Question

The solution to question 101 of chapter 12 of Zumdahl Zumdahl chemistry 9th edition is only partially answered. It does not calculate the activation energy.Here is the question. Experiments have shown that the average frequency of chirping by a snowy tree cricket (Oecanthus fultone) depends on temperature as shown in the table. Chirping rate: 178, 126, 100 Temperature (C) 25.0,20,3, 17.3 What is the apparent activation energy of the process that controls the chirping? What is the rate of chirping expected at a temperature of 7.5C

Answer 1

Arhenius equation can be used to determine the apparent activation energy of chirping rate.

Arhenius equation is lnK= lnKo-Ea/RT

K= rate constant ( chirping rate in this case), Ko= Frequency factor. Ea= activation energy, T= temperature in K.

R= activation energy= 8.314 J/mole.K

So the plot of ln K vs 1/T has to be generated to obtain the best fit. The slope gives -Ea/R from which Ea can be calculated.

      

the equation of best fit from the plot is lnK= -6395*1/T + 26.64, slope is -Ea/R= -6395 and Ea= 6395*8.314 J/mole =53168 J/mole

at 7.5 deg.c= 7.5+273K= 280.5K

lnK= -6395*1/280.5 +26.64= 3.84

K (chirping rate at 7.5 deg.c) = 46.59