chem 102 last lab report

chem 102 last lab report - Abstract Chemical reactions can...

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Abstract Chemical reactions can be used to produce electricity and electricity can be used to cause chemical reactions through oxidation-reduction reactions. The first part of the experiment measures the standard electrode potentials of zinc half cells against the Cu 2 + |Cu half cell with different concentration of both solutions. The more positive the E cell , the more negative ΔG would be, thus, giving us a spontaneous reaction. After comparing the cell potentials, formation constant of [Cu(NH 3 ) 4 ] 2+ and the Ksp of Cu(OH) 2 , we’ve seen that their deviation where great, since for Ksp, the value does not only depend on the concentrations of the reactants but also with their respective ionic strengths. The second part of the experiment measures the formation constant for the tetraamminecopper(II) ion by using colometer. During this experiment, mixed cupric hydroxide and four different concentration of ammonia, the absordance was able to measure by colormeter. By comparing formation constant for the tetraamminecopper(II) ion using two differen methods, the value was closed each other. However, there are many different factors affecting the value of the cell potential, the emf reading, and measruing the concentration namely: concentration, temperature and reaction quotient. Other than human error, these factors affect the calculated values for formation constant. There is a significant percent difference from the theoretical and the experimental value on K f which is -116.145% for the first method and -900.703746264%for the second method. The sources of error are incorrect solution preparation and contaminated materials. As the observes the percentage error on both method the Galvanic cell has less percentage error so that we can say that there is less factors of error on first part of the experiment. Introduction
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Chemical reactions can be used to produce electricity and electricity can be used to cause chemical reactions. The practical applications of electrochemistry are countless, ranging from batteries and fuel cells as electric power sources, to the manufacture of key chemicals, to the refining of metals, and to the methods of controlling corrosion. Electrochemistry always involves an oxidation-reduction process, wherein electrons are transferred from one substance to the other. This reaction is thermodynamically spontaneous and thus releases energy in the form of heat into their surroundings, and when in a controlled system, it produces electricity. Devices which carry out this process are called electrochemical cells. The objective of this experiment is to measure the standard electrode potentials of half cells against the Cu 2 + |Cu half cell and to use the standard electrode potentials to predict whether or not a reaction will occur. The standard electrode potential, Eºcell, is the electric potential that develops on an electrode when the oxidized and reduced forms of some substance are in their standard states. When used in electrochemical studies, a strip of metal is called the electrode.
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This note was uploaded on 03/08/2011 for the course CHEM 102 taught by Professor Duzut during the Spring '11 term at Los Angeles City College.

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chem 102 last lab report - Abstract Chemical reactions can...

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