Give the oxidation number of the element indicated for each compound.

a) carbon in Na2C2O4

b) nitrogen in HNO3

c) sulfur in H2SO4

d) carbon in HCO3 -

e) manganese in KMnO4

f) chromium in Cr2O7 2-

a. C: + 3; b. N: + 5; c. S:+6; d. C: + 4; e. Mn: + 7; f. Cr: + 6.

Explanation:

Global charges in molecules is 0

You sum all the oxidation states to determine the oxidation state for the compound.

Na₂C₂O₄ → Sodium oxalate → Global charge: 0

Oxidation state for C: + 3

HNO₃ → Nitric acid → Global charge: 0

Oxidation state for N: + 5

H₂SO₄ → Sulfuric acid → Global charge: 0

Oxidation state for S: + 6

HCO₃⁻ → Bicarbonate → Global charge: - 1, this is an anion

Oxidation state for C: + 4

KMnO₄ → Potassium permanganate → Global charge: 0

Oxidation state for Mn: + 7

Cr₂O₇⁻ → Anion dichromate → Global charge: - 2

Oxidation state for Cr: + 6