CHEM 122 - ELECTROCHEMISTRY II

# CHEM 122 - ELECTROCHEMISTRY II - Notes from A previous...

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Notes from A previous class: the SI unit of charge is the COULOMB, C. One coulomb of charge on each of two point object that are 1.00 M apart will result in each object exerting a force of 9.0 x 10(9) Newtons on each other, an enormous force. This is equal to the weight of about a million tons. There are two types of charge, positive and negative. The charge on one electron has been determined to be 1.602 x 10(-19) coulombs. This is the smallest charge found in nature. It is fundamental and symbolized by e^-, and called the elementary charge. e = 1.602 x 10^-19 (it has been determined to be 1.602177 - 7 sig figs). What is the charge on a mole of electrons? 1.602177 x 10^-19 x 6.022x10^23 = 96,485 C/mol e- = F F is Faraday's constant. F = q/mol or q = n x F In the reaction Iron(III) + Vanadium(II) yields Iron(II) + Vanadium(III), one ielectron is transferred to Iron(III) from Vanadium(II). If we know how many moles of electrons are transferred from vanadium(II) to Iron(III), we can know how many moles of product have been formed. Example: Relating Coulombs t quantity of reaction: If 5.585g of Fe(III) ions are reduced in the reaction above, how many coulombs of charge were transferred? (q = 9,649 C). Electric current is proportional to the rate of a redox reaction. Electric current (I) is the quantity of charge flowing each second past a point in an electric current. The unit of current is the ampere (A), which represents a flow of 1 C per second. 1A = 1C/s

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UPDATED NOTES FROM LECTURE Galvanic (Voltaic) Cells To generate electrical energy to do work, one of the reagents must be oxidized, and another must be reduced. (Which is an electron transfer process - the movement of electrons from one reagent to another is what is harnessed for the work). Electrons are transferred between the two, however, the two cannot be in contact or electrons would flow directly between them without going through the external circuit. When we make a galvanic cell, we physically separate those two half reactions. Therefore the oxidizing and reducing agents are physically separated, and electrons flow through a wire to get from one reactant to the other. (See fig. 19.1 in the book). There are two beakers - in each is a half reaction. To metal electrodes are immersed in the solutions. The electrodes are connected by an external circuit, connected by a voltmeter, reading volts. The beaker on the left contains a Zinc Sulfate solution with a Zinc electrode. The other beaker has a copper tube and a Copper Sulfate solution. At the phase boundary between the solid electrodes and the liquid phase of the solution, there is a connection that is being established. The zinc atom has a good tendency to lose electrons and become an ion.
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## This note was uploaded on 02/02/2011 for the course CHEM 122 taught by Professor Bellew during the Fall '07 term at New Mexico.

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CHEM 122 - ELECTROCHEMISTRY II - Notes from A previous...

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