PLEASE. SOMEONE HELP ME WITH CHEMISTRY! DUE TOMORROW..?

[celeste]

I'm having trouble with this question that I've been working on for a while now with my program online, since I don't have a teacher its difficult. If anyone could even assist me on some of the questions that'd be greatly appreciated. :(

Question: Use the concentration and rate data presented in the table below to answer the following questions about the hypothetical reaction:

Line --- [A] (mol/L) --- [B] (mol/L) --- [C] (mol/L) --- Rate (mol/L.s)
1 --- 0.100 --- 0.100 --- 0.100 --- 3.6 x 10-2
2 --- 0.200 --- 0.100 --- 0.100 --- 3.6 x 10-2
3 --- 0.100 --- 0.200 --- 0.100 --- 7.2 x 10-2
4 --- 0.200 --- 0.200 --- 0.200 --- 2.9 x 10-1
5 --- 0.300 --- 0.200 --- 0.300 --- ?

a) Why would you expect this reaction to be a multi-step reaction, based on the overall reaction? (1 mark)

b) What is the order of the reaction, with respect to each reactant? (3 marks)

c) What is the overall order of the reaction? (1 mark)

d) Write the rate law. (1 mark)

e) How does the data confirm that this is a multi-step reaction? (1 mark)

f) Predict the rate indicated by the "?" (2 marks)

g) Propose a reaction mechanism with the third step as the rate-determining step. (4 marks)

With any questions please help!

[chozai65]

a) It's pretty rare to have three molecules A, B,and C come together at once.

b) Comparing lines 1 and 2: you doubled A and the rate is the same. So A is zero order.
Comparing lines 1 and 3, you doubled B and the rate is doubled. So B is first order.
Comparing lines 1 and 4, you doubled everything and the rate octupled (i.e. x8). We know doubling A has no effect, and doubling B would double the rate. This leaves a factor of 4 unaccounted for, which we conclude is the effect of doubling C. Since doubling C gives 4x the rate, C is second order.

c) The overall order of the reaction is 0+1+2 = 3.

d) The rate law is rate = k[B][C]^2.

e) The rate law doesn't depend on A. This means A is not part of the rate-determining step of the reaction. So it must be involved in another step of the reaction. Therefore, there are at least 2 steps in this reaction.

f) Tripling A should have no effect according to the rate law. Doubling B would by itself double the rate, and tripling C would by itself multiply the rate by 9. The combined effect is to multiply the rate by 18 (= 2 x 9). The expected rate is 18 x 3.6x10^-2 = 6.5x10^-1.

g) This is the hardest part, definitely.
step 1: A + A <==> D
step 2: C + C <==> E
step 3: B + E ---> F
step 4: F + D <==> G the product
Note: other mechanisms are possible. I don't really like the idea of A reacting with itself to form D, but if I didn't include it, there is no step 1 and then the second step is rate-determining.