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 ( J/Kmol) T = Temperature in Kelvin

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

Plotting the natural log of k vs. the reciprocal if Kelvin gives a straight line with a slope of x What is the activation energy for the reaction? Slope = -Ea/R x 10 4 K = -Ea/8.3145J/Kmol Ea = 1.82 x 10 5 J/mol = 182 kJ/mol

Equation to Calculate “k” at different temperatures k 1 = E a [1/T 2 – 1/T 1 ] k 1 = E a [1/T 2 – 1/T 1 ] k 2 R k 2 R ln

What is the rate constant at T = 350K if at 298K, k = 3.55 x /sec and the E a is 49.7kJ/mol? Rearrange the equation to lnk 1 – lnk 2 = Ea[1/T 2 – 1/T 1 ] R ln(3.55 X ) – lnk 2 = (49.7 x 10 3 /8.3145) [ 1/350 – 1/298] lnk 2 = lnk 2 = k 2 = e k 2 = sec -1