Swedish scientist Svante Arrhenius . Earlier in the chapter, reactions were discussed in terms of effective collision frequency and molecule energy levels. A is known as the frequency factor , having units of L mol -1 s -1 , and takes into account the frequency of reactions and likelihood of correct molecular orientation.
The Arrhenius equation allows us to calculate activation energies if the rate constant is known, or vice versa. As well, it mathematically expresses the relationships we established earlier: as activation energy term E a increases, the rate constant k decreases and therefore the rate of reaction decreases.
We can graphically determine the activation energy by manipulating the Arrhenius equation to put it into the form of a straight line. Taking the natural logarithm of both sides gives us:.
The activation energy can also be calculated algebraically if k is known at two different temperatures:. Determine the value of E a given the following values of k at the temperatures indicated:. Skip to content Increase Font Size.
Chapter Learning Objectives To gain an understanding of activation energy. To determine activation energy graphically or algebraically.
Key Takeaways The activation energy can be graphically determined by manipulating the Arrhenius equation. Next: Reaction Mechanisms.
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