Question

question 9

what is the molar mass of aluminum sulfate?

123.0 g/mol
342.2 g/mol
306.2 g/mol
315.2 g/mol
278.0 g/mol

Explanation:

🆕 New Concept Discovered: Molar Mass of Compounds
Finding the total mass of a chemical formula

Step 1: Determine the chemical formula

Aluminum forms a \( \text{Al}^{3+} \) cation, and sulfate is a polyatomic anion with the formula \( \text{SO}_4^{2-} \).

To balance the charges to make a neutral compound, we need two aluminum ions for every three sulfate ions:

$$ \text{Al}_2(\text{SO}_4)_3 $$

Step 2: List the atomic masses of each element

Using the periodic table, we find the average atomic mass for each element:

• Aluminum (\( \text{Al} \)): \( 26.98 \text{ g/mol} \)
• Sulfur (\( \text{S} \multi-line \)): \( 32.06 \text{ g/mol} \)
• Oxygen (\( \text{O} \)): \( 16.00 \text{ g/mol} \)

Step 3: Calculate the total mass

Multiply the atomic mass of each element by the number of times it appears in the formula \( \text{Al}_2(\text{SO}_4)_3 \):

• Aluminum (\( \text{Al} \)):

$$ 2 \times 26.98 \text{ g/mol} = 53.96 \text{ g/mol} $$

• Sulfur (\( \text{S} \)):

$$ 3 \times 32.06 \text{ g/mol} = 96.18 \text{ g/mol} $$

• Oxygen (\( \text{O} \)):

$$ 12 \times 16.00 \text{ g/mol} = 192.00 \text{ g/mol} $$

Sum these values to find the total molar mass:

$$ 53.96 + 96.18 + 192.00 = 342.14 \text{ g/mol} $$

This rounds to \( 342.2 \text{ g/mol} \).

Answer:

\( 342.2 \text{ g/mol} \)