Negative Catalyst

A catalyst is any substance (or material), when it is added in the reaction then due to their presence in the reaction, the speed of the reaction is altered. And this reaction in which a catalyst is present, is called as "catalytic reaction". This phenomena is called "Catalysis". Thus, these substances can increase or decrease the rate of chemical reaction and negative catalyst is a type of catalyst which decreases the rate of chemical reaction.

Negative Catalysts
The catalyst which reduces the rate of reaction by increasing the activation energy, is called 'Negative catalysts' and this phenomena is called as "Negative catalysis". Remember if we increased the activation energy then the path through which a reactant is converted into product, also increases. And thus, the rate of reaction decreases. Let's have a look some examples related to negative catalysts;
➤ Phosphoric acid as negative catalysts in the definition of hydrogen peroxide;
         2H₂O₂ (H₃PO₄ as catalyst) ➝ 2H₂O + O₂
➤ Oxidation of Na₂SO₃ in presence of alcohols used ethyl alcohol as negative catalysts;
          Na₂SO₃ (C₂H₅OH as catalyst)➝ Na₂SO₄
➤Acetanilide/glycerine also acts as negative catalyst in decomposition of H₂O₂.
➤T.E.L.(Tetra Ethyl Lead) an anti-knocking substance is added to petrol to decrease the ignition of petrol vapours. Here, T.E.L. behaves as negative catalyst.


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