Questions: Consider the following hypothetical mechanism:
A → B+C k₁
B+D → E k₂
E+D → P+H
If step 1 is the slowest step, then the overall rate law would be:
a. v=k[B][D
b. v=k[P][H]
c. v=k[B][C]
d. v=k[A
Transcript text: Consider the following hypothetical mechanism:
\[
\begin{aligned}
A \rightarrow B+C & k_{1} \\
B+D \rightarrow E & k_{2} \\
E+D \rightarrow P+H &
\end{aligned}
\]
If step 1 is the slowest step, then the overall rate law would be:
a. $v=k[B][D$
b. $\quad v=k[P][H]$
c. $\quad v=k[B][C]$
d. $v=k[A$
Solution
Solution Steps
Step 1: Identify the Rate-Determining Step
In a reaction mechanism, the slowest step is the rate-determining step, which controls the overall reaction rate. According to the problem, the first step \( A \rightarrow B + C \) is the slowest step.
Step 2: Determine the Rate Law for the Rate-Determining Step
The rate law for the rate-determining step is based on the reactants involved in that step. For the step \( A \rightarrow B + C \), the rate law is:
\[
v = k_1[A]
\]
where \( k_1 \) is the rate constant for the first step.
Step 3: Relate the Rate Law to the Overall Reaction
Since the first step is the slowest and rate-determining, the overall rate law for the reaction will be the same as the rate law for this step. Therefore, the overall rate law is:
\[
v = k[A]
\]
where \( k \) is the effective rate constant for the overall reaction.
Final Answer
The correct choice for the overall rate law is:
\[
\boxed{d. \, v = k[A]}
\]