Chemistry 30

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1. Determine the oxidation number of each element in the following compounds.

Rules:

1. Pure elements have an oxidation number of 0
2. If the compound is an ionic compound, the oxidation number for each element is the ion’s charge
3. The oxidation number of hydrogen in a compound is +1
4. The oxidation number of oxygen in most compounds is –2
   (peroxides are the exception; in peroxides oxygen has an oxidation number of –1)
5. The sum of the oxidation numbers in a compound is zero.
6. The sum of the oxidation numbers in a polyatomic ion is equal to the ion charge.

	Hint	Oxidation Numbers for each Element
SnCl4	Rule 2	Sn		Cl
Ca3P2	Rule 2	Ca		P
SnO	Rules 4, 5	Sn		O
Ag2S	Rule 2	Ag		S
HI	Rule 3, 5	H		I
N2H4	Rule 3, 5	N		H
Al2O3	Rule 4, 5	Al		O
S8	Rule 1	S
HNO2	Rules 3, 4, 5	H		N		O
O2	Rule 1	O
H3O+	Rules 3, 4, 6	H		O
ClO3-	Rules 4, 6	Cl		O
S2O22-	Rules 4, 6	S		O
KMnO4	Rules 4, 5, 6	K		Mn		O
(NH4)2SO4 Rules 4, 5, 6		N		H		S		O

 

2. Determine the oxidation number of carbon in each of the following compounds:

a. methane, CH₂

b. formaldehyde, CH₂O

c. carbon monoxide, CO

d. carbon dioxide, CO₂

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