Pre-Laboratory Assignment Use Table 1 as a source of half-equations and reductio

Question

Pre-Laboratory Assignment Use Table 1 as a source of half-equations and reduction potentials for this assignment. 1. Rank the following metals by ease of oxidation, 4. Describe an electrochemical cel that would have from hardest to easiest: Cu; aluminum, Al; Fe; and the following net equation, by answering the tollowing chromium, Cr Fe(s) + Na.(aa) Ni(s) + Fe2+(aq) Write the reduction and oxidation half-equa- (1) tions for the cell. 2. An Al strip is placed in Cuso, solution. (1) Would you expect a spontaneous reaction to occur, based on the net potential? (2) Sketch the electrochemical cell. Identity the Components of the cell as in Figure 1 (2) If your answer to (1) is 'yes,"what would you observe? (3) Write a chemical equation that describes your predicted observations. 3. Describe what you would observe if you placed an Ag strip in an aluminum nitrate solution, Al(NO3)3. (3) Calculate the expected net voltage for this cell. ELEC 450/Electrochemical Half-Cells and Halt-Reactions

Explanation / Answer

1. Oxidation means losing of electrons. So; less electronegative metals are easy to oxidise.

So; among the given metals Al is the hardest to oxidise and Cu is the easiest to oxidise.

So; increasing order of ease of oxidation: Al < Cr < Fe < Cu

2.i) If a metal strip is dipped into CuSO4 solution; a redox reaction will happen. Cu+2 is oxidised to Cu and metal is reduced. So; on basis of net redox potential; it can be predicted wheather the reaction is spontaneous or not. If net potential is positive then the reaction is spontaneous.

ii) If a spontaneous reaction happens; then Cu+2 will be oxidised to Cu and metal will be reduced. So; blue color of copper sulphate will be decolorised.

iii) Suppose the metal is M whose valency is 2. Then the balanced equation is

M + CuSO4 = MSO4 + Cu

3. 3Mg + 2Al ( NO3)3 = 2 Al + Mg3 (NO3)2

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