# How can I determine the activation energy of a reaction if the reaction rate constant is unknown?

I am trying to conduct an experiment to determine the activation energy of the following chemical reaction:

1. $$\ce{IO3- (aq) + 3HSO3- (aq) -> I- (aq) + 3SO4^2- (aq) + 3H+ (aq)}$$
2. $$\ce{5I- (aq) + 6H+ (aq) + IO3- (aq) -> 3I2 (aq) + 3H2O (l)}$$

The Arrhenius Equation can be rewritten as $$\ln k = \frac{-Ea}{{\rm R}T} + \ln A$$ Therefore, if ln k and 1/T were plotted on a graph, the slope of the line should be equal to -Ea/R.

I can use temperature as my independent variable and the reaction time as my dependent variable. However, I am unsure as to how to determine the reaction rate constant (k) of the reaction experimentally from the reaction time.

• You have two reactions there. One will be rate limiting (I don't know which), so your plots will give you the activation energy for that part only. As for how, this is standard rate law problems, although this one is a smidge messier than normal. You might have to assume steady state Iodide and Hydrogen Cation – Lighthart Mar 3 '16 at 19:27