Electrolysis

Chapter 17 Section 7

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Electrochemistry – Electrolytic Cells

A galvanic cell produces current spontaneous. positive cell potentialAn electrolytic cell uses energy to produce a chemical changenegative cell potential.

Forcing a current through a cellcell potential is negativeElectrical work causes a non spontaneous reaction to

occur.Practice uses - recharging batteries

producing aluminumplating to prevent corrosion

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Electrochemistry – Electrolytic Cells

Since the electrical work causes e- to flow in the opposite direction the anode and cathode are reversed.e- flow from anode to cathodeThe salt bridge ion flow is opposite in the two cells

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Galvanic Cell Electrolytic Cell

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Electrochemistry – Quantitative Electrochemistry

Stoichiometry and Electrochemistry

How much (g, mole, atoms) chemical change occurs with the flow of a given current (amps) for a specific time (seconds, minutes, hours)?

Amps = unit of charge = 1 coulomb / 1 second

1 mole of e- = the charge of a 1 faraday= 96485 coulomb / 1 mol e-The faraday is derived from the charge of an electron in coulombs and the number of e- in a mole.

The faraday connects electricity to stoichiometry.

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all about negative charge, electrons

about any charge negative or positive

1.60222 x 10-19 C

6.022 x 1023 mol • e-

Electrochemistry – Quantitative Electrochemistry

E = cell potential (volts)

Amp = 1 C / 1 sec

Volt = 1 J / 1 C

Watt = 1 J / 1 second

Volts x Amp = Watt (power)

kWh = kilowatts x hours

1kWh = 3.6 x 106 J

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Electrochemistry- Sample Page 816-817

How much copper is plated out when 10.0 amps is applied for 30 minutes to the Zn ǀ Zn2+ ǁ Cu2+ ǀ Cu cell at standard conditions?

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Electrochemistry- Sample 17.9 Page 818

How long must a current of 5.00 A be applied to a solution of Ag+ to produce 10.5 g of solid silver?

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Electrochemistry- Sample Page 819

Which would plate out first?

•Plating out for metals = reducing

•So the metal with the highest reduction potential would plate out first