5. Classification & Balancing of Chemical Reactions

Which element is being reduced in the following reaction? 

Cr₂O₇^2- + 3 HNO₂ + 5 H⁺ → 2 Cr³⁺ +  3NO₃^- + 4 H₂O

Identify the oxidizing agent and reducing agent from the following redox reaction. 

Ba (s) + Cl₂ (g) → BaCl₂ (aq)

Which element is oxidized and which is reduced in the following reaction?

Hg (aq) + HgCl₂ (aq) → Hg₂Cl₂

Which of the following represents an oxidation-reduction reaction? 

I. PCl₃ (aq) + Cl₂ (g) → PCl₅ (aq) 

II. 2 AgNO₃ (aq) + Cu (s) → Cu(NO₃)₂ (aq) + 2 Ag (s) 

III. CO₂ (g) + 2 LiOH (aq) → Li₂CO₃ (aq) + H₂O (l)

IV. FeCl₂ (aq) + 2 NaOH (aq) → Fe(OH)₂ (aq) + 2 NaCl (aq) 

Identify the oxidized reactant, the reduced reactant, the oxidizing agent, and the reducing agent in the following reactions:

a. Fe(s) + Cu²⁺(aq) → Fe²⁺(aq) + Cu(s)

b. Mg(s) + Cl₂(g) → MgCl₂(s)

c. 2 Al(s) + Cr₂O₃(s) → 2 Cr(s) + Al₂O₃(s)

Potassium, a silvery metal, reacts with bromine, a corrosive, reddish liquid, to yield potassium bromide, a white solid. Write the balanced equation, and identify the oxidizing and reducing agents.

Identify each of the following as an oxidation or a reduction:

c. Cr³⁺(aq) + 3e^– → Cr(s)

In the mitochondria of human cells, energy is provided by the oxidation and reduction reactions of the iron ions in the cytochromes in electron transport. Identify each of the following as an oxidation or a reduction:

a. Fe³⁺ + e^– → Fe²⁺

In each of the following, tell whether the substance gains electrons or loses electrons in a redox reaction:

a. An oxidizing agent

b. A reducing agent

c. A substance undergoing oxidation

d. A substance undergoing reduction