrosion resistance: Aluminum is highly resistant to corrosion. It has a thin, protective oxide layer on its surface. This oxide layer prevents further corrosion and contributes to the metal's durability.
  • Reaction with oxygen: Aluminum readily reacts with oxygen in the air to form aluminum oxide (Al2O3). The oxide layer prevents further oxidation: 4Al+3O2 → 2Al2O3
  • Reaction with acids: Aluminum reacts with strong acids, such as hydrochloric acid (HCl) or sulfuric acid (H₂SO₄), to produce aluminum salts and hydrogen gas: 2Al+6HCl→2AlCl3+3H2
  • Reaction with bases: In the presence of strong bases, like sodium hydroxide (NaOH), aluminum reacts to form aluminum hydroxide and hydrogen gas: 2Al+6NaOH+6H2O → 2Na3Al(OH)6+3H2
  • Reaction with halogens: Aluminum reacts with halogens (fluorine, chlorine, bromine, iodine) to form aluminum halides. The equation below shows the reaction between aluminum and chlorine to form aluminum chloride: 2Al+3Cl2→2AlCl3
  • Reaction with water: Under normal conditions, aluminum is relatively inert to water because of the protective oxide layer. However, if the oxide layer is damaged or aluminum powder is used, it can react with water to produce aluminum hydroxide and hydrogen gas: 2Al+6H2​O → 2Al(OH)3​+3H2​
  • Reaction with nitric acid: Aluminum reacts with nitric acid (HNO₃) to produce aluminum nitrate, nitrogen dioxide gas, and water: 6Al+8HNO3 ​→ 6Al(NO3​)3​+3H2​O+4NO2

Understanding these chemical properties helps predict how aluminum will behave in various environments and chemical reactions.

What Are The Uses of Aluminum?

Aluminum is used in myriads of products. Some include kitchen utensils, foils, cans, beer kegs, window frames, and airplane parts. Its unique qualities make it a good candidate for these products and others.

Most of the time, aluminum is utilized as an alloy because it is not strong enough. You readily find aluminum alloys with silicon, magnesium, manganese, and copper.

Frequently Asked Questions

1. What is the mass of one mole of aluminum?

The atomic mass of aluminum (Al) is 26.981539 u. In other words, one mole of aluminum has a mass of 26.981539 g.

2. What is the molar mass of aluminum?

The Aluminum molar mass is 26.98 g/mol. It is also the same as its atomic mass.

3. What is the molar mass of aluminum sulfate?

The aluminum sulfate molar mass is 342.15 g/mol.

4. What is the molecular mass of aluminum chloride?

Aluminum chloride molar mass is 133.332 u.

5. What is the molar mass of aluminum nitrate?

The molar mass of aluminum nitrate is 212.996 g/mol.

Bottom Line

Calculating the molar mass of aluminum is now easy if you follow the steps we have provided. Ensure that you have a periodic table when calculating the Al molar mass.

The steps we have provided can also be used to calculate the molar mass of any other element or compound. If you have any challenges with such calculations or their applications, we are available to help. You can contact our chemistry experts anytime and let them relieve your stress.

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