Question

For the reaction $2A+B\to C+D,-\frac{d\left[A\right]}{dt}=k\left[A{]}^2\right[B]$. The expression for $\frac{-d\left[B\right]}{dt}$ will be:

• A. $K\left[A{]}^2\right[B]$
• B. $1/2K\left[A{]}^2\right[B]$
• C. $K\left[A{]}^2\right[2B]$
• D. $K\left[2A{]}^2\right[B]$

Answer 1

Answer: (B)

$1/2K\left[A{]}^2\right[B]$

According to rate law,

$-\frac{1}{2}\times \frac{dA}{dt}=-\frac{dB}{dt}$

We have, $\frac{-d\left[A\right]}{dt}=k\left[A{]}^2\right[B]$

$\therefore -\frac{dB}{dt}=\frac{1}{2}k\left[A{]}^2\right[B]$