20. Electrochemistry

What is the oxidation number of each underlined element?

a) P₄                                  b) BO₃^3–                                c) AsO₄^2–                           d) HSO₄^–

In the following reaction identify the oxidizing agent and the reducing agent:

Cr₂O₇^2- + 6 Fe²⁺ + 14 H⁺ → 2 Cr³⁺ + 6 Fe³⁺ + 7 H₂O

3 Pb²+ (aq) + 2 Cr (s) → 3 Pb (s) + 2 Cr³⁺ (aq)

NO₃‾ (aq) + Cu (s) → NO (s) + Cu²⁺ (aq)

4 MnO₄^– (aq) + 12 H₃O⁺ (aq) → 4 Mn²⁺ (aq) + 5 O₂ (g) + 18 H₂O (g)

3 Pb²⁺ (aq) + 2 Cr (s) → 3 Pb (s) + 2 Cr³⁺ (aq)

Rank the given metal ions in order of increasing strength as an oxidizing agent.

Pb²⁺ (-0.13 V), Mn²⁺ (-1.18 V), Cu²⁺ (+0.16 V), Co³⁺ (+1.82 V), Fe³⁺ (+0.77 V)

Determine which species can oxidize Br₂.