Trial experiments for determining order

[Jolene Robles 2H]

When determining the order with respect to reactants in an experiment (for example when there is a table with trial 1,2,3 and initial A and initial B and initial rate) how do you know which two trials to divide by in order to determine the order?

[Valeria Perez 3J]

In order to determine the order of a species you want to use two equations that have the other concentrations remain constant. You want to be able to observe the effect on the rate when only 1 of your species is changing in concentration at a time, so you would select the ones that have consistent concentrations in all but one reactant. Hope that helps!

[Stephanie_manasyan]

Typically you want to choose the trials that you see lead to a change in concentration/ rate when increasing another variable. This way, you can determine its order. If you only have 3 experiments, compare 1 and 2 and 1 and 3. Hope this helps!

[Melody L Lehman 2C]

If you want to find the affect of changing the concentration of A on the rate of the reaction you would choose two trials where the concentration of the reactants other than A do not change. For example, you would choose trial 1 with [A] = 1.00 [B] = 1.00 [C] = 1.00 and trial 2 with [A] = 2.00 [B] = 1.00 [C] = 1.00
Only the concentration of A changed, so you know if the rate doubles, the order of A is first order.