What is Arrhenius: Definition and 39 Discussions

In physical chemistry, the Arrhenius equation is a formula for the temperature dependence of reaction rates. The equation was proposed by Svante Arrhenius in 1889, based on the work of Dutch chemist Jacobus Henricus van 't Hoff who had noted in 1884 that the van 't Hoff equation for the temperature dependence of equilibrium constants suggests such a formula for the rates of both forward and reverse reactions. This equation has a vast and important application in determining rate of chemical reactions and for calculation of energy of activation. Arrhenius provided a physical justification and interpretation for the formula. Currently, it is best seen as an empirical relationship. It can be used to model the temperature variation of diffusion coefficients, population of crystal vacancies, creep rates, and many other thermally-induced processes/reactions. The Eyring equation, developed in 1935, also expresses the relationship between rate and energy.

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  1. Bernadette

    B Exploring Entropy with Svante Arrhenius' Salt Water Experiment

    Hello Sorry for my English... We approach slowly (in a quasi-reversible way) an electrical charge of a glass of salt water. Some ions arrange themselves in the glass. What can we say about entropy of this transformation? Bernadette PS: My reflection comes from reading an old physics book...
  2. Tymothee Waldner

    Do Different Temperatures Affect Enzyme Activity in a Parabolic Arrhenius Plot?

    Hi, I am currently doing a kinetic study on an enzyme catalysed reaction and plotting the Arrhenius graph I got a parabola. My idea is to take the derivative at each point, meaning there would be different activation energies depending on the temperature, guessing it is due to enzymes dependency...
  3. M

    Rate constant calculation Using the Arrhenius equation

    Homework Statement A reaction has a rate constant of 0.0117/s at 400.0 K and 0.689/s at 450.0 K. What is the value of the rate constant (to 1 decimal place) at 538 K? Homework Equations ln k= ln A-E[a]/RT The Attempt at a Solution I'm not sure how to approach this problem, although I know...
  4. O

    Arrhenius Equation and pseudo isotherms

    Hey, I'm doing an experiment where I run a reaction at three different microwave powers to determine if there is any effect beyond the standard temperature ramp rates. If I know how long it takes the reaction to go from 260 C to 280 C in each of these cases, is there any possible way to extract...
  5. M

    MHB HSO4^-1 as Arrhenius & Bronsted-Lowry Acid/Base

    write down 2 equations to show how the HSO4^-1 ion can behave as a arrhenius acid and bronsted lowry base i know if its a arrhenius acid it dissociates in water to produce hydrogen ions so HSO4^-1 +h20 goes to SO4^-2 and the hydronium ion. is this right? i don't know how to show if its a...
  6. F

    Arrhenius Equation: Can We Substitute k with 1/t?

    I know the Arrhenius equation is k=Ae^-Ea/RT The rate constant k is directly proportional to 1/t (t stands for the time for the reaction to reach a point) So I wonder if we can substitute k by 1/t in the Arrhenius equation to become 1/t=Ae^-Ea/RT ? Thanks a lot
  7. hernando Jose

    Is there a table of Viscosity vs Temp for metals (liquid state)?

    [moderator's note: I've decided to allow this question despite the lack of the formatting template - gneill] ladies and gentlemen, my most cordial greeting to you. i write here cause i need a viscosity vs Temperature data table about liquid metals (more specific pure Post-transition metal...
  8. A

    Activation energy of parallel reaction

    Well,I know that the activation energy of a parallel reaction can be determined by the arrhenius equation as (e1k1+e2k2)/(k1+k2) where e1,k1 and e2,k2 are the activation energies and rate constants for the two reacations.now consider the reaction A》B,and A》C since at every instant the reacted...
  9. J

    What's the difference between an Arrhenius acid and a Bronsted-Lowry acid?

    They both produce H+ right? How do I tell the difference in a reaction?
  10. P

    Understanding Arrhenius Plots: ln(rate) vs 1/T for Determining Activation Energy

    I have been noticing that in some cases that Arrhenius plots are sometimes plotted ln(rate) vs 1/T as opposed to ln(k) vs 1/T to find activation energy especially in hetereogeneous catalysis. Isn't the Arrhenius law k=A*exp(-Ea/(R*T))? why can ln(rate) also be plotted vs T^-1 to find...
  11. B

    Arrhenius equation and rate of change

    I wanted to see how the rate of change of rate constant with temperature (dk/dT) changes with activation energy. I tried to do this with differentials: k=A*e-EA/RT so \frac{dk}{dT} = \frac{A E_A \cdot e^{-\frac{E_A}{RT}} } {RT^2} and then \frac{d(\frac{dk}{dT})}{dE_A} = A \cdot...
  12. C

    Solving Kinetics & Arrhenius Equation: Find A & Ea

    Homework Statement The activation energy and Arrhenius paramter can be found from its temperature dependence the Arrhenius equation k=Aexp(-Ea/RT) --> lnk=lnA - Ea/RT Given data is 5 temperatures with their corresponding k values Q1) From this data calculate A and Ea q2) Here A has...
  13. F

    Calcualting Activation Energy using Arrhenius equation and plot

    This is part of a lab report so not sure if the template agrees with what I am asking but basically using the Arrhenius equation in the form of ln(k)=ln(A)+(\frac{-E_a}{R})(\frac{1}{T}) I plotted a straight line graph of ln(k) vs 1/T and found the gradient to be -5525. Its the units that are...
  14. K

    Need to find the pre-exponential factor within Arrhenius equation

    1. Within direct simulation Monte Carlo (DS3V) I am having problems determining the pre-exponential factor inside of the Arrhenius equation. I have all fields of data other than that and the reaction rate constant which I cannot find. This is for a protium medium with neutrons being inserted...
  15. M

    Arrhenius vs. Le Chatelier battle

    Hello, In my class we were talking about the design of an ammonia reactor, and there is a battle between arrhenius and le chatelier for getting the highest conversions. Apparently the two are at odds with each other as far as getting the highest conversion of ammonia. I am confused how the...
  16. M

    Universal Gas constant and arrhenius equation

    Hello, I am curious as to how the Universal Gas Constant, R, is important with regards to the rates in solids? It is in the Arrhenius Equation
  17. Saitama

    Arrhenius Equation for parallel reaction

    Homework Statement For the two parallel reactions ##A \stackrel{k_1}{\rightarrow} B## and ##A \stackrel{k_2}{\rightarrow} C##, show that the activation energy ##E'## for the disappearance of ##A## is given in terms of activation energies ##E_1## and ##E_2## for the two paths by...
  18. P

    Arrhenius plot and activation energy

    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...
  19. J

    The Arrhenius equation question

    When finding the activation energy, which equation is the correct one: ln(k2/k1)=-Ea/R * (1/T2-1/T1) or ln(k1/k2)=Ea/R * (1/T2-1/T1) Notice k1/k2 in the second equation. As well as the -Ea instead of Ea Thanks
  20. A

    Eyring polanyi vs arrhenius equation

    They both are derived from same kinetic theory of gases, but I've heard that eyring polanyi equation is more advantageous over the arrhenius equation. Why do you think that is the case?
  21. E

    Arrhenius equation problem - converting equations

    Hi there I've been trying to work this out and didn't quite succeed, so I'm hoping someone might help me out a bit. I've been using the Arrhenius equation to calculate reaction rates at 2 temperatures, so I took the integral and got k2/k1 = e^(Ea/R(1/T1 - 1/T2)) This paper I've been...
  22. B

    Exponent value in Arrhenius Equation

    This may be a pretty dumb question, but how is it that as the exponent value of e decreases, the rate k increases? This seems counter-intuitive, and when I enter values for e into my calculator and compare them, the higher exponents (e.g. 50 vs. 20) give higher results.
  23. Saitama

    Why is the Arrhenius plot for the rate constant different from y=e-1/x?

    Homework Statement This isn't a homework question but this thing is disturbing from a long time. I attended a class on Arrhenius equation and its plots. One of the plots is disturbing me from long which is the plot between k vs T. Arrhenius equation:- k=Ae^{-\frac{E_a}{RT}} k->Rate constant...
  24. M

    Can I Use Rates Instead of Rate Constants in an Arrhenius Plot?

    Heres the question: http://img215.imageshack.us/img215/1185/screenshot5xq.png Kinetics is probably my weakest area in chemistry so I'm struggling. To find the shelf life, I need to use the Arrhenius equation but I don't know the activation energy Ea or the A constant. So I converted 2 those...
  25. P

    Finding the Temperature for K to Equal A: An Arrhenius Equation Problem

    Homework Statement At what temperature does K = A? Homework Equations k= Ae^{-Ea/RT} The Attempt at a Solution In order for K to equal A, then e=0. But at what temperature can e=0? The temperature can't be 0, because that would be impossible. Any help is appreciated?
  26. S

    Heat diffusion with arrhenius source

    Homework Statement a material occupies -L < x < L and has uniform ambient temperature T_a. A chemical reaction begins within the body leading to the 1-d heat equation: pc \frac {\partial{T}}{\partial{t}} = k \frac {\partial^2{T}}{\partial{x^2}} + pQAe^\frac{-E}{RT} with BC and IC T(+/-...
  27. H

    On Arrhenius plots in cyclic voltammetry

    I am doing a catalytic study on my Pt nanoparticles. My experiment set-up is a three-electrode cell with sulfuric acid as electrolyte for methanol electrooxidation reaction. Now, i want to calculate the apparent activation energy and for that I need to get the voltammograms at various...
  28. P

    Rate of reaction, rate constants, and Arrhenius' Equation

    Homework Statement The effect of temperature on the rate of a reaction was studied and the following data obtained: k (s-1) T (°C) 3.06×10-4 10 4.84×10-4 16 6.50×10-4 20 1.40×10-3 31 2.87×10-3 42 4.16×10-3 48 5.94×10-3 54 7.92×10-3 59 It is known that...
  29. Topher925

    What is the meaning of Arrhenius behavior?

    I'm always reading about reactions or physical phenomena having Arrhenius behavior. But I can't figure out what that means. I obviously did a search and I learned a lot about the physical chemist Arrhenius, but nothing about what the adjective named after him means.
  30. F

    Chemistry- two point Arrhenius Equation (miscalculation?)

    Chemistry- two point Arrhenius Equation (miscalculation??) Homework Statement At 25 degrees celsius, the first-order rate constant for a reaction is 2.0 x 10^3 s^-1. The activation energy is 15.0 kJ/mol. what is the value of the rate constant at 75 degrees celsius. T1= 298.15 K T2=...
  31. J

    What is your opinion about Arrhenius' announcement?

    At the ceremony of awarding Nobel prizes, Svante Arrhenius said as following. "Most discussion centers on his theory of relativity. This pertains essentially to epistemology and has therefore been the subject of lively debate in philosophical circles." I agree with Arrhenius what is...
  32. V

    Arrhenius Equation - Chemical Kinetics

    Hello everyone, I am having trouble with determining where I erred in the following exercise. If someone could point out my mistake, I would appreciate the help. Thank you! --- 1. The decomposition of N2O5 has an activation energy of 103 kJ/mol and a frequency factor of 4.3E13 s^-1 . What...
  33. F

    Arrhenius equation (chemistry)

    Homework Statement The activation energy for the reaction N2O(g) --> N2(g) + O(g) is 250 kJ/mol. If the rate constant is 3.4 s–1 at 1050 K, at what temperature will the rate constant be one thousand times smaller? The correct answer is : 846 K Homework Equations Arrhenius equation...
  34. B

    Finding Activation Energy From Arrhenius Plot

    Homework Statement For a lab, I need to find the activation energy of an experiment from plotting the Arrhenius plot. I have the half-life time of the reaction at various temperatures. Homework Equations -Temperature (K) 318 322 327 331 338 -ln k -6.17 -5.89 -5.65 -5.33...
  35. F

    Solving Arrhenius Eqn: Double Reaction Rate at 10°C

    Homework Statement A common rule of thumb is that temperature 10 degrees C for many reactions will double the reaction rate. Derive under what conditions this is true.Homework Equations ln(k) - ln(2k) = (-Ea/R) [(1/T1)-(1/T2)]The Attempt at a Solution I know I have to start off by plugging in...
  36. P

    Example of a substance that is a Bronsted-Lowry, but not Arrhenius

    Could someone give and example of a substance that is a Bronsted-Lowry base, but not an Arrhenius base..
  37. A

    Is Releasing Hydrogen Ions the Defining Characteristic of Arrhenius Acids?

    An Arrhenius acid a) in an ionic compound that contains hydrogen atoms b) produces an aqueous solution whose pH is greater than 7 c) releases hydrogen ions in aqueous solution d) is always a neutral molecule I know that c) is true and d) is false. However, I don't know if a) and b)...
  38. A

    Acids & Bases: Arrhenius, Brønsted-Lowry, and Lewis

    Problem: Complete Table 1 by noting how each theory defines acids and bases. Also, list chemical reactions that demonstrate the action of each acid or base. For example, in the reaction HA --> H+ + A-, HA acts as an Arrhenius acid. Firstly, I'd like to check my answers for the chemical...
  39. S

    Arrhenius equations; A2 Chemistry coursework

    Hello everyone, I'm in my last year of A-level chemistry here in the UK, and am currently writing up my chemistry coursework. Its a project I was given on the kinetics of the reactions between magnesium ribbon and several different acids (I wanted to explore some much more exciting fields...