1. Effect of temperature on reaction rate:
⇒ As the temperature increases, the average energy of the reaction increases, hence rate of reaction increases.
⇒ As a common rule, for every 10° rise of temperature, the rate of reaction will increase by 2 (or) 3 times of initial value.
⇒ According to Arrhenius concept:
η = η₀ e -Eₐ/RT
η₀ = total number of molecules
η = total number of molecules activated
Eₐ = Activation energy
It can be written in the following way.
K = A e -Eₐ/RT
K = Rate Constant of reaction
log K₂/K₁ = -Eₐ/R ([1/T₂] – [1/T₁])
2. Effect of catalyst on reaction rate:
⇒ A catalyst alters the reaction velocity by changing the activation energy by changing the reaction mechanism, without getting consumed during the reaction.
⇒ The physical state of the
catalyst may or may not change.
⇒ A catalyst works by providing an alternate path to the reaction
a. Positive catalysts: A catalyst which increases the rate of reaction is called positive catalyst. Such catalyst decreases activation energy by accepting a smaller path, so rate of reaction is increased.
b. Negative catalysts (Inhibitors): A catalyst which decreases or retards the rate of reaction is called negative catalysts.
Eg:
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