Question

question 84 (1 point)
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the correct formulas for chromium(iii)oxide and aluminum phosphate are:

1. cr₂o₃ and alpo₄
2. cr₃o₂ and al₃po₄
3. cr₃o and al₂(po₄)₃
4. cr₃o₃ and al₃(po₄)₂

Explanation:

Step1: Analyze Chromium(III) Oxide

Chromium(III) has a charge of \( +3 \) (\( \text{Cr}^{3+} \)), and oxide is \( \text{O}^{2-} \). To balance charges, use the criss - cross method: the charge of Cr becomes the subscript of O, and vice - versa. So for \( \text{Cr}^{3+} \) and \( \text{O}^{2-} \), the formula is \( \text{Cr}_2\text{O}_3 \) (since \( 3\times2 = 2\times3 = 6 \) to balance the charges).

Step2: Analyze Aluminum Phosphate

Aluminum has a charge of \( +3 \) (\( \text{Al}^{3+} \)), and phosphate is \( \text{PO}_4^{3-} \). Using the criss - cross method, the charges are equal in magnitude (3 and 3), so the formula is \( \text{AlPO}_4 \) (since \( 3\times1=3\times1 = 3 \) to balance the charges).

Answer:

1. \( \text{Cr}_2\text{O}_3 \) and \( \text{AlPO}_4 \)