Video Transcript
A galvanic cell is represented by
the cell notation Zn solid, Zn2+ aqueous, Sn2+ aqueous, Sn solid. What is the ionic half equation
that occurs at the anode of the cell?
In this question, we want to deduce
the ionic half equation for the anodic side of a galvanic cell given its cell
notation. Cell notation is a standard format
used by chemists to explain the construction of an electrochemical cell. Since this is a standard format,
the anode information is always written on the left-hand side of the double vertical
line of the cell notation. And the cathode details are written
on the right-hand side. We are told that this is a galvanic
cell. In a galvanic cell, a spontaneous
redox reaction generates electrons, and so we say that chemical energy is converted
to electrical energy in this cell.
Let’s investigate this cell
notation in more depth. The cell notation tells us that
there is a solid zinc electrode placed in a solution of zinc two plus ions. This forms one half-cell. And on the other side, we have a
solution of tin two plus ions into which is placed an electrode made of tin
metal. This is the second half-cell. A salt bridge, denoted by two
vertical lines, creates an electrical connection between these two half-cells. And the electrodes are connected by
wires and possibly a device that will be powered by this electrochemical cell, for
example, a light bulb. These two single vertical lines
indicate a phase boundary exists between the solid electrodes and their aqueous
solutions of ions.
In a galvanic cell, oxidation
occurs at the anode. We read the cell notation left to
right. And so we can see that at the anode
zinc metal is converted, or oxidized, to zinc two plus ions. The half reaction for this
oxidation process is Zn solid reacts to form Zn2+ aqueous plus two electrons. This anode half equation is what we
were asked to find in the question.
To complete our knowledge, let’s
quickly look at the cathodic half reaction. Again, we need to read the cell
notation from left to right. We can see that at the cathode tin
two plus ions are converted, or reduced, to tin metal. Reduction occurs at the
cathode. So the half equation for the
cathode would be Sn2+ aqueous plus two electrons reacts to form Sn solid.
Finally, what is the ionic half
equation that occurs at the anode of this cell? The answer is Zn solid reacts to
form Zn2+ aqueous plus two electrons.
