Question

The molar mass of Al is 27.0 g/mol.
The molar mass of S is 32.1 g/mol.
The molar mass of O is 16.0 g/mol.
Calculate the molar mass for the compound Al2 (SO4)3

Answer 1

To calculate the molar mass of the compound Al₂(SO₄)₃, we first need to break it down into its constituent elements and their respective amounts:

1. **Aluminum (Al)**:
- There are 2 aluminum atoms.
- Molar mass of Al = 27.0 g/mol.

Contribution from Al = \(2 \times 27.0 \, \text{g/mol} = 54.0 \, \text{g/mol}\).

2. **Sulfur (S)**:
- There are 3 sulfate ions, and each sulfate ion (SO₄) contains 1 sulfur atom.
- Therefore, there are 3 sulfur atoms.
- Molar mass of S = 32.1 g/mol.

Contribution from S = \(3 \times 32.1 \, \text{g/mol} = 96.3 \, \text{g/mol}\).

3. **Oxygen (O)**:
- Each sulfate ion (SO₄) contains 4 oxygen atoms, and there are 3 sulfate ions.
- Therefore, there are \(3 \times 4 = 12\) oxygen atoms.
- Molar mass of O = 16.0 g/mol.

Contribution from O = \(12 \times 16.0 \, \text{g/mol} = 192.0 \, \text{g/mol}\).

Now, we can add up the contributions of all the elements to find the total molar mass of Al₂(SO₄)₃:

\[
\text{Total molar mass} = \text{Contribution from Al} + \text{Contribution from S} + \text{Contribution from O}
\]

\[
\text{Total molar mass} = 54.0 \, \text{g/mol} + 96.3 \, \text{g/mol} + 192.0 \, \text{g/mol} = 342.3 \, \text{g/mol}
\]

Therefore, the molar mass of Al₂(SO₄)₃ is **342.3 g/mol**.