Question

For a reaction $A \xrightarrow{K_1} B \xrightarrow{K_2} C$ If the rate of formation of B is set to be zero then the concentration of B is given by:

• A. $K_1K_2[A]$
• B. $(K_1 - K_2)[A]$
• C. $(K_1 + K_2)[A]$
• D. $(K_1/K_2)[A]$

Answer 1

The Correct Option is D

The rate of formation of B is:
\[ \frac{d[\text{B}]}{dt} = k_1[\text{A}] - k_2[\text{B}]. \]
For the rate of formation of B to be zero:
\[ \frac{d[\text{B}]}{dt} = 0. \]
Substitute:
\[ k_1[\text{A}] - k_2[\text{B}] = 0. \]
Rearrange to find [B]:
\[ k_1[\text{A}] = k_2[\text{B}] \implies [\text{B}] = \frac{k_1}{k_2}[\text{A}]. \]
Thus, the concentration of B is:
\[ [\text{B}] = \left(\frac{k_1}{k_2}\right)[\text{A}]. \]