Activation energy of any chemical reaction can be calculated if one knows the value of
Correct Answer :
rate constant at two different temperatures
Solution :
The correct answer is rate constant at two different temperatures.
To understand why, we can refer to the Arrhenius equation, which describes the quantitative relationship between the rate constant of a chemical reaction and the absolute temperature:
where:
• is the rate constant of the reaction,
• is the pre-exponential factor (or frequency factor),
• is the activation energy,
• is the universal gas constant, and
• is the absolute temperature (in Kelvin).
Taking the natural logarithm of both sides of the Arrhenius equation:
If we determine the rate constant at two different temperatures, say and , the corresponding rate constants are and respectively. Writing the logarithmic form for both conditions:
and
By subtracting the equation for from the equation for , we eliminate the unknown pre-exponential factor :
Simplifying the relationship:
Converting the natural logarithm (ln) to base-10 logarithm (log):
From this final integrated expression, we can conclude that the activation energy () can be calculated if we know the rate constant at two different temperatures.
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