Electrochemistry can produce an excellent IB Chemistry scientific investigation because voltage, current, deposited mass, ion concentration, and corrosion rate are all measurable. The strongest IB Chemistry IA electrochemistry topics do not simply compare different metals. They vary one quantitative factor, explain the redox chemistry behind the predicted relationship, and collect enough precise data to support a defensible conclusion.
This guide develops practical ideas involving voltaic cells, electrolysis, electroplating, and corrosion, while explaining suitable variables, data processing, controls, and safety considerations.
What the current IB Chemistry IA requires
The official term for the IA is the scientific investigation. Under the Chemistry course first assessed in 2025, it contributes 20% of the final grade at both SL and HL and has a maximum report length of 3,000 words. It is assessed through four criteria: research design, data analysis, conclusion, and evaluation.
The investigation must answer a student-formulated research question by gathering and analysing data. Students may collaborate in small groups where appropriate and may use similar methodologies, but the independent or dependent variable must differ and each student must collect unique data and submit an individual report. The official IB Chemistry subject brief and IB Chemistry curriculum update provide the current assessment overview.
Before choosing a topic, consult the current RevisionDojo IB Chemistry IA guide. Older online advice may refer to personal engagement, exploration, analysis, evaluation, and communication as five separate criteria. Those belong to the previous assessment model and should not be used as the current rubric.
What makes an electrochemistry investigation effective?
A productive investigation has a continuous independent variable, a quantitative dependent variable, and a chemically justified prediction. For example, varying copper(II) ion concentration across a defined numerical range is usually more analytically useful than comparing five unrelated electrolytes.
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A suitable design should also provide:
A measurable change substantially larger than the instrument uncertainty
A realistic method for controlling temperature, electrode area, time, and distance
Repeated measurements at each independent-variable value
A theoretical model or accepted chemical principle for comparison
Safe quantities and a responsible waste-disposal plan
Five independent-variable levels and three or more repeats per level are often sensible planning targets, but they are recommendations rather than universal IB rules. A preliminary trial should determine whether the proposed range produces stable, distinguishable results.
Voltaic cell IA ideas
A voltaic cell, also called a galvanic cell, converts the energy of a spontaneous redox reaction into electrical energy. Oxidation occurs at the negative anode, reduction occurs at the positive cathode, and ions move through the salt bridge to maintain electrical neutrality.
Possible research question
Independent variable
Measurable output
Important controls
How does CuSO₄ concentration affect the potential difference of a Zn/Cu cell?
Cu²⁺ concentration
Open-circuit voltage
Zn²⁺ concentration, temperature, electrode area, salt bridge
How does temperature affect the potential difference of a Zn/Cu cell?
Temperature
Voltage
Concentrations, immersion depth, equilibration time
How does salt-bridge concentration affect cell performance?
KNO₃ concentration
Voltage or current under fixed resistance
Bridge dimensions, electrode solutions, temperature
How does external resistance affect the power output of a cell?
Resistance
Voltage and current
Electrodes, concentrations, temperature, time after assembly
How does electrode surface area affect current under load?
For concentration investigations, an HL student might compare measured cell potential with a prediction based on the Nernst equation. Do not describe measurements as standard cell potentials unless all relevant standard conditions are satisfied. The IB data booklet lists standard reduction potentials at 298.15 K, but an ordinary classroom cell often differs in concentration, pressure, and temperature.
Voltage should be recorded consistently after a defined equilibration period. Clean electrodes in the same way before every trial because oxide layers and surface contamination can change the reading. The Royal Society of Chemistry’s electrochemical cell practical guidance provides a useful verified model for apparatus and risk assessment.
Electrolysis and electroplating IA ideas
An electrolytic cell uses an external power supply to drive a non-spontaneous redox reaction. The cathode remains the site of reduction and the anode remains the site of oxidation, although the cathode is negative and the anode positive in an electrolytic cell.
Possible research question
Independent variable
Measurable output
Useful processing
How does current affect the mass of copper deposited in a fixed time?
Current
Cathode mass increase
Mass against charge, percentage efficiency
How does electrolysis time affect copper deposition?
Time
Deposited mass
Deposition rate, comparison with Faraday’s law
How does CuSO₄ concentration affect current efficiency?
Cu²⁺ concentration
Actual versus theoretical mass
Percentage current efficiency
How does electrode distance affect current?
Distance
Current at fixed voltage
Resistance or conductivity trend
How does temperature affect electroplating rate?
Temperature
Mass deposited per unit time
Rate and uncertainty
Faraday’s law supplies a clear theoretical model:
m = ItM ÷ nF
Here, m is deposited mass, I is current, t is time, M is molar mass, n is the number of electrons transferred per ion, and F is the Faraday constant. A plot of deposited mass against charge, where Q = It, should be approximately linear if current efficiency remains constant.
Measure electrode mass only after consistent rinsing and drying. Residual electrolyte increases the apparent mass, while vigorous drying or handling may remove loosely attached copper. Recording current continuously is preferable to assuming that the power supply maintains an exact value.
Corrosion is an electrochemical process involving anodic oxidation of a metal and a corresponding cathodic reduction reaction. For iron in aerated water, oxygen reduction and the subsequent formation of hydrated iron oxides make the mechanism more complicated than a single equation.
Promising questions include:
How does sodium chloride concentration affect the corrosion rate of iron?
How does pH affect iron corrosion over a fixed period?
How does temperature affect corrosion in aerated salt water?
How does contact with copper, zinc, or magnesium affect iron corrosion?
How does the concentration of a selected inhibitor affect corrosion rate?
Possible outputs include mass loss per unit area per unit time, Fe²⁺ or Fe³⁺ concentration measured colorimetrically, or oxygen consumption. A simple final mass change can be misleading because rust adds oxygen to the specimen. If corrosion products are removed before weighing, the cleaning procedure must remove rust consistently without significantly attacking the underlying metal.
Standardise alloy type, exposed surface area, surface preparation, solution volume, oxygen exposure, immersion time, and temperature. Avoid nails from mixed manufacturers because differences in coatings and alloy composition can overwhelm the effect of the chosen independent variable.
Data analysis and evaluation
Present raw readings with units, instrument uncertainties, and consistent decimal places. Process the data using means and an appropriate measure of spread, then graph the dependent variable against the independent variable with uncertainty bars where meaningful. The RevisionDojo guide to Chemistry IA data analysis explains these conventions in criterion-focused terms.
Your conclusion should answer the research question quantitatively and compare the observed relationship with chemical theory or reliable reference data. In the evaluation, distinguish random uncertainty from systematic limitations. For example, fluctuating voltage may create scatter, whereas consistently weighing a damp electrode would bias every deposited mass upward.
Avoid generic improvements such as “use better equipment.” State the limitation, explain its likely direction or effect, and propose a feasible correction. A data logger could address changing current, while an insulated water bath could reduce temperature variation.
Safety and environmental responsibility
Every method requires a risk assessment approved by your teacher. Wear eye protection, use small quantities, consult current safety data sheets, and disconnect the power supply before moving electrodes or leads.
Electrolysis of chloride solutions may produce toxic chlorine, while water reduction can produce flammable hydrogen. The RSC’s electrolysis of brine safety guidance stresses that the products can be more hazardous than the starting solution. Avoid chloride electrolysis unless your teacher has approved suitable microscale quantities, ventilation, supervision, and disposal procedures.
Copper, zinc, nickel, silver, and other metal-ion solutions may be harmful and environmentally hazardous. They must be collected and disposed of according to school and local procedures rather than automatically poured into a drain. Low-voltage school power supplies reduce electrical risk, but wet hands, short circuits, hot wires, and electrodes touching remain preventable hazards.
Common mistakes to avoid
Comparing unrelated metals without a quantitative independent variable
Calling every measured voltage a standard cell potential
Assuming the current remains constant during electrolysis
Ignoring electrode cleaning, drying, immersion depth, or exposed area
Measuring rust mass without considering oxygen incorporation
Using too narrow a range for changes to exceed uncertainty
Treating repeats as separate independent-variable values
Listing safety equipment without explaining the underlying risks
The RevisionDojo electrochemistry notes and questions can help strengthen the redox theory behind the investigation. Once a draft is complete, the Chemistry IA Grader can support criterion-based self-review through Jojo AI, although teacher guidance and your own scientific judgement remain essential.
Conclusion
A strong IB Chemistry IA electrochemistry project connects a focused variable to a precise output and an explainable redox model. Voltaic-cell investigations work well for potential difference and power, electrolysis allows comparison with Faraday’s law, and corrosion studies provide meaningful rate data when surface preparation and mass measurement are carefully controlled.
Choose the method only after pilot testing its measurable range, repeatability, and safety. RevisionDojo’s IA guide, electrochemistry resources, exemplars, and Jojo AI feedback tools can then help you refine the design and assess whether the analysis directly answers your research question.
Daniel holds an MSc in Chemistry from Imperial College London and has taught IB Chemistry for over 20 years, including as Head of Chemistry. His focus is on building the conceptual understanding behind each equation rather than rote recall.
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