For my Chemistry IA, I want to compare the activation energy of the decomposition of hydrogen peroxide catalayzed by potassium iodide (KI) versus the activation energy of the decomposition of hydrogen peroxide catalyzed by a solution of catalase enzyme, to determine which one is the more efficient catalyst (i.e. the one that yields a lower activation energy for the reaction). For both catalyzed reactions, I'm going to measure the volume of oxygen gas evolved per second using a gas syringe, at 5 different temperatures (30°C, 35°C, 40°C, 45°C and 50°C). Then, I'm going to create an Arrhenius plot for each catalyzed reaction, and determine the activation energy from the plot.
There are a few things that I'm confused about:
1. How do I determine the appropriate concentrations and volumes for each chemical?
2. How do I calculate the rate constant based on the data I collect? (In order to create the Arrhenius plot, I would need to plot ln(rate constant) on the y-axis and 1/Temperature on the x-axis).
Alternatively, I found an article that says that I can simply plot ln(initial rate) over 1/Temperature. (https://eic.rsc.org/feature/investigating-activation-energies/2020172.article) This article says the following:
The variation of reaction rate with temperature is given by the Arrhenius equation, which in its integrated form is:
k = Ae-Ea /RT
where A is a constant, the frequency factor, Ea is the activation energy, R is the universal gas constant (8.314 J mol-1K-1), and T is the absolute temperature. Since initial rate = ck, the initial rate can be found by:
initial rate = cAe-Ea /RT
ln (initial rate) = lncA - Ea/RT
log (initial rate) = logcA - Ea/2.303RT
Thus, we can plot log (initial rate) against 1/T to obtain a straight line. The slope is multiplied by -2.303R to get Ea. The rates can be expressed in volume of oxygen per second or in arbitrary units because the slope of the straight line will not be affected.
Would this work as well? I figure it would be easier to plot ln(initial rate), because then I wouldn't need to calculate the values for the rate constant at each temperature.