Multiple Choice
Which of the following is the correct chemical formula for calcium oxide?
3. Chemical Reactions
Naming Ionic Compounds
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Which of the following is the correct chemical formula for chromium(III) sulfide?
A
Cr3S2
B
CrS3
C
CrS
D
Cr2S3
Verified step by step guidance1
Identify the oxidation state of chromium in chromium(III) sulfide. The (III) indicates that chromium has a +3 charge, so Cr is Cr^{3+}.
Determine the charge of the sulfide ion. Sulfide (S) typically has a charge of -2, so S is S^{2-}.
Balance the total positive and negative charges to find the ratio of chromium to sulfide ions. Let the number of Cr^{3+} ions be x and the number of S^{2-} ions be y. The total charge must be zero: 3x + (-2)y = 0.
Solve the equation 3x = 2y to find the smallest whole number ratio. This gives x = 2 and y = 3, meaning 2 chromium ions and 3 sulfide ions combine.
Write the chemical formula using the ratio found: Cr_{2}S_{3}.
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