I am trying to determine the activation energy in the reaction between HCl and Mg, but to do so, I need to find the order of the reaction to get the rate constant (I need the rate constant at different temperatures to find activation energy). After conducting the experiment, I determined that the order of HCl was 1.87, but how would I find the order of magnesium? Magnesium is a pure solid, so it's not like I can change its concentration. Should I just leave it out of the rate law expression?
I also have another question: Can orders be non-integer number values? I have my order of HCl listed as 1.87, but should I just round it to 2?
Help would be much appreciated, thanks.