1. What is happening at the cathode of an operating electrochemical cell and wha

Question

1. What is happening at the cathode of an operating electrochemical cell and what sign is traditionally given to this electrode? What color wire is traditionally used to connect to the cathode?

2. A positive voltage will indicate that the voltmeter is connected correctly to the electrochemical cell (battery). How will you know what 1/2 cell is acting as an oxidation?

3. The reduction potential for the copper(II) ion to copper metal reaction is +.34 volts. If a cell is made with copper(II)/Cu and Fe(II)/Fe 1/2 cells and a voltage of .8 volts is recorded with the copper 1/2 cell acting as the cathode, what is the reduction potential of the Fe(II)/Fe half reaction?

4. Two identical Cu(II)/Cu half cells are properly hooked up to a volt meter. What voltage should be seen on the meter?

5. Now ammonia is added to one of the half cells and a voltage is measured when the ammonia containing cell is the anode.   What is happening here? Would the Nerst equation allow the calculation of the stability of the copper(II) - ammonia complex? Explain.

Explanation / Answer

1.

a) cathode: reduction occurs here, electrons flow to cathode

b) The cathode is marked as + traditionally

c) The red wire goest to the positive (cathode)

2.

a) Since it is positive Voltage, you may be sure the half cell acting as oxidation will be the anode, the negative one or the black wire conected to the anode

3.

Cu+2 ---> Cu E = 0.34V

Fe+2 ---> Fe E =

Ecell = 0.80 V

Copper is acting as cathode, therefore it is being reduced

Iron will be oxidiezd

Fe ---> Fe+2 +2 e- E = x V

Ecell = Ered - Eox = 0.34 - (xV) = 0.80

V = -.80+0.34 =

a) E = -0.46 V

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