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The Arrhenius Equation

The Arrhenius Equation. AP Chemistry Unit 8 Kinetics. The Arrhenius Equation. Used to describe the temperature dependence of the rate constant. k = rate constant A = frequency factor for collisions Ea = activation Energy (J/mol) R = Gas constant (8.3145 J/Kmol) T = Temperature in Kelvin.

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The Arrhenius Equation

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  1. The Arrhenius Equation AP Chemistry Unit 8 Kinetics

  2. The Arrhenius Equation • Used to describe the temperature dependence of the rate constant k = rate constant A = frequency factor for collisions Ea = activation Energy (J/mol) R = Gas constant (8.3145 J/Kmol) T = Temperature in Kelvin

  3. Determining Ea Determining the rate law constant at various temperatures gives a straight line with slope that will give us the Activation Energy, Ea

  4. Plotting the natural log of k vs. the reciprocal if Kelvin gives a straight line with a slope of -2.19 x 104. What is the activation energy for the reaction? Slope = -Ea/R -2.19 x 104K = -Ea/8.3145J/Kmol Ea = 1.82 x 105 J/mol = 182 kJ/mol

  5. Equation to Calculate “k” at different temperatures • k1 = Ea [1/T2 – 1/T1] • k2 R ln

  6. What is the rate constant at T = 350K if at 298K, k = 3.55 x 10-2/sec and the Ea is 49.7kJ/mol? Rearrange the equation to lnk1 – lnk2 = Ea[1/T2 – 1/T1] R ln(3.55 X 10-2) – lnk2 = (49.7 x 103/8.3145) [ 1/350 – 1/298] -3.33822 - lnk2 = -2.9802 lnk2 = -0.35802 k2 = e -0.35802 k2 = 0.699 sec-1

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