University College - Chemistry Chem 112A Lecture Notes - Lecture 10: Nernst Equation, Electrochemistry, Lead
4 Apr 2016
School
Department
Professor
Document Summary
Deltag^o_cathode = deltag^o_f(h2o) + 1/2deltag^o_f(h2) - deltag^o_f(h3o+) - = -237. 18 kj/mol + 1/2o + 237. 18kj/mol - deltag^o_f(e-) Deltae_cell = deltae^o_cell - rt/(n_ef)ln([anode]/[cathode]) -> nernst equation. Pb^2+ + 2e- -> pb e_red = -. 1203v. Pbso4 + 2 e- -> pb + so4^2- e_red = -. 356. = 44. 33 kj/mol k_sp(pbso4) = e^(-44330/8. 314/298) = 1. 7 * 10^(-8) Categorizing galvanic cells = primary and secondary cells. Anode: zn -> zn^2+ + 2 e- e_red = -0. 76. Cathode: 2mno2 + 2nh4+ + 2e- -> mn2o3 + 2nh3 + h2o e_red = +0. 75v. Overall: zn + 2 mno2 + nh4+ -> zn^2+ + mn2o3 + 2nh3 + h2o. Deltae_cell = e_red (cathode) - e_red (anode) = 1. 51v. Deltae_cell = deltae_all - rt/n/f ln(azn^2+ * (anh3)^2/a(nh4+)^2) Anode: 2oh- + zn -> zn(oh)2 + 2 e- e_red = -0. 76v. Cathode: 2mno2 + h2o + 2e- -> mn2o3 + 2oh- e_red = +0. 75v. 2 mno2 + h2o + zn -> zn(oh)2 + mn2o3 deltae_cell = 1. 51v.
