University:
York University
Course:
CHEM 1001 | Chemical Dynamics
Academic year:

2022
Views:

305

Pages:

3
Author:

Niklas

Chapter 11 04/15/2022 04/18/2022 •For every 59/n mV of potential corresponds to one decade of key E (0.05916) 108 When the concentration increases, Ecell > E^o -lowers Q - favors formation of products (Le Chatelier) reaction becomes more spontaneous, so Ecell increases Ecell (Standard) -gases at 1 atm -solutions at 1.0M concentration -liquids & solids as pure substances Calculating Ecell under non-standard conditions -ΔG: ΔG = ΔG° + RT lnQ -Ecell: Ecell = E° - (0.05916/n) logQ Oxidizing agent ne = reducing agent - more positive redox couple is "ox" Concentration cells -if same redox couple on both sides under standard conditions, Ecell = 0 -current will flow until the two concentrations are equal •entropy driven •Membrane Potentials -inside cells, [K+]inside > [K+]outside but the concentration wants to equalize [Na+]inside < [Na+]outside -cell membranes allow gated cation transport but not anion transport -charge imbalance creates an electrical potential difference similar to a galvanic cell (Na+ salt bridge) Nerve impulses Chapter 11 04/18/2022 04/20/2022 Nerve impulses - time course of the action potential Na permeability K permeability Action potential propagates along a nerve fiber by opening nearby Na+ channels induced hyperpolarization steps signals from propagating backward another signal can be sent 3 ms later •using cell potentials to measure equilibrium constants -use half-cell potentials -kap: 10^-5 Electrochemical disproportionation reactions multi-electron redox potentials -add up ΔG°'s and divide by n (ΔG° = -nFE) -E°cell = (ΔG° / nF) = (Σn_iΔG°_i / nF) Primary Batteries made from pairs of redox couples that differ by 1-2V or more -non-rechargeable =) must be inexpensive, safe, stable Dry cell •Anode: Zn(s) → Zn2+(aq) + 2e- •Cathode: 2NH4Cl + 2MnO2(s) + 2e- → Mn2O3(s) + 2H2O + 2NH3(aq) Daniell Cell •Anode: Zn(s) → Zn2+(aq) + 2e- •Cathode: Cu2+(aq) + 2e- → Cu(s) Chapter 11 04/10/2022 04/21/2022 Secondary Batteries - rechargeable batteries - electrochemically reversible anode & cathode -Lead Acid Battery Anode: Pb(s) + SO4^2- → PbSO4(s) + 2e- Cathode: PbO2(s) + SO4^2- + 4H+ + 2e- → PbSO4(s) + 2H2O Overall: Pb(s) + PbO2(s) + 2H2SO4 → 2PbSO4(s) + 2H2O -Rechargeable Nickel-Metal Hydride Battery Anode: rare earth alloy M(s) + H2O + e- → MH(s) + OH-(aq) - M = rare earth - Ni - Co alloy (LaNi5, CoSi2, LaNi4.5Co0.7Si) Cathode: NiO(OH)(s) + H2O + e- → Ni(OH)2(s) + OH-(aq) Overall: NiO(OH)(s) + MH(s) → Ni(OH)2(s) + M(s)