Multiple Choice
Which of the following is the correct chemical formula for the ionic compound sodium chromate?
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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
CrO2
B
Cr3O2
C
Cr2O3
D
CrO3
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 the ion 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 form a neutral compound. To do this, find the smallest whole number ratio of Cr^{3+} and O^{2-} ions such that the total positive charge equals the total negative charge.
Set up the charge balance equation: 3x (number of Cr^{3+} ions) = 2y (number of O^{2-} ions). The smallest whole numbers satisfying this are x=2 and y=3, giving 2 Cr^{3+} ions and 3 O^{2-} ions.
Write the chemical formula using the ratio found: Cr_{2}O_{3}. This is the correct formula for chromium(III) oxide.
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