Home › MCQs › EEJ MAIN Chemistry › Question #7117
Back to Questions
EEJ MAIN Chemistry QUESTION #7117
Question 1
For an elementary chemical reaction $A_{2} \xrightleftharpoons[k_{-1}]{k_{1}} 2A$, which of the following is the correct mathematical expression for the rate of change of concentration of $A$ ($\frac{d[A]}{dt}$)?
  • $k_{1}[A_{2}] - k_{-1}[A]^{2}$
  • $2k_{1}[A_{2}] - k_{-1}[A]^{2}$
  • $k_{1}[A_{2}] + k_{-1}[A]^{2}$
  • $2k_{1}[A_{2}] - 2k_{-1}[A]^{2}$✔️
Correct Answer Explanation
The rate of appearance of $A$ from the forward reaction is $2 \times (\text{rate of forward reaction}) = 2k_1[A_2]$. The rate of disappearance of $A$ in the backward reaction is $2 \times (\text{rate of backward reaction}) = 2k_{-1}[A]^2$. Thus, the net rate is $\frac{d[A]}{dt} = 2k_{1}[A_{2}] - 2k_{-1}[A]^{2}$.