Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Electrochemisty Galvanic or Voltaic cells o Electrolytic cells Spontaneous reaction E cell + These terms may be used in a question about galvanic/voltaic cells… Ecell ; reduction potential; oxidizing agent; reducing agent; reduction; oxidation; anode; cathode; salt bridge; electron flow; voltage; cell potential; electromotive force; galvanic/voltaic; electrode; battery; Non spontaneous reaction Eo cell These terms may be used in a question about electrolytic cells… current; amps; time; grams (mass); plate/deposit; electroplating; identity of metal; coulombs of charge Key Formulas and Relationships ANOx – oxidation at the anode Key Formulas and Relationships 96,500 Coulombs = 1 mole of electrons RedCat – reduction at the cathode molar mass = 1 mol. FATCAT – e- from the anode to the cathode # electron in eqn = # moles (use balanced overall equation for ratio) Convert all amps to # coulombs = 1 sec LEO goes GER lose e- oxidation gain ereduction “the LARGEST reduction potential gets to be reduced” # Coulombs = It or I=q/t (formula sheet) where I is amps Ecell = Eox + Ered from table 0.0592 E cell = E table log Q n=# of en Key Concepts and Important Phrases The purpose of the salt bridge is to “provide ions to keep the solutions in the cells from becoming charged” Be able to explain whether Ecell goes up or down when concentrations change. Justify using the Nernst equation relating the sign of logQ to the increase or decrease in Ecell smaller (logQ – fhappens when [ larger reactant] . [product] Label the parts of a galvanic cell: Anode; cathode; salt bridge; electron flow; half reactions; overall reaction; direction of ions from salt bridge Will the electrode be gaining mass or losing mass as that half reaction occurs? Look at equation to detemine Key Concepts and Important Phrases To predict products in an aqueous solution: Usually group IA or IIA metal will not be reduced USE WATER LAGER Eo RED is Reduced No polyatomic ion will ever oxidize USE WATER KNOW THESE: Red: 2H2O + 2e- H2 + 2OHOx: 2H2O O2 + 4H+ + 4e- Inert Pt electrodes are used in reactions from ion to ion (ie Fe3+ Fe2+) or gases Connections to Other Chapters Thermo: G = -nFE Connections to Other Chapters Stoichiometry through mole:mole ratio of coefficients and/or molar masses Assigning oxidation numbers and balancing redox reactions at equilibrium E = 0 and Q = K 0.0592 E0 log K n Potential Pitfalls and Unit warnings Watch signs on voltages --LARGEST reduction potential is used as is and the OTHER one is reversed and changed sign When balancing overall reaction make sure # of electrons is the same in both half reactions. Oxidizing agent is reduced (always a reactant – use formula as written in equation) Reducing agent is oxidized Eo cell (always a reactant – use formula as written in equation) Units on Eare volts J/coulomb Potential Pitfalls and Unit warnings Watch to make sure units cancel out in your calculations. Be careful to label moles as moles of e- or moles of A etc. to avoid confusion.