Video Transcript
Using the standard electrode potentials in the table below, calculate the standard
cell potential for a galvanic cell with the following overall reaction: Sn solid
plus two Cu2+ aqueous reacts to form Sn2+ aqueous plus two Cu+ aqueous.
Whenever we want to find the standard cell potential for a galvanic cell, we need to
examine the two half equations. These two half equations are written as reductions. And sometimes we will see these half reactions written using equilibrium arrows,
although here standard arrows are used. We need to determine which of these two substances is more likely to undergo
reduction.
By default, we know that the substance that is less likely to undergo reduction will
instead be oxidized. The half equation with the higher, or more positive, standard reduction potential
tells the substance which has a greater ability to be reduced. This value is higher and more positive, so we know that copper two plus ions are more
likely to be reduced to copper plus ions than tin two plus ions are to be
reduced. And therefore we can conclude that the copper half reaction is the reduction
reaction. It is written correctly from left to right. Copper is the cathode where reduction occurs.
The half equation with the lower, or more negative, standard reduction potential is
less likely to be reduced, in other words is more likely to undergo oxidation. So, tin metal will be oxidized to tin two plus ions. We need to read this equation right to left. Or we can flip this equation so it reads as an oxidation reaction where tin loses
electrons. Oxidation occurs at the anode. Again, the standard reduction potential of copper two plus is greater than that of
tin two plus. And so, we know that copper is the cathode and tin is the anode.
We are asked to determine the standard cell potential of the cell. Standard cell potential is given the symbol 𝐸 superscript ⦵, where the ⦵ indicates
standard conditions of 25 degrees Celsius, one-atmosphere pressure, and one-molar
electrolyte concentrations. 𝐸 cell is equal to the difference in the standard reduction potentials of the
cathode and anode. We can now substitute our values. Note, there are two minus signs here. Solving, we get an answer of positive 0.291 volts.
Finally, what is the standard cell potential of this galvanic cell? The answer is positive 0.291 volts.
