Multiple Choice
Which of the following is the correct chemical formula for aluminum iodide?
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3. Chemical Reactions
Naming Ionic Compounds
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Which of the following is the correct chemical formula for chromium(III) oxide?
A
CrO3
B
CrO2
C
Cr3O2
D
Cr2O3
Verified step by step guidance1
Identify the oxidation state of chromium in chromium(III) oxide. The Roman numeral III indicates that chromium has a +3 charge, so Cr is Cr^{3+}.
Determine the charge of the oxide ion. Oxygen typically forms an oxide ion with a charge of O^{2-}.
Balance the total positive and negative charges to find the correct ratio of chromium to oxygen atoms. Set up the equation: 2 \times (+3) + 3 \times (-2) = 0, ensuring the compound is electrically neutral.
From the charge balance, deduce the empirical formula. Since 2 chromium ions (each +3) balance 3 oxide ions (each -2), the formula is Cr_{2}O_{3}.
Compare the options given with the empirical formula derived. The correct formula for chromium(III) oxide is Cr_{2}O_{3}.
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