Question

For a chemical reaction $A\to B$. it is found that the rate of reaction doubles when the concentration A is increased four times. What is the order in A for this reaction?

• A. Two
• B. One
• C. Half
• D. Zero

Answer 1

Answer: (C)

Half

For the give reaction; $A\to C$
$Rate=r=k[A{]}^n....(i)$; where $n=$ order of reaction.
Also given that, rate doubles when concentration of $A$ becomes $4$ times
Therefore new rate $=2r=k[4A{]}^n....(ii)$
On dividing (i) by (ii) we get:
$\frac{r}{2r}=\frac{k[A{]}^n}{k[4A{]}^n}$
$\therefore \frac{1}{2}={\left[\frac{1}{4}\right]}^n$
$\therefore {\left[\frac{1}{2}\right]}^1={\left[\frac{1}{2}\right]}^{2n}$
$2n=1$ and $n=\frac{1}{2}$.