Oxidizing & Reducing Agents
Oxidizing Agents An oxidizing agent, or oxidant, gains electrons and is reduced in a chemical reaction. Reducing Agents A reducing agent, or reductant, loses electrons and is oxidized in a chemical reaction. Mg(s) + S(s) Mg S(s) oxidized reduced 0 0 +2 -2 Reducing Agent Oxidizing Agent
Reference Table J Strongest reducing agent – Oxidize the most Strongest oxidizing agent – Reduce the most
How to Identify Reducing and Oxidizing Agents Cl2 (aq) + 2 Br- (aq) 2 Cl- (aq) + Br2 (aq) Oxidation: 2 Br- (aq) Br2 (aq) Oxidation States:-1 0 Reduction: Cl2 (aq) 2 Cl- (aq) Oxidation States: 0 -1 * Br- loses an electron; it is oxidized from Br- to Br2.Br- is the reducing agent. * Cl2gains one electron; it is reduced from Cl2 to 2 Cl-. Cl2 is the oxidizing agent.
Learning Check: Which are the oxidizing and reducing agents? Pb + NaNO3 PbO + NaNO2 Pb loses 2e- to become Pb+2, so it is oxidized. N+5 gains 2e- to become N+3, so it is reduced. 0 +1 +5 -2 +2 -2 +1 +3 -2
Calculating Potentials Chart on p. 469 shows reduction potentials *For oxidation: reverse rxn, change the sign What is the maximum voltage that can be obtained from an electrochemical cell with Zn/Zn2+ and Cu/Cu2+? Use Table J to see which oxidizes or reduces. Zn oxidizes, Cu reduces Reduces: Cu2+ + 2e- Cu 0.34 V Oxidizes: Zn Zn2+ + 2e- 0.76 V 1.10 V ** Positive voltage = spontaneous
Learning Check: Using the table of standard potentials (p. 469), calculate the theoretical voltage. Cu/Cu2+ and Mg/Mg2+ Oxidation: Mg Mg2+ + 2e- 2.37 V Reduction: Cu2+ + 2e- Cu 0.34 V 2.7 V Mg/Mg2+ and Zn/Zn2+ Oxidation: Mg Mg2+ + 2e- 2.37 V Reduction: Zn2+ + 2e- Zn - 0.76 V 1.6 V