chap17notes - Chapter 17 Electrochemistry 17.1 Galvanic...

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1 Chapter 17 – Electrochemistry 17.1 Galvanic Cells A. Oxidation-Reduction Reactions (Redox Rxns) 1. Oxidation = loss of electrons a. the substance oxidized is the reducing agent 2. Reduction = gain of electrons a. the subtance reduced is the oxidizing agent B. Redox energy 1. Heat is produced 2. Electricity can be produced if the reactants are separated a. Reactants can be separated by a salt bridge b. Reactants can be separated by a porous partition c. Electrons travel through a wire C. Galvanic Cell 1. A device in which chemical energy is changed to electrical energy a. Oxidation occurs at the anode b. Reduction occurs at the cathode D. Cell Potential ( cell ) 1. The driving force (electromotive force, emf) on the electrons 2. Potential is measured in volts 17.2 Standard Reduction Potentials A. Measuring Potential 1. Electrode potential is measured in reference to a hydrogen electrode which is arbitrarily assigned a potential of zero volts
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2 B. Calculating Electrode Potential 1. One of the reduction half reactions must be reversed, changing the sign on the potential for the reversed reaction 2. Potentials are not multiplied by the coefficients in the balanced equation 3. Galvanic cell potentials must be a positive number C. Line Notation 1. Anode components listed on the left 2. Cathode components listed on the right 3. Double line represents salt bridge or porous disk Mg(s) Mg 2+ (aq)  Al 3+ (aq) Al(s) D. Complete Description of a Galvanic Cell 1. The cell potential (always positive for a galvanic cell) 2. The direction of electron flow (the direction that yields a positive potential) 3. Designation of the anode and cathode 4. The nature of each electrode and the ions present in each compartment. A chemically inert conductor (such as Pt) is required if none of the substances participating in the reaction is a conducting solid 17.3 Cell Potential, Electrical Work, and Free Energy A. Driving Force 1. emf = potential difference = work (joules)
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chap17notes - Chapter 17 Electrochemistry 17.1 Galvanic...

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