View Single Post
physics120
#1
Sep25-09, 06:39 PM
P: 34
1. The problem statement, all variables and given/known data

The effect of temperature on the rate of a reaction was studied and the following data obtained:

k (s-1) T (C)
3.0610-4 10
4.8410-4 16
6.5010-4 20
1.4010-3 31
2.8710-3 42
4.1610-3 48
5.9410-3 54
7.9210-3 59


It is known that the variation of the rate constant k with the absolute temperature T is described by the Arrhenius equation:


k = A exp^[( -Ea )/(RT)]


where Ea is the activation energy, R is the universal gas constant and A is the pre-exponential factor (units of the rate constant). Taking the natural logarithm of both sides affords:


ln k = ln A - Ea/RT


a) For a plot of y = ln k versus x = 1/T, calculate the slope of the best straight line using linear regression.

b) Calculate the activation energy Ea.


2. Relevant equations

Relevant equations listed in part 1

3. The attempt at a solution

Do I need to plot this data? Is there any way to do this without using excel or a graphing calculator? If there isn't, I tried putting these in a spreadsheet, then plot ln k in the y axis and 1/T on the x axis and then use Excel's "trendline" to get the slope. (The slope is Ea/R. So Ea is R x slope for part 2). However, I got -38.619 for the slope.. although, I dont know if this is right or wrong as I seem to keep getting the units wrong, are the not the units for (ln k)/(1/T), which is s^(-1)/degC^(-1), or degC/s??? (where degC = degrees celcius)

If there is another way to figure this out, and if you know why I am getting the wrong units, help would be greatly appreciated! Once I know the first part, part b is a cinch.

Thank-you!
Phys.Org News Partner Science news on Phys.org
Fungus deadly to AIDS patients found to grow on trees
Canola genome sequence reveals evolutionary 'love triangle'
Scientists uncover clues to role of magnetism in iron-based superconductors