Lesson plan
Arrhenius plot
In chemical kinetics, an Arrhenius plot displays the logarithm of a reaction rate constant, ordinate axis) plotted against reciprocal of the temperature abscissa). Arrhenius plots are often used to analyze the effect of temperature on the rates of chemical reactions. For a single rate-limited thermally activated process, an Arrhenius plot gives a straight line, from which the activation energy and the pre-exponential factor can both be determined. The Arrhenius equation can be given in the form: k = A \exp\left(\frac{-E_\text{a}}{RT}\right) = A \exp\left(\frac{-E_\text{a}'}{k_\text{B}T}\right) where: * k = rate constant * A = pre-exponential factor * E_\text{a} = (molar) activation energy * R = gas constant, ( R=k_\text{B} N_\text{A} , where N_\text{A} is the Avogadro constant). * E_\text{a}' = activation energy (for a single reaction event) * k_\text{B} = Boltzmann constant * T = absolute temperature The only difference between the two forms of the expression is the quantity used for the activation energy: the former would have the unit joule/mole, which is common in chemistry, while the latter would have the unit joule and would be for one molecular reaction event, which is common in physics. The different units are accounted for in using either the gas constant R or the Boltzmann constant k_\text{B} .…
Article summary
In chemical kinetics, an Arrhenius plot displays the logarithm of a reaction rate constant, ordinate axis) plotted against reciprocal of the temperature abscissa). Arrhenius plots are often used to analyze the effect of temperature on the rates of chemical reactions. For a single rate-limited thermally activated process, an Arrhenius plot gives a straight line, from which the activation energy and the pre-exponential factor can both be determined. The Arrhenius equation can be given in the form: k = A \exp\left(\frac{-E_\text{a}}{RT}\right) = A \exp\left(\frac{-E_\text{a}'}{k_\text{B}T}\right) where: * k = rate constant * A = pre-exponential factor * E_\text{a} = (molar) activation energy * R = gas constant, ( R=k_\text{B} N_\text{A} , where N_\text{A} is the Avogadro constant). * E_\text{a}' = activation energy (for a single reaction event) * k_\text{B} = Boltzmann constant * T = absolute temperature The only difference between the two forms of the expression is the quantity used for the activation energy: the former would have the unit joule/mole, which is common in chemistry, while the latter would have the unit joule and would be for one molecular reaction event, which is common in physics. The different units are accounted for in using either the gas constant R or the Boltzmann constant k_\text{B} .…
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Discussion questions
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