1 / 12

Electrolytic cells

ELECTROLYSIS AND ELECTROLYTIC CELLS [NON spontaneous cells] Purpose: To produce purified forms of elements . Electrolytic cells. Nonspontaneous Usually one cell Two of the same electrodes (graphite is a good choice) Must have a power source Use energy to create a chemical change.

sibyl
Download Presentation

Electrolytic cells

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. ELECTROLYSIS AND ELECTROLYTIC CELLS[NON spontaneous cells]Purpose: To produce purified forms of elements

  2. Electrolytic cells Nonspontaneous Usually one cell Two of the same electrodes (graphite is a good choice) Must have a power source Use energy to create a chemical change

  3. Voltaic cells are spontaneous Separated into two cells Is a battery Anode is negative Cathode is positive AnOx Red Cat Fat Cat Electrolytic cells are forced to work by using a power source Single container NEEDS a battery Anode is positive Cathode is negative AnOx Red Cat Fat Cat EPA (electrolytic positive anode)

  4. If there is no water present and you have a pure molten ionic compound, then… The cation will be reduced (gain electrons/go down in charge). The anion will be oxidized (lose electrons/go up in charge).

  5. Diagram an electrolytic cell of a molten solution of KI. Be sure to include anode, cathode, and overall cell reactions. Clearly state any observations and label electron flow.

  6. To predict products in aqueous solutions: • No IA or IIA metal will ever be oxidized • No polyatomic ion will ever oxidize Instead– use water Memorize these equations: Oxidation 2H2O  O2 + 4H+ + 4e- Reduction 2H2O + 2e-  H2 + 2OH-

  7. If water is present and you have an aqueous solution of the ionic compound, then… You’ll need to figure out if the ions are reacting, or the water is reacting. You can always look at a reduction potential table to figure it out.

  8. Faraday’s Law • The amount of substance being oxidized or reduced at each electrode during electrolysis is directly proportional to the amount of electricity that passes through the cell. • Use dimensional analysis • #coulombs= It I is current (ampheres) (q) q is charge (coulombs), t = time Conversions given: • 1 volt = 1 Joule/Coulomb • 1 Amp = 1 Coulomb/second (current) • Faraday = 96,500 Coulombs/mole of e- • mole of e- come from balanced redox equation

  9. Free Energy G = -nFE G = Gibb’s Free Energy [Reaction is spontaneous if ΔGis negative] n = number of mole of electrons F = 96,500 coulomb/mol e- E = cell potential 1 volt = Joule/coulomb

  10. Summary of Gibb’s Free Energy and Cells • -Eo implies NONspontaneous • +Eo implies spontaneous (would be a good battery!) • E = 0, equilibrium reached (dead battery) • the larger the voltage, the more spontaneous the reaction • G will be negative in spontaneous reactions • K>1 are favored

  11. Two important equations G = - nFE [“minus nunfe”] G = - RTlnK [“ratlink”] G = Gibbs free energy n = number of moles of electrons. F = Faraday constant 9.6485309 x 104 J/V (1 mol of electrons carries 96,500C ) E = cell potential R = 8.31 J/molK T = Kelvin temperature K = equilibrium constant [products]coeff/[reactants]coeff

  12. Favored conditions Ecell > 0 G < 0 K>1

More Related