The chemical formula of Aluminium sulphate is Al2(SO4)3. The valency of Aluminium is 3.
The Correct Answer and Explanation is:
Correct Answer:
The chemical formula of aluminum sulfate is Al₂(SO₄)₃, and the valency of aluminum is 3.
Explanation
Aluminum sulfate is a compound formed from aluminum ions and sulfate ions. To determine its correct chemical formula, a balance of charges between the participating ions is necessary. Aluminum exists as a trivalent cation, represented as Al³⁺, meaning it carries a +3 charge. Sulfate is a polyatomic anion with the formula SO₄²⁻ and carries a -2 charge.
To form a neutral compound, the total positive charge from the aluminum ions must cancel out the total negative charge from the sulfate ions. Finding the lowest common multiple of 3 (from Al³⁺) and 2 (from SO₄²⁻) gives 6. Achieving a total charge of +6 requires two aluminum ions (2 × +3 = +6), while three sulfate ions provide a total charge of -6 (3 × -2 = -6). When these ions are combined in the ratio of 2 aluminum ions to 3 sulfate ions, the resulting compound becomes electrically neutral.
Thus, the formula is written as Al₂(SO₄)₃, where the subscript “2” outside aluminum indicates two aluminum ions, and the subscript “3” outside the sulfate group (enclosed in parentheses) indicates three sulfate ions. The parentheses around SO₄ are essential, as they clarify that the subscript “3” applies to the entire sulfate group, not just to the oxygen atom.
Aluminum sulfate is commonly used in water purification, paper manufacturing, and as a mordant in dyeing processes. Its crystalline form is usually colorless or white, and it is highly soluble in water, where it dissociates into its respective ions.
Understanding the valency of elements and the charges on polyatomic ions allows for the accurate writing of chemical formulas, which are essential for stoichiometric calculations and predicting chemical behavior in reactions.
