In each of the following, tell whether the substance gains electrons or loses electrons in a redox reaction:a. An oxidizing agentb. A reducing agentc. A substance undergoing oxidationd. A substance undergoing reduction

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)