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Electrochemistry Pg 132
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Electrochemical Cells
Made of two half-cells Based upon two half-reactions Electrons travel between the two half-cells
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Types of Cells Also called voltaic cells
Convert chemical energy into electrical energy Spontaneous Convert electrical energy into chemical energy Non-spontaneous Galvanic Cells Electrolytic Cells
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Making a Galvanic Cell Mg (s) + CuSO4 (aq) MgSO4 (aq) + Cu (s)
Write the reaction for solid magnesium placed in a copper (II) sulfate solution and assign oxidation numbers. Mg (s) + CuSO4 (aq) MgSO4 (aq) + Cu (s)
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Making a Galvanic Cell Mg (s) Mg2+ (aq) + 2e-
Balance the reaction using the half-reaction method +2 +6 -2 +2 +6 -2 Mg (s) + CuSO4 (aq) MgSO4 (aq) + Cu (s) Mg (s) Mg2+ (aq) + 2e- Cu2+ (aq) + 2e- Cu (s)
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Making a Galvanic Cell 1(Mg (s) Mg2+ (aq) + 2e-)
Balance the reaction using the half-reaction method +2 +6 -2 +2 +6 -2 Mg (s) + CuSO4 (aq) MgSO4 (aq) + Cu (s) 1(Mg (s) Mg2+ (aq) + 2e-) 1(Cu2+ (aq) + 2e- Cu (s)) Mg (s)+CuSO4 (aq)+2e- MgSO4 (aq)+Cu (s)+2e-
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Making a Galvanic Cell
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Making a Galvanic Cell Anode (Oxidation) Cathode (reduction)
Salt Bridge Flow of electrons
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Measuring the Output of a Galvanic Cell
Potential (either half-cell or cell) Pull on the electrons Voltmeter Analog Digital Positive potential…spontaneous Negative potential…nonspontaneous
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Measuring the Output of a Galvanic Cell
Standard Reduction Potentials Chart Only reduction reactions Must look up the reverse of the oxidation and flip the sign of the potential Add standard half-cell potentials to get standard cell potential
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Measuring the Output of a Galvanic Cell
1(Mg (s) Mg2+ (aq) + 2e-) E˚ox= V 1(Cu2+ (aq) + 2e- Cu (s)) E˚red= V Mg (s)+CuSO4 (aq)+2e- MgSO4 (aq)+Cu (s)+2e- E˚cell = V
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Writing a Line Notation
Oxidation||Reduction X(s)|X+(aq)||Y+(aq)|Y(s) Mg(s)|Mg2+(aq)||Cu2+(aq)|Cu(s) 1(Mg (s) Mg2+ (aq) + 2e-) 1(Cu2+ (aq) + 2e- Cu (s)) Mg (s)+CuSO4 (aq)+2e- MgSO4 (aq)+Cu (s)+2e-
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