Asked by Jessica Tessier on Jul 31, 2024
Verified
Consider the three-step mechanism for the reaction of A through intermediates B and C to produce D shown below.
A → B Ea = 15 kcal/mol, ΔH° = 13 kcal/mol
B → C Ea = 10 kcal/mol, ΔH° = -6 kcal/mol
C → D Ea = 2 kcal/mol, ΔH° = -20 kcal/mol
Which of the three steps is rate-limiting?
A) The reaction of A to B.
B) The reaction of B to C.
C) The reaction of C to D.
D) All three steps occur at the same rate; there is no rate-limiting step.
E) The most exothermic step is rate-limiting.
Rate-Limiting
Describes the slowest step in a chemical reaction pathway or process, which determines the overall reaction rate.
Exothermic
A chemical reaction that releases energy by light or heat.
- Analyze energy diagrams of reactions to ascertain the mechanisms and energy aspects involved.
Verified Answer
ZK
Zybrea KnightAug 02, 2024
Final Answer :
A
Explanation :
The rate-limiting step in a reaction mechanism is the step with the highest activation energy (Ea), which determines the overall reaction rate. In this case, the reaction of A to B has the highest activation energy of 15 kcal/mol, making it the rate-limiting step.
Learning Objectives
- Analyze energy diagrams of reactions to ascertain the mechanisms and energy aspects involved.