Question

For a reaction, $A+3B\to P$, rate $=\frac{-d\left[A\right]}{dt}=k\left[A{]}^2\right[B]$, the expression for the rate of reaction in terms of change in the concentration of $B$, $\frac{-d\left[B\right]}{dt}$ will be:

• A. $k{\left[A\right]}^2\left[B\right]$
• B. $k\left[A\right]{\left[B\right]}^3$
• C. $3k{\left[A\right]}^2\left[B\right]$
• D. $\frac{1}{3}k{\left[A\right]}^2\left[B\right]$

Answer 1

The correct option is C $3k{\left[A\right]}^2\left[B\right]$

$-\frac{1}{3}\frac{d\left[B\right]}{dt}=\frac{-d\left[A\right]}{dt}-\frac{d\left[B\right]}{dt}=3\left(\frac{-d\left[A\right]}{dt}\right)-\frac{d\left[B\right]}{dt}=3k\left[A{]}^2\right[B]$