“minimal” galvanic cells only need reactants Cu Cu2+(aq) + 2e-  Cu(s) o = 0.34 V a) oxidation Zn Zn2+(aq) + 2e-  Zn(s) Zn  Zn2+ + 2e-  = 0.76 V o = -0.76 V b) oxidation H+ 2H+(aq) + 2e-  H2(g) o = 0.00 V reduction 2H+ (aq) + Zn (s)  Zn2+ (aq) + H2(g) 0 = .76 V Q =  = very large

Electrolytic Cells galvanic cell electrolytic cell 2 H2(g) + O2(g)  spontaneous galvanic cell cell < 0 G > 0 non-spontaneous electrolytic cell 2 H2(g) + O2(g)  2 H2O(l) G = -474 kJ spontaneous redox reaction: H  1+ O  2-

Electrolytic Cells 2 H2O(l)  2 H2(g) + O2(g) G = 474 kJ oxygen half-cell: H2O  O2 2 H2O  O2 + 4 H+ + 4 e- a) oxidation b) reduction reaction a) anode b) cathode

Electrolytic Cells 2 H2O(l)  2 H2(g) + O2(g) G = 474 kJ hydrogen half-cell: H2O  H2 2 H2O + 2e-  H2 + OH- 2 reduction reaction cathode

Electrolytic Cells 2 H2O  O2 + 2 H2 2 H2O  O2 + 4 H+ + 4 e- anode oxidation: 2 H2O  O2 + 4 H+ + 4 e- anode 2( ) reduction: 2 H2O + 2e-  H2 + 2 OH- cathode ____________________________________ 6 H2O  O2 + 2 H2 + 4H+ + 4 OH- 2 H2O  O2 + 2 H2

Electrolysis of water - battery e- e- anode cathode oxidation + battery e- Pt electrodes e- anode cathode oxidation reduction 2H2O  O2+ 4H++ 4e- 4H2O + 4e- 2H2 + 4OH- acid base 1 mol gas 2 mol gas

Electrolysis of water 2.5 amp Power source  3.2 g O2 current = amperes (A) = coulombs/sec (C/s) current and time charge mol e- mol product gram product A(C/s) x s x 1mol e- 96,500 C x mol product mol e- x g product mol product

Electrolysis of water 2 H2O  O2 + 4 H+ + 4 e- 2.5 A, 3.2 g O2 current and time charge mol e- mol product gram product (C/s) x s x mol e- C x mol O2 mol e- mol O2 x g O2 = g O2 1 mol e- 96500 C 1 4 2.5 A 32.0 g/mol 3.2

Electrolysis of water 2 H2O  O2 + 4 H+ + 4 e- 2.5 A, 3.2 g O2 1 mol O2 x 32 g O2 4 mol e- x 1 mol O2 96500 C = 1 mol e- 38600 C 3.2 g O2 x 2.5 C x s s = 38600 C s = 15440 s 15440 s x 1 min x 60 s 1 hr 60 min = 4.3 hr

Electroplating Cu2+ + 2e-  Cu o = 0.34 V anode cathode Cu(s) oxidation reduction Cu(s)  Cu2+(aq) + 2e- Cu2+(aq) + 2e-  Cu(s) Cu2+ + 2e-  Cu o = 0.34 V

Electroplating anode cathode Cu(s)  Cu2+(aq) + 2e- reduction oxidation Cu(s)  Cu2+(aq) + 2e- Cu2+(aq) + 2e- Cu(s) 0.75 A for 25 min. deposits 0.37 g Cu atomic mass of Cu =

Electroplating Cu2+(aq) + 2e- Cu(s) 0.75 A for 25 min deposits 0.37 g Cu A (C) s x s x 1 mol e- 96500 C x 1 mol Cu 2 mol e- x g Cu mol Cu

Electroplating 0.75(C) s x 25 min x 60s min = 1.125 x 103 C x 1 mol e- 96500 C = 1.17 x 10-2 mol e- 1.17 x 10-2 mol e- x 1mol Cu 2mol e- =5.83 x 10-3mol Cu 0.37 g Cu = 63.5 g mol atomic mass Cu 5.8x10-3 mol Cu