Catalysed Decomposition of Hydrogen Peroxide
Three calibration curves and a stoichiometric prediction for the Reactivity Rocket Project
Year 10 Chemistry · Reactivity Rocket Project · Phase 1 Lab 1
Abstract
This investigation measures the rate of catalysed decomposition of hydrogen peroxide using potassium permanganate as a catalyst:
2\text{ H}_2\text{O}_{2\,(aq)} \xrightarrow{\text{KMnO}_4} 2\text{ H}_2\text{O}_{(l)} + \text{O}_{2\,(g)}
Students produce three calibration curves — rate vs [H₂O₂], rate vs [KMnO₄], and rate vs temperature — by measuring the volume of oxygen gas evolved over time. The teacher then demonstrates the same reaction at 35 % H₂O₂ (school lab-stock concentration). Students predict the 35 % rate by extrapolating their 3 % and 6 % calibration line and reconcile their prediction against the teacher’s measurement.
The Arrhenius plot from the temperature calibration yields an apparent activation energy that students compare with the literature value of ≈ 56 kJ/mol for KMnO₄-catalysed peroxide decomposition.
Finally, students combine their measurements into a single stoichiometric prediction: at the measured 35 % H₂O₂ decomposition rate, can a school-scale rig in principle supply the oxygen demand of a 0.5 g/min ethanol burn in the rocket-project test article?
Simulations and supporting materials
Four companion artefacts go with this lab. The first two are interactive simulations that let students explore the reaction at concentrations and configurations not safe to run on the bench. The last two are reference documents that frame the prac in collision-theory and engineering-controls terms.
0-D Thermokinetic Simulation interactive · single-file HTML
What it shows. A well-mixed (zero spatial dimension) reactor model of the KMnO₄ + H₂O₂ system. Slide the temperature, concentration, and volume controls and watch the predicted oxygen-evolution rate and solution temperature evolve in real time. The autocatalytic threshold above ~70 °C is visible as a sharp inflection: keep the bulk temperature below it and the reaction is calm; cross it and the simulation runs away.
Use it to. Build intuition before the prac about why the safety case keeps the bulk temperature below 40 °C.
2-D Hot-Spot Simulation interactive · single-file HTML
What it shows. A two-dimensional cross-section of an unstirred reactor, with a localised hot spot near the catalyst. The bulk temperature stays low while a region near the catalyst climbs 15-20 K above it. The safety margin readout is T_critical (70 °C) - T_peak — when it goes negative, the hot spot has crossed the autocatalytic threshold even though the bulk thermometer would still read “safe”.
Use it to. Understand why stirring and active heat removal are not optional in the prac.
Prac Protocol — Collision Theory in Action document · markdown rendered
A standalone prac protocol covering the same chemistry from a collision-theory perspective, with materials list, method, observations table, analysis prompts, and a set of collision-theory plus engineering-reasoning questions for high-agency students.
VSL Safety Case Sketch — Governed Process document · markdown rendered
A Helios-style specification of the bench prac as a governed chemical reactor: conservation invariants, state envelope, guard predicates, and four-layer assurance pattern. Illustrative — bridges the school-lab safety case to industrial process safety reasoning.
Why the simulations exist
The KMnO₄ + H₂O₂ reaction transitions from a safe demonstration to a dangerous self-sustaining decomposition by progressively removing engineering controls — dilution, stirring, heat removal, volume. The prac runs the safe version. The simulations let students explore what happens as those controls are removed, without ever bringing the unsafe configuration onto the bench. Both artefacts are the same chemistry; the difference is the engineering envelope.
1 Introduction
1.1 Why this experiment matters
Engineering context
This is not a generic rates lab. The same chemistry you measure here drove the Walter rocket (Germany, 1937), the Me 163 Komet interceptor, the Bell Rocket Belt, and the turbopump of the X-1 — the first aircraft to break the sound barrier. All used catalysed decomposition of high-strength hydrogen peroxide as their oxygen source.
Your measurements set the parameters for the Computational Engineering team’s prediction sheet, which the Manufacturing team takes to the vendor for the copper engine.
1.2 Background — the chemistry
Hydrogen peroxide decomposes spontaneously into water and oxygen. Without a catalyst, the reaction is very slow at room temperature: a bottle of 3 % H₂O₂ from a chemist lasts months. With a catalyst, the reaction is dramatically faster.
2\text{ H}_2\text{O}_{2\,(aq)} \longrightarrow 2\text{ H}_2\text{O}_{(l)} + \text{O}_{2\,(g)} \quad \text{(uncatalysed, very slow)}
2\text{ H}_2\text{O}_{2\,(aq)} \xrightarrow{\text{KMnO}_4} 2\text{ H}_2\text{O}_{(l)} + \text{O}_{2\,(g)} \quad \text{(catalysed, fast)}
Potassium permanganate (KMnO₄) provides the manganese in the +7 oxidation state. The reaction with H₂O₂ reduces it to Mn²⁺ in acidic conditions, or to MnO₂ in neutral / slightly alkaline conditions. Either way, the manganese species is regenerated as the reaction proceeds — the defining feature of a catalyst.
1.3 Theory — rate, calibration, extrapolation
The rate of the reaction is the volume of oxygen produced per unit time at the start of the run, before significant H₂O₂ is consumed:
\text{rate} = \left.\frac{dV_{\text{O}_2}}{dt}\right|_{t\to 0} \quad \text{(initial rate)}
We measure this as the slope of the first 30 seconds of a gas-volume-vs-time graph.
A calibration curve maps how the rate changes when one variable is changed and the others are held constant. Three calibration curves together describe the reaction:
- Rate vs [H₂O₂] — fix [KMnO₄] and T; vary peroxide concentration
- Rate vs [KMnO₄] — fix [H₂O₂] and T; vary catalyst concentration
- Rate vs T — fix [H₂O₂] and [KMnO₄]; vary temperature
From the third curve we can extract an activation energy by the Arrhenius relation:
\ln(\text{rate}) = -\frac{E_a}{R}\cdot\frac{1}{T} + \text{const}
A graph of \ln(\text{rate}) on the y-axis against 1/T on the x-axis is a straight line of slope -E_a/R, where R = 8.314\text{ J mol}^{-1}\text{ K}^{-1}.
1.4 Hypothesis
Hypothesis 1. If the concentration of hydrogen peroxide is doubled while the catalyst concentration and temperature are held constant, then the initial rate of oxygen evolution will approximately double, because the rate of a catalysed reaction is approximately first-order in the substrate when the catalyst is not saturated.
Hypothesis 2. Increasing the concentration of KMnO₄ catalyst will initially increase the rate, but eventually the rate will plateau as the catalyst saturates the H₂O₂ available, because rate is set by the limiting reactant once enough catalyst is present.
Hypothesis 3. Increasing the temperature by 10 °C will increase the rate by a factor of approximately two, because reactions with activation energies near 50 kJ/mol roughly double in rate per 10 °C (Arrhenius).
2 Materials and equipment
Per group (student rates calibration)
- 1 × 250 mL borosilicate Erlenmeyer (conical) flask
- 1 × pierced rubber stopper with delivery tube
- 1 × separating funnel (50 mL) with retort stand and clamp
- 1 × 100 mL inverted graduated cylinder over a water trough
- 1 × stopwatch (smartphone is fine)
- 1 × thermometer (0–100 °C) or K-type thermocouple
- 1 × 600 mL water bath beaker + hot plate (Experiment 3 only)
- 1 × labelled waste container (“KMnO₄ / H₂O₂ waste”)
- Goggles + lab coat + nitrile gloves (NOT latex)
- 3 % H₂O₂ (chemist-grade) — 200 mL per group
- 6 % H₂O₂ (chemist-strong-grade) — 200 mL per group
- KMnO₄ solutions at 0.05, 0.10, 0.20, 0.40 M — 50 mL of each per group
- Paper towels (spill clean-up — water only, never near peroxide)
Class (teacher 35 % H₂O₂ demonstration)
- 1 × 250 mL borosilicate Erlenmeyer flask, fresh
- 1 × wide-bore inverted gas collection cylinder
- 35 % H₂O₂ — 50 mL aliquot, dispensed by teacher from oxidiser cabinet
- KMnO₄ solution 0.10 M
- CO₂ extinguisher within 3 m
- Eyewash within 3 m
- 2 m floor tape line for student observation distance
- Wide-bore separating funnel for catalyst delivery
Safety
The risk assessment for this experiment is rated Medium Risk by the laboratory technician. Five controls apply.
- 35 % H₂O₂ is dispensed by the teacher only. Students never open the oxidiser cabinet, never handle the stock bottle, and never transfer 35 % material. Risk codes R-01, R-02, R-03 from the Reactivity Rocket Project safety case.
- No paper towels, gloves, rags, or organic fabric within 1 m of the 35 % rig. Concentrated H₂O₂ + organic = ignition risk. Spills are flushed with water only.
- Nitrile gloves only. Latex degrades on contact with peroxide.
- Goggles always. Splash from KMnO₄ stains skin and clothing indelibly within seconds.
- Wait until the flask is cool to room temperature before decanting. Hot peroxide solutions continue evolving gas. Touch the flask base with a gloved finger as the cool-down check.
Waste H₂O₂ + KMnO₄ solutions: dilute to 10 % strength with water in the labelled waste bottle. Do not drain spent KMnO₄ until the lab technician has confirmed pH 6–8.
3 Method
3.1 Variables
| Type | Variable | How it is controlled or measured |
|---|---|---|
| Independent (Exp. 1) | [H₂O₂] | 3 % vs 6 % stock |
| Independent (Exp. 2) | [KMnO₄] | 0.05, 0.10, 0.20, 0.40 M |
| Independent (Exp. 3) | Temperature | 15, 25, 35, 45 °C (water bath) |
| Dependent | Initial rate of O₂ evolution (mL / s) | Slope of first 30 s of gas-volume-vs-time graph |
| Controlled | Volume of H₂O₂ aliquot | 50 mL per run, measured by the same flask |
| Controlled | KMnO₄ drip rate | 1 drop per second (counted by recorder) |
| Controlled | Same balance, zeroed before each weighing | Tare to 0.00 g |
| Controlled | Same gas-collection cylinder, water level reset | Re-fill the trough between runs |
3.2 Procedure — Experiment 1: rate vs [H₂O₂]
- Assemble the rig. Clamp the Erlenmeyer flask in the fume cupboard. Connect the stoppered delivery tube to the inverted graduated cylinder over the water trough. Confirm the cylinder is filled with water and the meniscus is at the 0 mL line.
- Position the separating funnel. Clamp it above the flask. Close the tap. Pour 50 mL of 0.10 M KMnO₄ into the funnel.
- Pour the peroxide. Carefully add 50 mL of 3 % H₂O₂ to the flask. Seal the stopper.
- Confirm zero. Confirm the gas cylinder reads 0 mL.
- Start the run. Open the funnel tap to deliver KMnO₄ at exactly 1 drop per second. Start the stopwatch when the first drop contacts the H₂O₂ surface.
- Record. At every 10 s read the gas-volume on the cylinder. Continue for 180 s or until the cylinder fills.
- Stop the catalyst. Close the funnel tap. Continue recording until gas evolution slows to less than 1 mL per 10 s.
- Reset and repeat. Decant the flask to the labelled waste container. Rinse the flask with water. Reset the gas cylinder.
- Run the second concentration. Repeat steps 3–8 with 50 mL of 6 % H₂O₂ instead of 3 %.
- Run triplicates. Each concentration should be run three times. The mean of the three initial-rate slopes is the calibration point for that concentration.
3.3 Procedure — Experiment 2: rate vs [KMnO₄]
Same procedure as Experiment 1, but:
- Use 6 % H₂O₂ for every run.
- Vary the KMnO₄ concentration in the funnel through 0.05, 0.10, 0.20, 0.40 M in successive runs.
- Maintain 1 drop/s drip rate every time.
- Three repeats per concentration.
3.4 Procedure — Experiment 3: rate vs temperature
Same procedure as Experiment 1, but:
- Use 6 % H₂O₂ and 0.10 M KMnO₄ for every run.
- Vary the flask temperature by standing it in a water bath at 15, 25, 35, 45 °C.
- Verify the flask + contents temperature with the thermometer or thermocouple immediately before starting the run.
- Three repeats per temperature.
3.5 Teacher demonstration — 35 % H₂O₂
This portion is run by the teacher only. Students record from the 2 m line. Standard Operating Procedure SOP-03 in the Reactivity Rocket Project safety case applies.
The teacher repeats the rig of Experiment 1 with 50 mL of 35 % H₂O₂ and 0.10 M KMnO₄ at 25 °C. The reaction is vigorous and produces hot steam plus oxygen. The Rocket Chemistry team’s Recorder reads gas volume every 5 s from the wide-bore cylinder. The teacher closes the funnel tap after 60 s of gas evolution.
4 Results
4.1 Raw data — Experiment 1: rate vs [H₂O₂]
| Time (s) | 3 % run 1 (mL) | 3 % run 2 (mL) | 3 % run 3 (mL) | 6 % run 1 (mL) | 6 % run 2 (mL) | 6 % run 3 (mL) |
|---|---|---|---|---|---|---|
| 0 | 0 | 0 | 0 | 0 | 0 | 0 |
| 10 | ||||||
| 20 | ||||||
| 30 | ||||||
| 60 | ||||||
| 120 | ||||||
| 180 |
| [H₂O₂] (% w/w) | Mean rate (mL/s) over 0–30 s | Standard deviation across triplicates |
|---|---|---|
| 3 % | ||
| 6 % |
4.2 Raw data — Experiment 2: rate vs [KMnO₄]
| [KMnO₄] (M) | Mean rate (mL/s) | SD across triplicates |
|---|---|---|
| 0.05 | ||
| 0.10 | ||
| 0.20 | ||
| 0.40 |
4.3 Raw data — Experiment 3: rate vs temperature
| T (°C) | T (K) | 1/T (K⁻¹) | Mean rate (mL/s) | ln(rate) |
|---|---|---|---|---|
| 15 | 288.15 | 0.003470 | ||
| 25 | 298.15 | 0.003354 | ||
| 35 | 308.15 | 0.003245 | ||
| 45 | 318.15 | 0.003143 |
4.4 Teacher demonstration result
| Quantity | Value |
|---|---|
| [H₂O₂] | 35 % w/w |
| [KMnO₄] | 0.10 M |
| Temperature | 25 °C |
| Mean rate over 0–30 s (measured) | mL/s |
| Mean rate over 0–30 s (extrapolated from student 3 % + 6 % data) | mL/s |
| Residual (measured − extrapolated) | mL/s |
4.5 Worked example
Demonstration data (made-up but reasonable for school equipment).
Experiment 1, 3 % H₂O₂ trial 1: gas readings of 0, 4, 9, 14, 26, 47, 65 mL at 0, 10, 20, 30, 60, 120, 180 s. Initial slope (0–30 s):
\text{rate}_{3\%} = \frac{14 - 0}{30 - 0} = 0.47 \text{ mL/s}
Experiment 1, 6 % H₂O₂ trial 1 gives a 30 s value of 32 mL:
\text{rate}_{6\%} = \frac{32 - 0}{30 - 0} = 1.07 \text{ mL/s}
The 6 % rate is about 2.3× the 3 % rate. The expected ratio is 2.0× if the reaction is first-order in H₂O₂. The measured 2.3× is within typical experimental scatter for a Year 10 rig — consistent with first-order behaviour.
Linear extrapolation through (0, 0), (3 %, 0.47), (6 %, 1.07) predicts a rate at 35 % of approximately:
\text{rate}_{35\%} \approx \frac{0.47 + 1.07}{2} \times \frac{35}{4.5} \approx 5.9 \text{ mL/s}
The teacher’s measurement at 35 % should fall reasonably close to this value — perhaps ±30 % — given that linear extrapolation across a 10× concentration range is optimistic.
4.6 Observations
Record qualitative observations for each experiment.
Colour of the KMnO₄ on contact with H₂O₂. Does the purple disappear immediately? At what point during the run does fresh KMnO₄ stop being decolourised?
Bubbles in the flask. Where do they form first? Top? Bottom? Where the drops land?
Flask temperature. Touch the flask base with a gloved finger during the run. Cool? Slightly warm? Genuinely hot? (35 % only — expect hot steam, do not touch.)
Cylinder reading rhythm. Does the gas rise smoothly or in pulses? Pulses suggest gas trapped under the stopper.
5 Analysis
5.1 Computing initial rate from the time series
For each run, take the first 30 seconds of gas-volume data. Plot a small graph or use a calculator to find the best-fit slope. The slope is the initial rate in mL/s. Average across triplicates.
Why the first 30 s?
As the reaction proceeds, H₂O₂ is consumed. The rate at t = 60 s is slower than the rate at t = 10 s because there is less peroxide left. We want the rate at the start, when the concentrations are still at their initial values — that is the rate that corresponds to the calibration point.
5.2 Drawing the three calibration curves
Plot:
- Graph 1. Mean rate (mL/s) on the y-axis vs [H₂O₂] (% w/w) on the x-axis. Two points so far; add the teacher’s 35 % point. Draw the best fit through (0, 0) — three concentrations.
- Graph 2. Mean rate on the y-axis vs [KMnO₄] (M) on the x-axis. Four points. Look for a plateau.
- Graph 3. ln(rate) on the y-axis vs 1/T (K⁻¹) on the x-axis. Four points. Should be a straight line.
5.3 Extracting activation energy
From Graph 3, fit a line of best fit through the four points. The slope of the line is -E_a/R:
E_a = -\text{slope} \times R = -\text{slope} \times 8.314 \text{ J mol}^{-1}\text{K}^{-1}
The literature value for KMnO₄-catalysed H₂O₂ decomposition is ≈ 56 kJ/mol. Your measured value should fall within 40–70 kJ/mol for the data to be considered consistent.
5.4 Stoichiometric prediction — the engineering question
Combine your measurements:
\dot{V}_{\text{O}_2,\text{measured}}^{35\%} = ?\text{ mL/min from teacher demonstration}
The ethanol burn in the rocket project’s vendor test article is designed at 0.5 g/min ethanol. The combustion reaction:
\text{C}_2\text{H}_5\text{OH} + 3\text{ O}_2 \longrightarrow 2\text{ CO}_2 + 3\text{ H}_2\text{O}
Stoichiometric oxygen demand:
\dot{V}_{\text{O}_2,\text{demand}} = \frac{0.5 \text{ g/min}}{46.07 \text{ g/mol}} \times 3 \times 22.4 \text{ L/mol} = 0.73 \text{ L/min} = 730 \text{ mL/min}
Required 35 % H₂O₂ flow rate at the measured decomposition rate is:
\dot{V}_{\text{H}_2\text{O}_2,\text{required}} = \frac{730 \text{ mL/min}}{\dot{V}_{\text{O}_2 \text{ per mL of 35 \%}}}
where the O₂ yield per mL of 35 % H₂O₂ is calculated from stoichiometry as ≈ 130 mL O₂ per mL of 35 % solution (working: 1 mL of 35 % at density 1.13 g/mL → 0.40 g H₂O₂ → 0.012 mol → 0.006 mol O₂ × 22.4 L/mol = 132 mL).
Decision rule for the engineering claim
If the required H₂O₂ flow is less than 20 mL/min, the school-scale rig can plausibly supply the ethanol burn. If it is greater, the school chemistry cannot drive the burn and the vendor must use a different oxidiser source (compressed O₂ from cylinder, LOX, or higher-grade peroxide). The Walter rocket of 1937 needed 80 % H₂O₂ for exactly this reason.
6 Discussion
6.1 Did the data support the hypotheses?
For each hypothesis, follow the Claim → Evidence → Reasoning model.
Hypothesis 1 (rate vs [H₂O₂]). Is the 6 % rate approximately double the 3 % rate? Quote the ratio you measured and compare with the expected 2×.
Hypothesis 2 (rate vs [KMnO₄]). Did the rate plateau as catalyst concentration increased? At what catalyst concentration did the gain stop being proportional? Was the catalyst saturated at the 0.40 M condition?
Hypothesis 3 (rate vs T, Arrhenius). What activation energy did your slope give? Is it in the 40–70 kJ/mol range expected for KMnO₄-catalysed H₂O₂ decomposition? If not, name the most likely source of the discrepancy.
The stoichiometric prediction. State whether your reconciliation shows the project’s chemistry can in principle drive the ethanol burn, or whether the vendor will need a different oxidiser. Defend the answer with your computed required H₂O₂ flow rate.
6.2 Sources of uncertainty
Drip rate variability
1 drop per second is a target, not a precise measurement. Drops vary in volume between 0.04 and 0.06 mL. A 50 % variation in catalyst delivery rate maps onto a 10–20 % rate uncertainty in the low-catalyst regime (before saturation).
Gas collection over water
Oxygen partially dissolves in water and the cylinder is not at STP. For typical lab conditions (~25 °C, 101 kPa) the dissolution and volume corrections are 2–5 % and partially cancel; we neglect them.
Self-heating during the run
The reaction is exothermic. Over a long run the flask warms slightly. For the 6 % student case this is < 3 °C and is below the temperature calibration sensitivity. For the 35 % teacher case it is dramatic — hot steam — and confounds the cool-flask Arrhenius extrapolation.
Linear extrapolation to 35 %
The 3 % and 6 % student points are extrapolated linearly to 35 % — a 10× extrapolation. Real-world rates can deviate from linearity at high concentration due to mass-transfer limitations on the catalyst surface. Expect the teacher’s measured rate to fall below the linear extrapolation by 20–40 %.
6.3 Comparison with the rocket project
This experiment’s data feeds two other documents.
- The Computational Engineering team’s prediction sheet — your Arrhenius activation energy parameterises the Rust crate’s
arrhenius_extrapolatefunction, and your stoichiometric flow calculation appears on the public viewer at https://pilot.mentormind.com.au/edu/chemistry-prep/year10/reactivity-rocket-project/computational-engineering-static-test.html - The Manufacturing team’s vendor RFQ — your measurement of the 35 % decomposition rate sets the design oxidiser flow that the vendor’s quote must match.
Your three calibration curves are not a textbook exercise — they set parameters that the rest of the project relies on.
7 Conclusion
State your conclusion in five sentences.
- Restate whether rate increased with [H₂O₂], with [KMnO₄], and with temperature in the directions you predicted.
- Quote your measured activation energy from the Arrhenius fit, with its uncertainty range, and compare to the literature value of approximately 56 kJ/mol.
- State whether the teacher’s 35 % measurement fell within the range your student extrapolation predicted, and name the source of any residual (likely linearity-breakdown, or self-heating).
- State whether the required H₂O₂ flow for a 0.5 g/min ethanol burn is feasible at school-scale (under 20 mL/min) or not.
- Identify the largest source of uncertainty in your experiment and suggest one specific improvement that would reduce it.
8 Extension questions
Q1. Predict whether 80 % H₂O₂ — the concentration used in the Walter rocket — would supply the O₂ demand for a 5 g/min ethanol burn (10× larger than our school-scale design). Show working.
Q2. Suppose the Computational Engineering team’s prediction sheet expects a peroxide decomposition rate of 6.5 mL O₂/s per mL of 35 % H₂O₂. Your measurement is 5.1 mL O₂/s per mL. Reconcile the difference: which of your sources of uncertainty (if any) could account for a 20 % under-measurement?
Q3. The Bell Rocket Belt used 90 % H₂O₂ decomposed by a silver catalyst bed rather than KMnO₄ in solution. Discuss why a solid catalyst bed is preferred at engine scale.
Q4. Sketch the rate-vs-[KMnO₄] graph for an uncatalysed and a catalysed reaction on the same axes. What would the y-axis intercept of the uncatalysed line tell you? Why does the catalysed line not start from zero on the x-axis?
Q5. The literature activation energy for uncatalysed H₂O₂ decomposition is approximately 75 kJ/mol. The catalysed value is approximately 56 kJ/mol. What is the physical interpretation of the 20 kJ/mol difference?
9 References
- Walter, H. (1947). Report on the development of the Walter HWK 109-509 rocket engine (declassified ASME technical memorandum, 1955).
- New South Wales Education Standards Authority. (2018). Science Years 7–10 Syllabus. NESA. Outcomes SC5-7CW (catalysed reactions), SC5-6WS (conducting investigations), SC5-9WS (analysing and communicating).
- Atkins, P. W., & de Paula, J. (2010). Atkins’ Physical Chemistry (9th ed.). Oxford University Press. (Activation energy for KMnO₄-catalysed peroxide decomposition: 54.4 kJ/mol, p. 786.)
- Reactivity Rocket Project, Year 10 Science. (2026). Computational Engineering Static-Test Specification.
pilot.mentormind.com.au/edu/chemistry-prep/year10/reactivity-rocket-project/ - School laboratory risk assessment record. (2026). Risk Assessment: Catalysed H₂O₂ Decomposition — 3 %, 6 %, and 35 % concentrations. Prepared by the Laboratory Technician, May 2026. (On file with the school laboratory.)
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