Question

For a reaction, $\frac{1}{2}A⟶2B$, the rate of disappearance of $A$ is related to the rate of appearance of $B$ by the expression______________.

• A. $\frac{-d\left[A\right]}{dt}=4\frac{d\left[B\right]}{dt}$
• B. $\frac{-d\left[A\right]}{dt}=\frac{1}{2}\frac{d\left[B\right]}{dt}$
• C. $\frac{-d\left[A\right]}{dt}=\frac{1}{4}\frac{d\left[B\right]}{dt}$
• D. $\frac{-d\left[A\right]}{dt}=+\frac{d\left[B\right]}{dt}$

Answer 1

Answer: (C)

$\frac{-d\left[A\right]}{dt}=\frac{1}{4}\frac{d\left[B\right]}{dt}$

$-2\frac{d\left[A\right]}{dt}=\frac{1}{2}\frac{d\left[B\right]}{dt}-\frac{d\left[A\right]}{dt}=\frac{1}{4}\frac{d\left[B\right]}{dt}$