Multiple Choice
Which of the following half-reactions correctly represents an oxidation process?
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6. Chemical Quantities & Aqueous Reactions
Calculate Oxidation Numbers
Multiple Choice
What is the oxidation number of the sulfur atom in SO_4^{2-}?
A
+6
B
0
C
-2
D
+4
Verified step by step guidance1
Recall that the sulfate ion is \(\mathrm{SO_4^{2-}}\), which consists of one sulfur atom and four oxygen atoms, and the overall charge on the ion is \(-2\).
Assign the oxidation number of oxygen as \(-2\) because oxygen almost always has an oxidation state of \(-2\) in compounds (except in peroxides or when bonded to fluorine).
Let the oxidation number of sulfur be \(x\). Since there are four oxygen atoms, the total contribution from oxygen is \(4 \times (-2) = -8\).
Write the equation for the sum of oxidation numbers equal to the overall charge of the ion: \(x + (-8) = -2\).
Solve the equation for \(x\) to find the oxidation number of sulfur: \(x = -2 + 8\).
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