3. A student constructs a galvanic cell that has a strip of iron metal immersed

Question

3. A student constructs a galvanic cell that has a strip of iron metal immersed in a solution of 0.1M Fe(NO3)2 as one half-cell and a strip of zinc metal immersed in a solution of 0.1M Zn(NO3)2 as the other half-cell. The measured cell potential is less than zero when the positive terminal of the voltmeter is attached to the zinc strip and the negative terminal is attached to the iron strip.

Which half-cell is the anode (Fe or Zn)?

Which half-cell is the cathode?

Do the electrons flow from Zn to Fe or vice versa?

Which metal is more

Explanation / Answer

For a galvanic cell, the standard potential for the reaction must be positive.

Fe2+(aq) + 2e- --> Fe(s) -0.44 V
Zn2+(aq) + 2e- --> Zn(s) -0.76 V

Ecell = cathode - anode
= -0.44 - (-0.76) = 0.32 V

Iron has a higher reduction potential, therefore iron half-cell is the cathode.
And therefore, zinc is the anode.

Fe(s) + Zn(NO3)2 (aq) --> Zn(s) + Fe(NO3)2 (aq)

Remember that reduction, the gain of electrons, occurs at the cathode and oxidation, the loss of electrons, occurs at the anode. Thus, the flow is from the anode to the cathode, where they are consumed in reduction. (From Zn to Fe)

The reducing ability of the metal is given by the activity series. Zn > Fe

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