Video Transcript
The cell diagram of two connected
half-cells consisting of aluminum and copper is as follows. What does the double vertical line
in the center of the cell notation represent? (A) The two metal electrodes, (B)
the high-resistance voltmeter, (C) the salt bridge, (D) a switch, (E) standard
conditions of 298 kelvin and one atmosphere.
In this question, we are given a
cell diagram which is a universal method used by chemists to represent information
about galvanic cells. It is also referred to as cell
notation. In some ways, the cell notation
represents the actual apparatus used for a galvanic cell. A galvanic cell is a type of
electrochemical cell, where electrons are generated spontaneously through a redox
reaction and these electrons pass through an external circuit.
Let’s have a look at the setup of a
galvanic cell. A galvanic cell is composed of two
half-cells. Each half-cell has an electrode
immersed in a solution of its ions, in this case aluminum and copper electrodes in
Al3+ and Cu2+ electrolytes, respectively. The two half-cells are connected by
a salt bridge. We can measure the potential
between the two electrodes using a high-resistance voltmeter. The cell notation mirrors this
experimental setup.
The information on the left side of
the double vertical line is information about the aluminum half-cell. We call the aluminum electrode the
anode, and the anode undergoes oxidation in a galvanic cell. Information about the electrode is
written first. Then, details of the anode
half-cell electrolyte solution are given, including the ions present and their
concentration. Next, a double vertical line is
drawn. This represents the salt bridge,
which completes the circuit by connecting the two solutions.
On the right-hand side information
about the cathode half-cell is written. This is the half-cell where
reduction occurs, and in this case copper ions are reduced and plated onto the
copper electrode, which we call the cathode. First, details for the electrolyte
solution are given. And finally, we are told what the
cathode is made from, in this case copper.
We were asked what the double
vertical line in the cell notation represents. The answer is (C), the salt
bridge.
