Which of the following correctly represents the chemical formula of a compound formed by aluminium and sulphate ions?
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A.
Al₃(SO₄)₂
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B.
Al(SO₄)₃
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C.
Al₂(SO₄)₃
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D.
Al₂SO₄
Correct Answer:
C. Al₂(SO₄)₃
Explanation:
To determine the chemical formula for aluminum sulfate, you must balance the charges of the aluminum cation and the sulfate polyatomic anion: - Aluminum (Al) is a group 13 metal that consistently forms a +3 charge (Al³⁺).
- Sulfate (SO₄) is a polyatomic ion with a known -2 charge (SO₄²⁻).Using the criss-cross method to achieve electrical neutrality, the magnitude of the charge on one ion becomes the subscript of the other. Thus, two aluminum ions are required to balance three sulfate ions, resulting in a total positive charge of +6 and a total negative charge of -6. Because sulfate is a polyatomic ion, it is enclosed in parentheses when more than one is present in the formula. Therefore, the correct chemical formula is Al₂(SO₄)₃.
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