S4O62-(aq) + Cr2+(aq) Cr3+(aq) + S2O32-(aq) → The appropriate half-reactions are S4O62- + 2 e- 2 S2O32- E° = 0.17V (1) → Cr3+ + e- Cr2+ E° = -0.50 V (2) → Balance the redox reaction, and calculate and (at 25°C). E° K E° = 0.67 V = 1022.6 = 4 × 1022 K Applications of Galvanic Cells Batteries: cells connected in series; potentials add together to give a total voltage. Examples: Lead-storage batteries (car)--Pb anode, PbO2 cathode, H2SO4 electrolyte Dry cell batteries Acid versions: Zn C cathode; MnO2 and NH4Cl paste Alkaline versions: some type of basic paste, ex. KOH Nickel-cadmium anode and cathode can be recharged – Fuel Reactants continuously supplied (spacecraft and oxygen) –hydrogen ELECTROLYSIS AND ELECTROLYTIC CELLS the use of electricity to about chemical change. Literal translation with Electrolysis- “split electricity” Electrolytic cells [NON spontaneous cells]: Used to separate ores or plate out metals. Important differences between a voltaic/galvanic cell and an electrolytic cell: 1) Voltaic cells are spontaneous and electrolytic cells are forced to occur by using an electron pump or battery or any DC source. 2) A voltaic cell is separated into two half cells to generate electricity; an electrolytic cell occurs in a single container. 3) A voltaic [or galvanic] cell IS a battery, an electrolytic cell NEEDS a battery 4) AN OX and RED CAT still apply BUT the polarity of the electrodes is reversed. The cathode is Negative and the anode is Positive (remember Electrons E.P.A electrolytic positive anode). – still flow FATCAT. Usually use inert electrodes
S4O62-(aq) + Cr2+(aq) → Cr3+(aq) + S2O32-(aq) The appropriate half-reactions are S4O62- + 2 e- → 2 S2O32- E° = 0.17V (1) Cr3+ + e- → Cr2+ E° = -0.50 V (2) Balance the redox reaction, and calculate E° and K (at 25°C). E° = 0.67 V K = 1022.6 = 4 × 1022 Applications of Galvanic Cells Batteries: cells connected in series; potentials add together to give a total voltage. Examples: Lead-storage batteries (car)--Pb anode, PbO2 cathode, H2SO4 electrolyte Dry cell batteries Acid versions: Zn C cathode; MnO2 and NH4Cl paste Alkaline versions: some type of basic paste, ex. KOH Nickel-cadmium – anode and cathode can be recharged Fuel Reactants continuously supplied (spacecraft –hydrogen and oxygen) ELECTROLYSIS AND ELECTROLYTIC CELLS Electrolysis- the use of electricity to about chemical change. Literal translation “split with electricity” Electrolytic cells [NON spontaneous cells]: Used to separate ores or plate out metals. Important differences between a voltaic/galvanic cell and an electrolytic cell: 1) Voltaic cells are spontaneous and electrolytic cells are forced to occur by using an electron pump or battery or any DC source. 2) A voltaic cell is separated into two half cells to generate electricity; an electrolytic cell occurs in a single container. 3) A voltaic [or galvanic] cell IS a battery, an electrolytic cell NEEDS a battery 4) AN OX and RED CAT still apply BUT the polarity of the electrodes is reversed. The cathode is Negative and the anode is Positive (remember E.P.A – electrolytic positive anode). Electrons still flow FATCAT. Usually use inert electrodes