Chemistry

At 425°C, a reaction has a rate constant of 7.7 x 10–4 s–1 and has an activation energy of 275 kJ mol–1. What is the frequency factor?

The answer is 2.9 x 1017 s–1 , I need help with working out I used arrhenius equation and rearranged for A = K /e^(-Ea/RT). My answer comes out too big.

  1. 👍 0
  2. 👎 0
  3. 👁 39
asked by jessica
  1. As I understand it, the ‘frequency factor’ does not have units. What you are showing in the posted question is ‘rate constant’ calculated from the Arrhenius Equation. The Arrhenius Equation is derived from the frequency factor. From the KM Theory f = e¯∆E/RT and represents the fraction of molecular collisions having energy values greater than the activation energy. In the posted problem, if ∆E = 275 Kj/mole = 2.75 x 10ˢ J/mole, T = 275⁰C = 698 K and R = 8.314 J/mol·K => ∆E/RT = [(2.75 x 10ˢ J/mole)/(8.314 J/ mol·K)(698 K)] = 47.39. All units cancel out. Substituting into f = e¯∆E/RT => f = e^-(47.39) = 2.63 x 10¯²¹. Also, this type problem usually comes with a couple of temperature values which serve to illustrate – after calculation – the significant increase in number of collisions having energy values greater than the activation energy. Compare frequency at 698 K to frequency at 708 K, a 10⁰ increase in temperature. Frequency at 708 K = e^-(46.72) = 5.13 x 10¯²¹. This represents about a 2-times increase in reaction rate. Hence, the generalization ‘For every 10⁰C increase in temperature, the reaction rate doubles … b/c frequency of collisions greater than the activation energy doubles.

    1. 👍 0
    2. 👎 0
    posted by Dr Rebel

Respond to this Question

First Name

Your Response

Similar Questions

  1. chemistry

    The activation energy of a reaction is typically determined by calculating the rate constant for the reaction at two temperatures and then manipulating the Arrhenius equation. If you determine the reaction rate constants for a

    asked by danny on February 14, 2015
  2. help help help chemistry

    why will no one answer this question? For a one step reaction, the activation energy for the forward reaction is 40.0 kJ/mol and the enthalpy of reaction is -20.0 kJ /mol. Which statement below is true? a. The activation energy of

    asked by john117 on February 27, 2012
  3. chemistry

    For a one step reaction, the activation energy for the forward reaction is 40.0 kJ/mol and the enthalpy of reaction is -20.0 kJ /mol. Which statement below is true? a. The activation energy of the forward reaction would be

    asked by john117 on February 27, 2012
  4. chemistry

    For a one step reaction, the activation energy for the forward reaction is 40.0 kJ/mol and the enthalpy of reaction is -20.0 kJ /mol. Which statement below is true? a. The activation energy of the forward reaction would be

    asked by bob on February 24, 2012
  5. chemistry

    For a one step reaction, the activation energy for the forward reaction is 40.0 kJ/mol and the enthalpy of reaction is -20.0 kJ /mol. Which statement below is true? a. The activation energy of the forward reaction would be

    asked by bob on February 25, 2012
  6. Chemistry

    For a one step reaction, the activation energy for the forward reaction is 40.0 kJ/mol and the enthalpy of reaction is -20.0 kJ /mol. Which statement below is true? a. The activation energy of the forward reaction would be

    asked by Mohamed on March 1, 2012
  7. chemistry

    The activation energy for the reaction in which CO2 decomposes to CO and a free radical oxygen atom, O, has activation energy of 460 kJ mol^-2. The frequency factor is 2 x 1011 s^-1. What is the rate constant for this reaction at

    asked by Massiel on March 20, 2011
  8. CHEm

    Which term best describes the measure of the increase in the concentration of a product per unit time? activation energy, kinectics, reaction reaction rate, reaction time im stuck i think its activation energy can someone confirm

    asked by sue on April 28, 2007
  9. chemistry

    Doing review for an exam and I can't find how to do this problem in my notes. 2 SO2 + 2 Cl2 -----> 2 SOCl2 + O2 from a previous problem I solved: rate=k[SO2]^2[Cl2] k = 467.666666... or in sig. figs 467 Energy reaction: T= 25 C

    asked by energy diagram on July 14, 2011
  10. chemistry

    Doing review for an exam and I can't find how to do this problem in my notes. 2 SO2 + 2 Cl2 -----> 2 SOCl2 + O2 from a previous problem I solved: rate=k[SO2]^2[Cl2] k = 467.666666... or in sig. figs 467 Energy reaction: T= 25 C

    asked by energy diagram on July 13, 2011

More Similar Questions