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课件网) Chapter 19 Electrochemistry Electrochemistry 19 19.2 Galvanic Cells 19.3 Standard Reduction Potentials 19.4 Spontaneity of Redox Reactions Under Standard-State Conditions 19.5 Spontaneity of Redox Reactions Under Conditions Other Than Standard State The Nernst Equation Concentration Cells 19.6 Batteries Dry Cells and Alkaline Batteries Lead Storage Batteries Lithium-ion Batteries Fuel Cells 19.7 Electrolysis Electrolysis of Molten Sodium Chloride Electrolysis of Water Electrolysis of an Aqueous Sodium Chloride Solution Quantitative Applications of Electrolysis 19.8 Corrosion Static Electricity Happens Everywhere Lightning Triboelectricity 摩擦电 Atoms bind electrons slightly differently. If you rub any two neutral different materials together, some electrons may transfer from one to the other resulting in oppositely charged objects. The amount of charge is generally small - a nanocoulomb or so. Tribo means rubbing Triboelectricity Triboelectric Series Zn(s) + Cu2+(aq) → Zn2+(aq) + Cu(s) Galvanic Cells 19.2 When zinc metal is placed in a copper(II) solution, Zn is oxidized and Cu2+ ions are reduced. Galvanic Cells The experimental apparatus for generating electricity through the use of a spontaneous reaction is called a galvanic cell. Galvanic Cells Electric current flows from anode to cathode because there is a difference in electrical potential energy between the electrodes. The electrical potential is measured by a voltmeter and is called the cell potential (Ecell ). Cell notation: Zn(s) │ Zn2+ (1 M) ││ Cu2+ (1 M) │ Cu(s) anode cathode Notation for a Voltaic Cell components of anode compartment (oxidation half-cell) components of cathode compartment (reduction half-cell) phase of lower oxidation state phase of higher oxidation state phase of higher oxidation state phase of lower oxidation state phase boundary between half-cells Examples: Zn(s) | Zn2+(aq) || Cu2+(aq) | Cu (s) Zn(s) Zn2+(aq) + 2e- Cu2+(aq) + 2e- Cu(s) graphite | I-(aq) | I2(s) || H+(aq), MnO4-(aq), Mn2+(aq) | graphite inert electrode Standard Reduction Potentials When the concentrations of Zn2+ and Cu2+ are 1 molar at 25°C, the cell voltage is 1.10 V. 19.3 Zn(s) + Cu2+(aq) → Zn2+(aq) + Cu(s) Voltages of Some Voltaic Cells Voltaic Cell Voltage (V) Common alkaline battery Lead-acid car battery (6 cells = 12V) Calculator battery (mercury) Electric eel (~5000 cells in 6-ft eel = 750V) Nerve of giant squid (across cell membrane) 2.0 1.5 1.3 0.15 0.070 Metal Surface Solution Electrode Potential 电极电位 Potential Difference here and forms a Bilayer 双电层 Electrode potential depends on the properties of the metal, temperature, solution characteristics and concentration. Agar-agar 琼脂 + KNO3 A voltaic cell based on the zinc-copper reaction. Oxidation half-reaction Zn(s) Zn2+(aq) + 2e- Reduction half-reaction Cu2+(aq) + 2e- Cu(s) Overall (cell) reaction Zn(s) + Cu2+(aq) Zn2+(aq) + Cu(s) A voltaic cell using inactive ... ...
