Question

Consider a reaction, $aG+bH\to Products$.

When the concentration of both the reactants G and H is doubled, the rate increases by eight times. However, when concentration of G is doubled keeping the concentration of H fixed, the rate is doubled. The overall order of the reaction is:

• A. $0$
• B. 1
• C. 2
• D. 3

Answer 1

Answer: (D)

3

Given,

$aG+bH\to Products$

Rate constant $k$ = $[G{]}^a\times [H{]}^b$

Over all order of the reaction = a+b

It is given that rate is increased by 8 times when concentration of both reactants is doubled

$\Rightarrow 8\times k=[2G{]}^a\times [2H{]}^b$

$\Rightarrow 8\times k=[2{]}^a\times [G{]}^a\times [2{]}^b\times [H{]}^b$

$\Rightarrow 8\times k=[2{]}^{a+b}\times [G{]}^a\times [H{]}^b$

$\Rightarrow 8\times k=[2{]}^{a+b}\times k$

$\Rightarrow 8=[2{]}^{a+b}$

$\Rightarrow 8=2^3=[2{]}^{a+b}$

$\Rightarrow a+b=3$

$\therefore$ Overall order of the reaction is 3