I am currently doing a chemistry EEI that involves determining the orders of reaction for a particular reaction. The reaction chosen for the experiment is:
Mg + 2HCl
The EEI asks students to hypothesis what the orders of reaction might be based on secondary data. I was able to locate some secondary data, which is shown below:
Concentration of HCl 0.8 1.5 2.0 3.0
Time take (s) 36 18 11 8
By graphing the data I was able to determine that the overall order of reaction followed a roughly that of a second order. When it came to hypothesise what the individual orders of reaction were (for Mg and HCl) I thought that it could be achieved by finding two concentrations that were double. Because there was a concentration of 1.5 M and 3 M i thought this could be used to see if the order of reaction was first, second etc...
Because there is roughly half the time taken between the two concentrations I assumed that it was a first order with respect to HCl and therefore a first order with respect to Mg.
To verify this however, I thought that I would do a quick trial experiment to ensure that my predictions were indeed correct. This is where I ran into problems. Upon trying each of the test, I encountered the following results:
Concentration: 1 0.5
Time taken: 174 723
According to my data, there is roughly a 4x increase in time taken for a concentration increase of 2x. This would indicate a second order, which would go against my original prediction.
What I would like to know is, would anyone be able to confirm what the orders of reaction are with respect to each of the reactants?
Thanks a lot for your help,