The reaction A + B → C proceeds at a rate that varies with the initial concentration of the reactants, as follows:
Trial |
[A]t=0 |
[B]t=0 |
Rate t=0 (M/s) |
1 |
0.1 M |
0.5 M |
5 x 10-4 |
2 |
0.2 M |
1.0 M |
1 x 10-3 |
3 |
0.1 M |
4.0 M |
4 x 10-3 |
What is the rate law for the reaction above?
- Rate = k[A]
- Rate = k[B]
- Rate = k[A][B]
- Rate = k[A][B]2
Click for Explanation
To determine the rate law, you must compare trials to see how different initial reactant concentrations affect the initial rate of the reaction. Comparing trial 1 and trial 3, the initial rate in trial 3 increased by a factor of 8. Since [A] is constant and [B] increases by a factor of 8, the reaction rate is first order with respect to B.
Comparing trial 1 and trial 2, the initial rate of trial 2 increase by a factor 2. Since [B] also increases by a factor of 2 and the reaction rate is first order with respect to B, the increase in the reaction rate is due to [B] alone. Thus, the reaction is zero order with respect to A. Thus, the rate law can be described by answer choice B.
Search the Blog
Free Consultation
Interested in our Online MCAT Course or one of our One-on-One MCAT Tutoring packages? Set up a free consultation with one of our experienced Academic Managers!
Schedule NowPopular Posts
-
MCAT Blog How To Prep For The MCAT During COVID-19
-
MCAT Blog How is the MCAT Scored?
-
MCAT Blog Should You Retake the MCAT?

Free MCAT Practice Account
Need great MCAT practice?Get the most representative MCAT practice possible when you sign up for our free MCAT Account, which includes a half-length diagnostic exam and one of our full-length MCAT practice exams.
Learn More
Submit a Comment