Galvanic Cells & Calculations of Cell Potential Discussion

Electrochemistry: Galvanic Cells and the Calculations of Cell Potential

INTRODUCTION:

Electrochemistry is the study of chemical reactions which involve the transfer of electrons. It also includes the study of relationships between chemical reactions and electricity, in able to perform a beneficial electrical work, galvanic cells bind the electrical energy available from the electron transfer in a redox reaction. This is by splitting the oxidation and reduction reactions, the transfer of electron takes place through an external route instead of straight between reactants. Two half cells are linked by a wire, so that the electrons are able to flow through that wire. In order for the circuit to be completed, a salt bridge is needed.

Materials and Method:

  • 100mL of each metal solution
  • Metal electrodes ( Mg, Fe)
  • Voltmeter with alligator clips
  • Filter paper and 1.0M KNO3 for the salt bridge

The salt bridge was prepared by placing a strip of the filter paper in 1.0M KNO3 solution to be absorbed. The prepared salt bridge was removed from the solution it was soaked in and drapped, connecting the beakers without them physically touching. Both ends of the strips was then immersed in a beaker filled with the chosen solution creating the salt bridge. Each corresponding metal electrode was connected to a voltmeter via the alligator clips connecting the (-) to the anode and the (+) to the cathode. Each electrode was placed into its matching beaker without it touching the salt bridge avoiding a short circuit of the cell if they were to touch. The voltmeter was then switched on, pitting it at 20 volts. The potential difference of the cell was shown and recorded after a stable reading on the voltmeter. The cell was left to settle for around five minutes to see if there were any qualitative observations and any visual changes were recorded. Below is an example of a galvanic cell and it usually includes:

  • The half cell that was the cathode and the half-cell that is the anode
  • The metal that was the anode and the metal that was the cathode
  • The solutions in each beaker
  • The direction that the electrons flow through the wire
  • The directions ions would migrate in the salt bride when the cell is operating
  • The relevant balanced half-cell equations underneath each cell

Hypothesis:

For a reaction to be spontaneous, the standard electrode potential must be greater than zero, which means it must be positively charged. Hence cell with positive standard electrode potential can conduct electricity.

Results:

Reduction Potentials of Redox Couple

Galvanic cell combination

Ecell measured(V)

Anode

Equation for Anode reaction

Cathode

Equation for Cathode Reaction

Fe-Mg

1.92

Mg

Mg— Mg2+ +2e

Fe

Fe2+ + 2e —- Fe(s)

A redox reaction is spontaneous if the standard electrode potential for the redox reaction is positive

E0redox reaction = Eoreduction reaction + Eo oxidation reaction

From the above we can conclude that the cell is spontaneous as the galvanic cell potential are all greater than zero , which means the cells are able to conduct electricity.

Magnesium-Iron galvanic cells is based on spontaneous reaction between solid magnesium and aqueous iron (iii) ions. In this cell, a solid mg anode is immersed in aqueous solution of MgCl2 that is connected via salt bridge to an aqueous solution containing a mixture of FeCl3 and FeCl2 immersed in a platinum cathode. Note that in this case, cathode half-cell is different from the other, because here cathode is comprised of a substance (Pt) that is neither a reactant nor a product of the cell reaction, this is required when none of the member of half-cell redox couple can junction as electrode, which must be electrically conductive and in a phase separate from the half-cell solution. Now, in this case both members of redox couple are solute species, so Pt is used as inert electrode that can simply provide or accept electrons to redox species in solution.

Net cell reaction: Mg (s) + 2Fe3+(aq) — Mg2+(aq) + 2Fe2+(aq)

Oxidation half reaction: Mg(s) — Mg2+(aq) + 2e

Reduction half reaction: 2Fe3+(aq) + 2e — 2Fe2+(aq)

Overall reaction:

Mg(s) + 2Fe3+(aq) — Mg2+(aq) + 2Fe2+(aq)

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Figure 1

In figure 1 above, shows the reaction between Magnesium and Iron in the galvanic cell. The anode in this case is Magnesium and it is being oxidized, that means that magnesium ions were being produced due to loss of electrons. The cathode was Iron and it was being reduced which means there was gaining of electrons.

Electrochemistry is the study of chemical reacons which involve the transfer of electrons. It

also includes the study of relaonships between chemical reacons and electricity. In able

to perform a benecial electrical work, galvanic cells bind the electrical energy available

from the electron transfer in a redox reacon(SparkNotes Editors, n.d.). This is by spli$ng

the oxidaon and reducon reacons, the transfer of electrons takes place through an

external route instead of straight between reactants. Two half cells are linked by a wire, so

that the electrons are able to %ow through that wire. In order for the circuit to be

completed, a salt bridge is needed. Galvanic cells can also be referred to as voltaic cells

which general uses spontaneous redox reacons to generate electrici

CONCLUSION

The galvanic cell reaction was spontaneous and Is able to be a conductor if electricity. The half-cell was set up in beakers being connected by the salt bridge. The anode was negative and the cathode is the more positive electrode. The reaction that occurs at the anode is oxidation and at the cathode reduction occurs. Electron being supplied by the substances getting oxidized where they move from the anode to the cathode in the circuit. The oxidation and reduction half-reactions are joined by a wire, so that the electrons flow through that wire. A current is sent through the circuit which explains why they could be used for a number of electrical purposes. When two half-cells are combined by a salt bridge that allows ions to pass between two sides maintain electronegativity. These cells are essential because they are the foundation for the batteries that fuel modern society. Two or more cells that are connected together is what forms a battery. That is the principles of cells in order to make electrical batteries.

With regards to the earlier hypothesis, displacement reactions involve a transfer of electrons, galvanic cells use cell notation and use of tables of standard reduction potential. Earlier predictions were made if spontaneous reactions would occur with a given species and in this case all pairs of the half-cell simultaneously reacted, potential difference were observable but there was no significant current that can flow as well as no significant chemical change. The flow of electrons creates the electrical current.

Hence the above validates the hypothesis, therefore we can conclude this experiment was successful

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