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For a school science project, my teacher asked me to find a reaction that can be slowed down with an inhibitor and film it at home/lab at school. He told not to use lemon on an apple or anything similar because it’s too common. I’ve been looking all over Internet and my kitchen but I can find anything.

Also, I can’t inhibit the reaction of catalysing hydrogen peroxide, because I’m already using this reaction for the other part of the project which is catalysts.

Is there any other inhibitor reactions that actually can be done at home?

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Protease action on jello. Fresh pineapple contains proteases including bromelain which will break down gelatin. If you add fresh pineapple to your gelatin-containing jello it will not set as the gelatin is hydrolyzed. Canned pineapple is heat-treated, which will denature the bromelain. Thus, canned pineapple could serve as your inhibitied sample.

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    $\begingroup$ What is jello ? Why should it set ? What should be the action of protease on gelatin ? Where is the inhibiton here ? $\endgroup$
    – Maurice
    Commented Feb 12, 2022 at 21:30
  • $\begingroup$ @Maurice Jell-o: en.m.wikipedia.org/wiki/Jell-O $\endgroup$
    – Karsten
    Commented Feb 13, 2022 at 13:33
  • $\begingroup$ The protease is “inhibited” (destroyed, really) at high temperature. $\endgroup$
    – Karsten
    Commented Feb 13, 2022 at 13:34
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Here is a fairly simple experiment, essentially involving the replacement of $\ce{H2O2}$ with $\ce{NaOCl}$ (as commonly found in so-called Disinfecting Chlorine Bleach).

This experiment verifies the widely reported sensitivity of common chlorine bleach to sunlight, to quote a guide, for example:

Bleach rapidly degrades in the presence of light and when mixed with water.

I would proceed with two identical portions of the $\ce{NaOCl}$, where one open vessel is stored in the dark, and the other exposed to sunlight, best covered with clear plastic wrap.

Measure the respective comparative ending concentrations of the sodium hypochlorite with the addition of the same amount (but in stoichiometric excess per equation below) of hydrogen peroxide:

$\ce{NaOCl (aq) + H2O2 (aq) -> NaCl (aq) + H2O (l) + O2(g)}$

The mechanics of the photolysis, can perhaps be more likely explained from the photosensitive nature of either minor transition metal presence (from say iron or copper ions including from any incidental dust particle exposure), or just sunlight acting on hypochlorite, or even some hypochlorous acid, per the reaction:

$\ce{OCl- (aq) + H2O (aq) -> HOCl (aq) + OH-}$

based on the reported action of sunlight in this article: "Emerging investigators series: the efficacy of chlorine photolysis as an advanced oxidation process for drinking water treatment", to quote:

The photolysis of hypochlorous acid (HOCl) and hypochlorite (OCl−) produces a suite of reactive oxidants, including hydroxyl radical (˙OH), chlorine radical (Cl˙), and ozone (O3).

where such species would lead to the more rapid degradation of the bleach.

I hope suggestion is of use.

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