Introduction
Electrochemistry is a branch of science
that deals with electricity relation to chemical
reactions. Electrochemistry presents the
conversion of chemicals to electricity, whereas
applied commonly in making batteries and fuel
cells that produce electric power.
During an electrochemical reaction,
where electrons were transferred from one
substance to another, the term OIL-RIG is
invented. OIL-RIG stands for ‘Oxidation Is
Losing’ and ‘Reduction Is Gaining,’ where
oxidation loses electrons (oxidized) and
reduction is the one gaining it (reduced).
During 1970’s, galvanic cell was first
introduced by Luigi Galvani, an Italian scientist
with an experiment of a dissected frog’s lower
body. Two wires such as copper wire and zinc
wire were attached to the frog’s exposed nerve
and leg muscle respectively which results on the
muscle contrast that makes the frog’s lower
body to create movement [1]. Galvani concluded
incorrectly that the electricity was coming from
the tissues of the animal. Another Italian
scientist, Alessandro Volta, would later establish
that the source of the electricity was electron
flow between the two metals, and that the frog's
body fluids were just a conducting medium. (For
this reason, galvanic cells are often referred to
as voltaic cells as well). However, Galvani did
uncover the electric nature of nerve impulses.
His frog experiment is considered the beginning
of electrophysiology and the understanding of
how bodies convert information between
chemical and electrical messaging systems [2].
In the laboratory, its scope was to create
a galvanic cell, also known as voltaic cell, in
three different experiments such as 1) standard
potential galvanic cell, 2) galvanic cell with one
unknown electrode and electrolyte solution, and
3) copper concentration solution. A galvanic cell
is composed of two half-cell reactions, with two
electrodes connected in a multimeter where
electrons (𝑒 − ) flow from the anode to the
cathode, and electrolyte solutions that are
connected by a salt bridge soaked in a strong
electrolyte to balance the cell by letting the ions
flow (cations going to the cathode and anions
going to the anode). The two electrodes in a
galvanic cell can either be the same or different,
and electrolyte solutions must be different.
Standard reactions can be observed with a
galvanic cell, and nonstandard reactions can be
calculated.
To easily determine if a galvanic cell
appeared spontaneous or nonspontaneous in
standard form, a standard reduction potential
table can be used, where the ones placed in the
higher part has the higher tendency towards
reduction and the ones placed lower has the
higher tendency towards oxidation. The standard
reduction potential can be applied in
0
0
0
𝐸𝑐𝑒𝑙𝑙
= 𝐸𝑐𝑎𝑡ℎ𝑜𝑑𝑒
− 𝐸𝑎𝑛𝑜𝑑𝑒
Where the higher value will be the cathode and
the lower one will serves as the anode. When the
0
calculated 𝐸𝑐𝑒𝑙𝑙
appeared positive, then the
reaction is spontaneous, and when appeared
negative, then the reaction is nonspontaneous.
Note: there can be manipulation that may
happen when observed in balance redox reaction
between who may be the cathode and the anode.
In nonstandard reaction, a reaction can
be calculated using
0
𝐸𝑐𝑒𝑙𝑙 = 𝐸𝑐𝑒𝑙𝑙
−
𝑅𝑇
𝑙𝑛𝑄
𝑛𝐹
0
Where 𝐸𝑐𝑒𝑙𝑙 is the measured voltage, 𝐸𝑐𝑒𝑙𝑙
is the
standard potential, R is the universal gas
𝐽
constant which is 8.314
, T is the
𝑚𝑜𝑙×𝐾
temperature in Kelvin, n is the number of
electrons transferred in the half-reaction, F as
𝐶
Faraday’s constant which is 96485 𝑚𝑜𝑙, and Q is
the reaction quotient which can either be
[𝑝𝑟𝑜𝑑𝑢𝑐𝑡𝑠]
[𝑜𝑥𝑖𝑑𝑎𝑡𝑖𝑜𝑛]
𝑜𝑟 [𝑟𝑒𝑑𝑢𝑐𝑡𝑖𝑜𝑛] in molarity form.
[𝑟𝑒𝑎𝑐𝑡𝑎𝑛𝑡𝑠]
The experiment aims to present the
electrical energy available from the electron
transfers in a redox reaction in standard,
nonstandard, and concentration cells [3]. Also,
the experiment wants to develop an
understanding about the limitations and possible
errors of the galvanic cell, and calculate cell
potentials in either standard, nonstandard, or
concentrated cells.
Reference:
[1] Wells, D. A. (1872). The science of common
things: A familiar explanation of the first
principles of physical science as cited by
Calmes, J., Ansari, A. F., Ross, E. Galvanic
Cells. Brilliant.org. Retrieved 14:06 November
7, 2021. https://brilliant.org/wiki/galvanic-cells/
[2] Haas, L.F. J Neurol Neurosurg Psychiatry.
1993 Oct; 56(10): 1084 as cited by Calmes, J.,
Ansari, A. F., Ross, E. Galvanic Cells.
Brilliant.org. Retrieved 14:06 November 7,
2021. https://brilliant.org/wiki/galvanic-cells/
[3] SparkNotes Editors (2005). Galvanic Cells.
Retrieved from www.sparknotes.com