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Page 1: Voltaic cells (Galvanic cells)€¦ · Voltaic cells (Galvanic cells) A spontaneous chemical reaction creates a potential difference which causes current to flow I I I I I II Voltmeter

PbO2 + Pb + 2H2SO4 2PbSO4 + 2H2O

Discharge cycle

Chemical energy Electrical energy

Electrical energy Chemical energy

oxidation reduction

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Cellular phone

Laptop battery

Car battery

Household batteries

Battery usesVoltaic cells (Galvanic cells)A spontaneous chemical reaction creates a

potential difference which causes current to flow

IIIIIIIIIIIIIIIIIIIIIIIIIIIIIIII

Voltmeter

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IIIIIIIIIIIIIIIIIIIIIII

IIIIIIIIIII IIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIe- e-

Pb2+

Pb2+Pb2+

Pb2+

K+

K+

NO 3-

NO 3-

NO 3-

NO 3-

NO 3-

NO

3 -

Mg2+

Mg2+

Mg2+Mg2+

Cath

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e

An

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e

Salt bridge

Pb Mg

Mg Mg2+ + 2e-

Oxidation

Pb2+ + 2e- Pb

Reduction

Lead-acid cells (car battery)Secondary (rechargeable) cells

Charge cycle

PbSO4 + 2H2O PbO2 + 4H+ + SO42- + 2e-

Pb2+ + 2e- Pb Pb2+ Pb4+ + 2e-

Pb Pb2+ + 2e- Pb4+ + 2e- Pb2+

Pb + SO42- PbSO4 + 2e-

PbSO4 + 2e- Pb + SO42-

PbO2 + 4H+ + SO42- + 2e- PbSO4 + 2H2O

oxidationreduction

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