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Chemistry IA GRADE 7
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IA for IB curriculum, grade 7 awarded, in depth analysis, marked against 2021 IB rubric, structured
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Investigating the mass of electrodes as determined both by theoreticalpredictions and Faraday’s laws of electrolysis
Candidate code: jbd581
, Electrolysis of copper sheet metal in a solution of copper (ii) sulphate over the time period
of 20m : How does the mass of copper electrodes vary over time, investigated both by
measuring the mass of copper electrodes every 2 minutes and through theoretical
predictions using Faraday’s laws of electrolysis
1 Introduction
Growing up, I have purchased plenty of jewellery, and one recurring issue I have faced is the
rusting and tarnishing of these pieces. This occurs due to the metal reacting with oxygen in
the presence of water in air. This is in fact a major industrial issue globally and is an
economically important process for manufacturers. One way to tackle this problem, is by
coating iron and steel in a layer of metal that is not prone to corrosion and more rust-
resistant. This is the process of electroplating and can be defined as “the process of plating
one metal onto another by electrolysis, most commonly for decorative purposes or to
prevent corrosion of a metal”.1
When we studied electroplating in the redox processes topic, I was fascinated by the
concept and wondered whether there was a formula to predict the mass deposited and lost
on electrodes. Upon further research, I discovered that Faraday’s laws for electrolysis can
be used to predict mass of electrodes. I later found that this is covered in the HL Chemistry
syllabus, and although I am an SL student, I was curious to learn more about his law and
how it can be manipulated to predict the mass of electrodes. This led me to the research
question How does the mass of copper electrodes vary over time, investigated both by
measuring the mass of copper electrodes every 2 minutes and through theoretical
predictions using Faraday’s laws of electrolysis?
2 Aim
In this IA, I will investigate the electroplating process of copper. My aim is to determine the
relationship of the mass of copper plated on electrodes over time. I will do this by carrying
out an electrolysis of copper electrodes in a solution of copper (ii) sulphate and measuring
the mass of the electrodes every 2 minutes for 20 minutes. Faraday’s law states that the
mass of metal electroplated is directly proportional to the of current passing through circuit.
2
So I will be comparing my experimental results with the theoretical results predicted using
Faraday’s laws of electrolysis.
1
Libretexts. “Electroplating.” Chemistry LibreTexts. Libretexts, August 15, 2020.
https://chem.libretexts.org/Bookshelves/Analytical_Chemistry/Supplemental_Modules_(Analytical_Chemistry
)/Electrochemistry/Electrolytic_Cells/Electroplating.
2
Talbot et al. “Redox Processes .” Essay. In Chemistry for the IB Diploma. London: Hodder Education, 2015.
1
, 3 Background Information
Electroplating
The process of electroplating is demonstrated in Fig. 1. The process involves passing an
electric current through a solution, called an electrolyte, which will be composed of the
metal to be plated. This is done by having two terminals that are placed inside the
electrolyte, called electrodes. The electrode connected to the positive side of the power
supply is the anode, while the one connected to the negative side is called the cathode,
which is the side the object to be plated is placed. The metal at the anode will lose electrons
to the electrolyte and the metal at the cathode will gain electrons and metal cations in the
solution will combine with these electrons to form a layer of solid metal on cathode. 3 The
concentration of the solution thus remains constant, as the aqueous cations that form the
metal coating on the cathode are replenished by the metal that is released at the anode. 4
A commonly used metal for rust-resistant protection is copper, as it can fight corrosion due
to the protective layer it produces when in contact with oxygen. Copper is below water in
the standard electrode potential table and thus it is a stronger oxidising agent. This means it
will be reduced at the cathode and so a layer of copper will be deposited on this side. The
anode’s role is to keep the concentration of the solution constant.
5
Fig. 1 Electroplating process
The half reactions at the electrodes:
Electrode half reactions Standard Electrode Potential
Cathode Cu2+(aq) + 2e– ---> Cu(s)
Anode Cu(s) – 2e– ---> Cu2+(aq)
3
Libretexts. “Electroplating.” Chemistry LibreTexts. Libretexts, August 15, 2020.
https://chem.libretexts.org/Bookshelves/Analytical_Chemistry/Supplemental_Modules_(Analytical_Chemistry
)/Electrochemistry/Electrolytic_Cells/Electroplating.
4
Ibid
5
“Electroplating.” Wikipedia. Wikimedia Foundation, February 26, 2021.
https://en.wikipedia.org/wiki/Electroplating.
2
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