What Is the Correct Rate Law for These Reaction Mechanisms?

[toothpaste]

1. For the reaction

2NO + Cl2 --> 2NOCl

Match the appropriate rate law to each postulated mechanism.
A Rate = k[NO]2[Cl2]2
B Rate = k[NO][Cl2]
C Rate = k[NO][Cl2]2
D Rate = k[Cl2]
E Rate = k[Cl2]2
F Rate = k[NO]
G Rate = k[NO]2[Cl2]
H Rate = k[NO]2
I None of the above

NO + Cl2 --> NOCl2 slow
NOCl2 + NO ---> 2NOCl fast

2NO --> N2O2 slow
N2O2 + Cl2 --> 2NOCl fast

NO + Cl2 NOCl2 ---> fast equilibrium
2NOCl2 NOCl3 + NOCl ---> slow
NOCl3 ---> NOCl + Cl2 fast

NO + Cl2 ---> NOCl2 fast equilibrium
NOCl2 + NO ---> 2NOCl slow

i have no idea where to start. book isn't very helpful. basically, you look at the slow reaction then you subisitute the intermediate for the fast reaction. But i don't know what i do next. Do i cancel or what?

2. 5Br-(aq) + BrO3-(aq) + 6H+(aq) 3Br2(l) + 3H2O(l)

The above reaction is expected to obey the mechanism:

BrO3-(aq) + H+(aq) <-->HBrO3(aq) Fast equilibrium
HBrO3(aq) + H+(aq) <---> H2BrO3+(aq) Fast equilibrium
H2BrO3+(aq) + Br-(aq) <---> (Br-BrO2)(aq) + H2O(l) Slow
(Br-BrO2)(aq) + 4H+(aq) + 4Br-(aq) <---> products Fast


For each of the given rate expressions choose the correct expression for the rate constant (k)

-d[BrO3-]/dt
-d[Br-]/dt
-d[H+]/dt

 

[Nino MMP]

-d[HBrO3]/dt -d[H2BrO3+]/dt -d[Br-BrO2]/dt A k = [BrO3-][H+] B k = [Br-][H+] C k = [H+]2 D k = [HBrO3] E k = [H2BrO3+] F k = [Br-BrO2] G None of the above Answer: A k = [BrO3-][H+]

 

[Blueshift5]

my response to this content would be to first acknowledge the complexity of the question and the difficulty in understanding reaction mechanisms. I would then suggest breaking down the problem into smaller parts and focusing on each individual reaction in the mechanism.

For the first question, I would advise the person to start by identifying the slow reaction in the mechanism, which is the rate-determining step. In this case, it is the first reaction in the mechanism. Then, they can substitute the intermediate (NOCl2) for the fast reaction and use the rate law for the overall reaction (2NO + Cl2 --> 2NOCl) to match with one of the given rate laws. In this case, it would be Rate = k[NO][Cl2]2.

For the second question, I would suggest looking at each individual reaction in the mechanism and determining which reactant or product is changing over time. This would help identify the correct rate expressions for each reactant or product, which would then correspond to the correct expression for the rate constant (k). In this case, the correct expressions would be k1 for -d[BrO3-]/dt, k3 for -d[Br-]/dt, and k2 for -d[H+]/dt.

Overall, understanding reaction mechanisms takes practice and patience. I would encourage the person to continue studying and seeking help when needed. It is also important to consult reliable resources and seek guidance from a knowledgeable mentor or teacher.