HShin_Hoon_Shin_-_Lab_Report_4

HShin_Hoon_Shin_-_Lab_Report_4 - iAuthor: Hoon Shin TA:...

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iAuthor: Hoon Shin TA: Eileen Chen Section: A05 Class: Chem100A, UCSD(University of California San Diego) Date: 5/05/08 Electrochemistry Abstract For first part of the lab, one was ask to set up the Daniell cell of the zinc solution and copper solution. Then the solutions of different concentration and different combinations were measured by pH meter. For different combination, the cell voltage of 0.10M ZnSO 4 and 0.10M CuSO 4 , 0.10M ZnSO 4 and 0.0010M CuSO 4 , and 0.0010M ZnSO 4 and 0.10M CuSO 4 were 1089.3mV, 1061.3mV, and 1059.3mV respectively. Cell voltage for combination of different concentrations for 0.10M CuSO 4 and 0.0010M CuSO 4 , 0.10M CuSO 4 and 0.00010M CuSO 4 , 0.10M CuSO 4 and 0.000010M CuSO 4 , and 0.10M CuSO 4 and 0.0000010M were observed as 45.8mV, 59.3mV, 72.8mV, and 98.1mV, respectively. For the second part of experiment where one must observed the amount of ascorbic acid in a vitamin tablet by performing redox titrations, the standardized concentration of thiosulfate solution was 0.0979M ± 0.0027 and the amount of ascorbic acid was 396.7mg ± 0.3mg which is little off from the expected value of 500mg. Introduction Purpose of this lab is for one to understand about electrochemistry. Part of the electrochemistry, it includes redox reaction which is oxidation and reduction. When the species lost the electrons, it is called oxidation or the reducing agent. When the species gained the electrons, it is called reduction or oxidizing agent. Also, the reactions must happened at the same time, in other words, it is impossible to have reduction reaction without an oxidation reaction and vice versa. This redox reaction can set up in electrochemical cells. In the cell, oxidation reaction and reduction reaction can be separated physically. In the reaction, place where oxidation reaction
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occurs is called anode and where reduction reaction occurs is called cathode. For this reaction to interact each other, two species must have salt bridge which is a bridge between two species that act as bridge for electrons to move around. With this electrons moving around, one can measure the cell voltage by using pH meter. Using this value, one can calculate the cell voltage by this equation called Nernst Equation: Q RT E E log nF 303 . 2 - = “n” equals to the number of electrons that has been transferred, T is a temperature, and Q is a concentration of product divided by the reactants where R and F are constant. In the first part of this experiment, one will construct a Danielle cell using zinc and copper with zinc sulfate solution and copper sulfate solution where zinc being the anode and copper being cathode. As a result, one will learn the relationship between the concentration and potential of this redox reaction. In the second part of this experiment, one must calculate the amount of ascorbic acid in a
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HShin_Hoon_Shin_-_Lab_Report_4 - iAuthor: Hoon Shin TA:...

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