The reaction 2NO(g) + 2H2(g) N2(g) + 2H2O(g) goes twice as fast when the concentration of H2 is doubled but four times as fast when the concentration of NO is doubled. What is the overall reaction order?
I did it like this:
k[NO]^m[H2]^n
2r=[H2]^n, meaning that the order for H2 is 1
4r=[NO]^m, meaning that the order for NO is 2
I got overall reaction order to be 3
Did I do this correct, or do I need to use reaction mechanism and ICE tables?
Thanks again!
You are absolutely right. Good work.
Yes, you have correctly determined the overall reaction order for the given reaction.
To determine the overall reaction order, you can use the rate expression you provided:
rate = k[NO]^m[H2]^n
From the information given, you found that doubling the concentration of H2 (which is equivalent to raising [H2] by a power of 2) results in the rate increasing by a factor of 2. This suggests that the reaction is first order with respect to [H2], so n = 1.
Similarly, doubling the concentration of NO (which is equivalent to raising [NO] by a power of 2) results in the rate increasing by a factor of 4. This suggests that the reaction is second order with respect to [NO], so m = 2.
Now, looking at the overall reaction order, you sum up the values of m and n to obtain 2 + 1 = 3. Therefore, the overall reaction order is 3.
You do not need to use a reaction mechanism or ICE tables in this case since you were given the information about how the concentration changes affect the rate of the reaction directly.