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Write Arrhenius equation. What is the ${E_a}$ in the equation called?

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Last updated date: 11th Jun 2024
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Answer
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Hint: The Arrhenius equation, derived and proved by Swedish scientist Svante August Arrhenius, is an empirical equation relating the temperature dependence of reaction rates. It helps us to obtain reaction rate at a particular temperature. According to the Arrhenius model, each reaction needs a threshold energy for the reaction to begin, known as the activation energy.

Formulas used: $k = A{e^{\dfrac{{ - {E_a}}}{{RT}}}}$
Where $k$ is the rate constant, $A$ is a constant known as the pre-exponential factor, ${E_a}$ is the activation energy for the reaction (in the same units as $RT$), $R$ is the universal gas constant and $T$ is the absolute temperature (in kelvin)

Complete step by step answer:
According to Arrhenius, the relationship between rate constant of a reaction and the absolute temperature at which it takes place is given by:

$k = A{e^{\dfrac{{ - {E_a}}}{{RT}}}}$

Where $k$ is the rate constant, $A$ is a constant known as the pre-exponential factor, ${E_a}$ is the activation energy for the reaction (in the same units as $RT$), $R$ is the universal gas constant and $T$ is the absolute temperature (in kelvin)
As we can see from the equation, the term ${E_a}$ denotes the activation energy of the reaction, which is the minimum energy that must be possessed by the reactants at a specific temperature for the reaction to occur.

Note: The activation energy is also known as the threshold reaction, and if the reactants have energies lower than this value, reaction will not occur. The role of catalysts in reactions is to lower this activation energy, so that the reaction can take place easily. Note that the pre-exponential factor is a constant for a given reaction, and does not change even if the temperature is changed.