# What are catalysts?

Jul 16, 2018

catalysts alter the rate of reaction

#### Explanation:

Catalysts are substances which negatively or positively effect the rate of reaction by altering the threshold energy(Minimum energy required by colliding molecules to undergo a chemical change) and thus activation energy(Minimum energy required by reactant molecules to form activated complex) of the reaction without taking part in it.

They do this by providing an alternate pathway that has lesser or greater threshold energy then the original path.

Positive catalysts increase the rate of reaction by decreasing the threshold energy and hence the activation energy.All biological catalysts(enzymes) are examples of positive catalysts.

Negative catalysts decrease rate of reaction by increasing the threshold energy and hence the activation energy of the reaction.Phosphoric acid in decomposition of ${H}_{2} {O}_{2}$ , alcohol in oxidation of chloroform($C H C {l}_{3}$) and biological inhibitors are some examples.