Arrhenius plot and activation energy

In summary, the conversation is about determining the activation energy of donor levels using a formula involving the absorption of a mono-crystal sample at different temperatures. The formula mentioned is D=D0exp(-Ea/kT), and the desired activation energy is 0.043eV. However, there seems to be a problem with getting the correct answer and the speaker is seeking help in deriving the formula. Another person suggests checking for errors in the data and the units used.
  • #1
prehisto
115
0
Hi,guys.
I m trying to determine activation energy of donor levels .
So i have measured absorption at different temperatures of my sample (mono-crystal)

And I have plotted ln(optical density) vs 1/T(K).
And I want to calculate activation energy useing
D=D0exp(-Ea/kT)

In plot above (picture) Eactivation should be 0.043eV

The problem is that I can't get the right answer.
Could someone help me,and derive the mentioned formula above for Ea determination? Maybe I am doing it wrong.
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  • #2
Hi prehisto,

First the scatter in your data should make a large error bar. What is the 95% confidence range of this fitted activation energy?

Second, I would check things like natural log v.s. decimal log and the units of Boltzmann constant, just the basic stuff.
 
  • #3
I agree, it makes a large error bar. But in this case it does not matter . This is an example for which i know the result ( for this particular liner fitting).

i have checked logarithms and Boltzman const.

Is this the correct formula?
 

What is an Arrhenius plot?

An Arrhenius plot is a graph that shows the relationship between the logarithm of the rate constant and the reciprocal of the temperature for a chemical reaction. It is typically used to determine the activation energy of a reaction.

What is activation energy?

Activation energy is the minimum amount of energy required for a chemical reaction to occur. It is often represented by the symbol Ea and is a measure of the difficulty of breaking and forming chemical bonds in a reaction.

How is activation energy calculated from an Arrhenius plot?

To calculate the activation energy from an Arrhenius plot, one must determine the slope of the line on the graph. The slope is equal to -Ea/R, where R is the gas constant. Therefore, the activation energy can be calculated by multiplying the slope by -R.

What factors can affect the activation energy of a reaction?

The activation energy of a reaction can be affected by several factors, including the concentration of reactants, temperature, and the presence of a catalyst. Generally, a higher temperature or the presence of a catalyst can lower the activation energy and make the reaction occur more quickly.

How is the Arrhenius equation used in chemical kinetics?

The Arrhenius equation is used in chemical kinetics to describe the relationship between the rate constant of a reaction and temperature. It states that the rate constant is equal to A*e^(-Ea/RT), where A is the frequency factor, Ea is the activation energy, R is the gas constant, and T is the temperature in Kelvin.

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