[bssjonny]

I've found using the internet that for the reaction of iodine and propanone with HCl catalyst that the reaction is 0 order wrt iodine.
This also seems to be the case when i look at the progress curves i have drawn for the reaction where you can see that iodine concentration tends to decrease in a linear fashion
My question is: Should this really be the case?
Since the order wrt propanone and HCl is both 1 for each i would expect that as they get used up in the reaction the rate would change and so the line shouldnt be straight.

Any thoughts?