Oxidation state of no

The following are some common oxidants or reductants. Changes of oxidation states in redox reactions of the key elements are given in groups. You should justify the assigned oxidation state to your satisfaction as you read on.

• What is the oxidation state of Mo in MoO42-?

Skill:
Note that (+6) + 4*(-2) = -2, the charge of the ion MoO42-. An oxidation state is a signed number, in this case +6.

• What is the oxidation state of S in SO32-?

Discussion:
Even though S is in group VIA: O, S, Se, Te, Po, the sulfur in sulfite ions has an oxidation number +4.

• What is the oxidation state of As in AsO43-?

Discussion:
This is the normal oxidation state of group VA: N, P, As, Sb, Bi.

• What is the oxidation state of Br in BrO3-?

Discussion:
Br has many oxidation states, e.g. +7 in BrO4-.

• What is the oxidation state of As in As2S3?

Discussion:
The oxidation for S is -2, since it is in the group VIA: O, S, Se, Te, Po. Super! S being in the same group as O, has an oxidation state of -2.

• What is the oxidation state of Cr in Cr(OH)3?

Discussion:
There are three OH- groups in the compound. Chromium hydroxide, Cr(OH)3, is a greenish gelatinous solid.