Mustafa_COKSUN_Lab_Report_8

Mustafa_COKSUN_Lab_Report_8 - OBJECTIVE In this laboratory...

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OBJECTIVE In this laboratory session, we aim to obtain liquid state thermochemical data on the Sn-Bi alloy system. APPARATUS *furnace *multimeters *electrode *thermocouple *electrolytes (pure Sn and fused salt) SAMPLE *Tin-Bismuth alloy with X Sn = 0,2 THEORY Thermochemical Information An electrochemical cell is such a device that electricity is generated inside it. Electricity is produced via a set of spontaneous oxidation and reduction reaction. Galvanic Cell A simple voltaic cell in which Cu and Zn electrodes are used. Cu is immersed into copper sulphate solution and Zn is immersed into zinc sulphate solution. Zinc is oxidized at anode; Zn (s) → Zn 2+ (aq) + 2e - Copper is reduced at cathode; Cu 2+ (aq) + 2e - → Cu (s) The emf generated by the cell is, denoted as E,
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The free energy change due to 1 mole of cell reaction; Δ G = –nFE Concentration Cells A potantial difference can be produced when the compartments of the cell are of the same material with a different concentration. In which; [ ] [ ] M1 M2 ln xF RT - × E Cells with Fused Salt Electrolytes Such cell that operate at high temperatures at which their salt electrolytes are molten. Helpful in obtaining data about the thermodynamic properties of compaunds and solutions. a) Formation Cell General purpose for using this type of cell is to get information about thermochemical properties such as enthalpy, entrpy or Gibb free energy.
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Overal Reaction is; Pb (l) + ½ O2 (g) = PbO (l) The emf; where Q = a PbO /a Pb .a Po2 ½ Since PbO and Pb are pure; a PbO =1, a Pb =1. As P o2 =1; E = E ο G = -zEF=-zE ο F Thermodynamical Equations X A M A + X A M B = {X A M A +X B M B } When two metals forma a solution; the Gibbs free energy change is; G=G-G o Where, G o = X A G o + X A G o G = X A G A M + X B G B M G A M and G B M are related to thermodynamic activites; G A M = RTrlna A and G B M = RTlna B Also excess Gibbs free energy is; G i xs = R T ln γ i Gibbs-Duhem relates activity of one to that of other at a given composition; X A dlna A + X B dlna B = 0 The data related tp enthalpy terms in the solution can be obtained from the expression; G = H - T S
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PROCEDURE We have heated the Sn-Bi alloy to 400 o C and then we have taken mV data from voltmeter
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This note was uploaded on 12/27/2011 for the course MATH 286 taught by Professor Adad during the Spring '11 term at Middle East Technical University.

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Mustafa_COKSUN_Lab_Report_8 - OBJECTIVE In this laboratory...

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