Question

Which of the following will react fastest (produce more product in a given time) and which will react at the highest rate?
(a) $1$ mole of $A$ and $1$ mole of $B$ in $1$ litre vessel.
(b) $2$ mole of $A$ and $2$ mole of $B$ in $2$ litre vessel.
(c) $0.2$ mole of $A$ and $0.2$ mole of $B$ in $0.1$ litre vessel.

Answer 1

Suppose a reaction,

$aA+bB\to$products

Rate$=K{\left[A\right]}^a{\left[B\right]}^b$ where $K$ is a constant

For $\left(a\right)$, Rate$=K\left[A\right]\left[B\right]=K\times 1\times 1=K$

For $\left(b\right)$, Rate$=K\times 2\times 2=4K$

For $\left(c\right)$, Rate $=K\times 0.2\times 0.2=0.04K$

Rate for $\left(b\right)$ is highest.

(i) (b) will react fastest because of more reactant present, there will be more product produced per unit time, (ii) (c) will react at highest rate because $\left[A\right]$ and $\left[B\right]$ are highest and thus rate will be more.

$\therefore$ Answer is $\left(b\right)$