8303121-041-Ques-Cells-n-SEP

8303121-041-Ques-Cells-n-SEP - Chem Factsheet September...

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Answering Questions on Electrochemical Cells C hem F actsheet September 2002 Number 41 1 This Factsheet assumes you know and understand the basics of cells and standard electrode potentials (covered in Factsheet 37). It will concentrate on applying that knowledge to examination questions on cells. There are three main types of question on electrochemical cells. Actual examination questions will usually contain more than one of these. (1) Recall of basic facts You can be asked to give the following: (a) a drawing/description of the standard hydrogen electrode. (b) the definition for a standard electrode potential. (c) a drawing of the apparatus used to measure standard electrode potentials (d) an explanation of why a high resistance voltmeter is used. (e) an explanation of why potassium nitrate is used for the salt bridge. (f) a description and explanation of the trend in oxidising and reducing powers related to the E ê table of values. All of these are covered in Factsheet 37. . Worked Example What is the cell reaction when the following half cells are combined? V 3+ +e ¾ V 2+ E ê = -0.26V Ni 2+ +2 e ¾ Ni E ê = -0.25V Method Answer Identify the cathode V 2+ | V 3+ is the more negative electrode so it is the cathode Reverse the equation V 2+ ¾ V 3+ + e for the cathode. Write down the Ni 2+ +2e ¾ Ni equation for the anode "Balance" the electrons There are two electrons in the nickel equation in the two equations but only one in the vanadium equation.
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This note was uploaded on 03/08/2011 for the course CHEM 101 taught by Professor Hard during the Spring '11 term at UT Arlington.

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8303121-041-Ques-Cells-n-SEP - Chem Factsheet September...

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