How many sulfate ions are present in one formula unit of aluminum sulfate?

• A. 1
• B. 2
• C. 3
• D. 4

Answer: (C)

Verified step by step guidance

1. Identify the chemical formula of aluminum sulfate. Aluminum has a charge of +3 (Al³⁺), and the sulfate ion has a charge of -2 (SO₄²⁻).
2. Write the formula by balancing the total positive and negative charges so the compound is electrically neutral. This means the total positive charge from aluminum ions must balance the total negative charge from sulfate ions.
3. Set up the charge balance equation: let the number of aluminum ions be x and sulfate ions be y. Then, 3x = 2y to balance charges.
4. Since aluminum sulfate is a known compound, the formula is Al₂(SO₄)₃, meaning there are 2 aluminum ions and 3 sulfate ions per formula unit.
5. Therefore, the number of sulfate ions in one formula unit of aluminum sulfate is 3.