Schedule n Today 412 Chapter 11 n n

Schedule n Today (4/12): Chapter 11 n n Any questions? Monday (4/15): Chapter 21 n Start reading Chapter 21 – through at least through Section 21. 2 No office hours Monday, April 15

Electroplating Get silver metal from dissolved silver ions. To reduce silver ions, an oxidation must occur. Ag+ + e– Ag (0. 80 V) 2

Clicker Question Electrolysis of a molten salt with the formula MCl, using a current of 3. 86 amp for 16. 2 min, deposits 1. 52 g of metal. Identify the metal. a) b) c) d) e) Li Na K Rb Ca 3

Electrolysis of Water Consider the electrolysis of water in which we run a current through water to carry out the following reaction: H 2 O H 2 + ½O 2 To run a current through water we need an electrolyte. Let’s consider Na. Cl, HCl, and Na. OH. Does the choice of electrolyte affect the voltage needed to cause this reaction? If so, how. If not, why not? 4

Electrolysis of Water Assume we run a current through a 1 M solution of Na. Cl. Thus, we have H 2 O, 1 M Na+, and 1 M Cl–. Use the relevant reduction potentials to determine the reduction half-reaction and the oxidation half-reaction for the overall reaction that occurred and write each of these (3 reactions). Also determine the minimum voltage required for the reaction at 25°C. 5

Electrolysis of Water Cl 2 + 2 e– 2 Cl– 1. 36 V O 2 + 4 H+ + 4 e– 2 H 2 O 1. 23 V O 2 + 2 H 2 O + 4 e– 4 OH– 0. 40 V 2 H+ + 2 e– H 2 0. 00 V 2 H 2 O + 2 e– H 2 + 2 OH– – 0. 83 V Na+ + e– Na – 2. 71 V 6

Electrolysis of Water Instead of 1. 00 M Na. Cl as the electrolyte, suppose we use 1 M HCl. Thus, we have H 2 O, 1 M H+, and 1 M Cl–. Use the relevant standard reduction potentials to determine the reduction half-reaction and the oxidation half-reaction for the overall reaction that occurred and write each of these (3 reactions). Also determine the minimum voltage required for the reaction at 25°C. 7

Electrolysis of Water Suppose we use 1 M Na. OH as the electrolyte. Thus, we have H 2 O, 1 M Na+, and 1 M OH–. Use the relevant standard reduction potentials to determine the reduction half-reaction and the oxidation half-reaction for the overall reaction that occurred and write each of these (3 reactions). Also determine the minimum voltage required for the reaction at 25°C. 8

Clicker Question A concentration cell is constructed using two metal (M) electrodes with M 2+ concentrations of 0. 10 M and 1. 00 x 10– 5 M in the two half-cells. Determine the standard reduction potential of M 2+. a) b) c) d) e) +0. 236 V +0. 118 V – 0. 118 V 0 V It cannot be determined with the information given. 10