Determination of Avogadro\'s Number (Electrolytic Cell) (Anode) Before Electroly

Question

Determination of Avogadro's Number (Electrolytic Cell) (Anode) Before Electrolysis After Electrolysis 6798 Weight electrode Weight electrode 2 1.7806 g LH86 g Time Amps Time Amps 0.00 Start 11.00 min 1.00 min 6 2.00 min 3.00 min 5 2 12.00 min 13 4.00 mirn 15.00 r 5.00 min 05O 0.5I min 1700 min.S (18.00 min)O.SO (19.00 min) -0.3 (20.00min) -0,54 6.00 7.00 min 8.00 min 9.00 mino.R 10.00 min S3 Toal time0 In (min and) (21.00 min) (min and sec) Observations: (Anything observed, including spills, amp fluctuations, touching electrodes, spills scratches, bubbles, etc.) Electrochemistry LExperimest

Explanation / Answer

I)

If you dip a rod of zinc into a copper solution, this is exactly what happens—the zinc dissolves and small beads of copper are reduced on its surface, no second electrode required. Trying to make a zinc-copper cell with copper ion in the solution just makes the cell work worse as a good part of the zinc is lost through direct reduction of copper ions at the surface. The way to prevent this is to separate the two half-reactions with a salt bridge.

The reason the electrons leave in the first place (why the oxidation reaction above occurs) is that it is more energetically favourable for the zinc to be oxidized in the solution than to remain in its metallic state. Another way to think about is that zinc is more easily oxidized than copper so it must have electrons that are more easily lost (have a greater electrochemical potential) and these electrons will flow towards a lower electrochemical potential. Therefore, when you connect the two electrodes together, electrons flow from zinc to copper until an equilibrium is reached. Copper's electrons are not normally high enough energy to reduce the hydronium ion, but because of the electrons coming from the zinc, its electrochemical potential is raised enough for the reaction to occur.

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