Chemistry 11–12 · Year 11

Catalysts for the decomposition of hydrogen peroxide: manganese(IV) oxide, potassium iodide and catalase

Module 3: Reactive Chemistry

Practical, model not builtMedium risk

School laboratory, not for home

In a school laboratory, with a teacher supervising, under the school's risk assessment. Not for home.

This site has no interactive model of its own. Where a step or a material names a Concept Studio model, simulation or tool, it has not been built; an external simulation a step names (for example PhET) is not part of this site.

The idea

A catalyst speeds a reaction by providing a pathway with a lower activation energy and is left unchanged; different catalysts lower the barrier by different amounts.

Safety card

Medium riskLearners carry it out, with a teacher supervising

Setting: In a school laboratory, with a teacher supervising, under the school's risk assessment. Not for home.

Hazards

20-volume hydrogen peroxide is an irritant and bleaches skin
vigorous frothing can overflow
hot mixture with liver
manganese(IV) oxide harmful if inhaled

Controls

cylinders in a tray
gloves and eye protection
no more than 25 mL per cylinder
peroxide kept in its brown bottle, cold

Note

NSW Department of Education Chemical Safety in Schools (CSIS) package, 2021 Technical Update: Section 1.7 (risk assessment) and Volume 2 Appendix D (generic assessment advice and DoE chemical categories); record a RiskAssess (riskassess.com.au) risk assessment before the lesson and check the school's hazardous chemical register (CSIS Section 1.9) for local restrictions.

What you need

Hydrogen peroxide 20 volume (about 1.8 mol/L), 25 mL per run, kept cold
Manganese(IV) oxide powder 0.5 g, manganese(IV) oxide granules 0.5 g
Potassium iodide 0.5 g dissolved in 5 mL water
Fresh liver or potato, 2 g, cut small; a second portion boiled for five minutes
250 mL measuring cylinders, six (five catalysts and a no-catalyst control), or a gas syringe with a side-arm flask and data logger
A drop of detergent per cylinder (foam method), tray, stopwatch, thermometer
Balance to 0.01 g for weighing the manganese(IV) oxide before and after

How to do it

Foam method: put 25 mL of peroxide and a drop of detergent in each of six cylinders in a tray; add each catalyst (powder, granules, iodide solution, fresh liver, boiled liver) to five of them as nearly together as possible, leave the sixth as the no-catalyst control, and time the foam to the 200 mL mark.
Gas-volume method: repeat for manganese(IV) oxide powder and for potassium iodide using the syringe, recording volume every 10 s for two minutes; record the temperature rise.
Recover the manganese(IV) oxide by filtering, dry it and weigh it against the starting mass.
Plot volume against time for the two logged runs and compare initial gradients; rank all catalysts.
In the simulation, enter the activation energies for the iodide and catalase pathways and compare the predicted rate ratio with the observed ranking; construct the energy-profile diagram for each pathway.

What you should see

Foam rises fastest with manganese(IV) oxide powder and fresh liver (seconds), more slowly with granules (surface area) and iodide, and barely at all with boiled liver (the enzyme is denatured); a no-catalyst control shows no visible change in the lesson. The full decomposition of 25 mL of 20-volume peroxide would release about 553 mL of oxygen at 25 degrees Celsius; complete decomposition would also release about 4.2 kJ (94.66 kJ per mole of H2O2 from formation enthalpies), enough to warm the 25 g of liquid by up to 40 degrees Celsius, so the flask warms noticeably even though the foam carries much of the heat away. The recovered manganese(IV) oxide weighs close to the starting mass (a little less from losses on the filter paper), showing the catalyst is not used up. A glowing splint relights in the gas.

What changes

What you change: identity and form of the catalyst
What you measure: time to a set foam height, or gas volume against time
What you keep the same: peroxide volume and concentration
starting temperature
catalyst mass
detergent amount

Common misconceptions

Each of these ideas is wrong, and the activity is a chance to test it.

A catalyst gets used up slowly (its mass is unchanged after the reaction).
A catalyst gives the reaction energy (it lowers the barrier; the enthalpy change is unchanged).
Boiling the liver makes a stronger catalyst (heat denatures catalase and the activity is lost).

Curriculum references

The NSW syllabus outcomes and Australian Curriculum v9 codes this activity supports. They are references, not a verified or complete curriculum alignment.

Chemistry Stage 6 Syllabus (2017), NESA; the current syllabus, taught in 2026 (codes read from the syllabus document)CH11-10 CH11/12-3
Chemistry Stage 6 Syllabus (2017), NESA; the current syllabus, taught in 2026 (codes read from the syllabus document); the Module 4 knowledge outcome, cited on a Module 3 entry because Module 4, not Module 3, carries the content points on the role of catalysts and on energy profile diagramsCH11-11
Chemistry Stage 6 Syllabus (2017), NESA; the current syllabus, taught in 2026 (codes read from the syllabus document); a Working Scientifically outcome not among those the syllabus targets in Module 3, which it allows in any moduleCH11/12-5
Chemistry 11-12 Syllabus (2025), NESA; implemented from 2028, not yet taughtCH-11-03 CH-11WS-03 CH-11WS-05
Australian Curriculum v9No Australian Curriculum v9 code is listed.

Sources

The pages the author read to write this activity.

All Concept Studio activities