Experiment 4: Constructing an iron/ copper cell
· An iron/ copper cell was set up by connecting the same Fe/ Fe2+ and Cu/Cu2+ half-cells that was used in the previous two experiments. · Again, a fresh salt bridge was used. · The E0cell was recorded. Experiment 5: Effect of concentration on E0cell · Le Chatelier’s principle was used to predict the changes that occur if the ion concentration in each equilibrium system is reduced. · What will be the effect of decreasing the concentration of the copper ions on the tendency for the copper electrode to accept electrons from the zinc? · What will be the effect on E0cell of decreasing the concentration of copper ions? - A Zn/Cu cell was set up similar to that of experiment 2 but featuring 0.001 M Cu2+ instead of 1 M Cu2+. · E0cell was also measured with the following concentrations of Cu2+ : - 0.01 M - 0.1 M - 1 M (this is a re-measurement) · A fresh salt bridge was used each time (at the low concentrations, it is very important to pay careful attention to possible contamination in the copper half=cells as small quantities of impurities would give rise to large errors). · A graph of E0cell versus log [Cu2+] was plotted featuring four data points.
IV. Results Experiment 1: Reaction between Zn and Cu2+ Zn(s) +Cu2+ (aq) → Cu0 (s) ↓ + Zn2+ (aq) Observations: Solid, Zn, replaced Cu (II). Copper became precipitate, and the test tube became darker. Zn is oxidized, while the copper is reduced. This is exothermic reaction.
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