Question

did the absence of a catalyst have an effect on the outocme of the thermal decomposition of KClO3?

Answer 1

Short answer: Yes — the absence of a catalyst changes the practical outcome.

Explanation:
- A catalyst (commonly MnO2 for KClO3) does not change the stoichiometry — fully heated KClO3 still decomposes to KCl + 3/2 O2 — but it lowers the activation energy and increases the reaction rate.
- Without a catalyst you need higher temperature and/or much longer heating for the same extent of decomposition. Under identical heating conditions you will therefore see less O2 evolved, more unreacted KClO3 left, and a slower/less controlled reaction.
- In practice that can also affect safety and side effects: more vigorous heating to force decomposition can cause local overheating or spattering; if organics are present the larger, uncontrolled oxygen release increases combustion risk.

If you tell me the conditions and observations from your experiment (temperatures, times, gas volumes, masses), I can help interpret whether the absence of a catalyst likely caused the outcome you saw.