Question

The rate constant is numerically the same for three reactions of first, second and third order respectively. Which of the following is correct?

• A. If $[ A ]=1$ then $r _{1}= r _{2}= r _{3}$
• B. If $[ A ]<1$ then $r _{1}> r _{2}> r _{3}$
• C. If $[ A ]>1$ then $r _{3}> r _{2}> r _{1}$
• D. All of these

Answer 1

Answer: (D)

Consider a reaction; $A \rightarrow$ Product

$\therefore r_{1}=k[A]^{1}$ for I order...(i)

$\therefore r _{2}= k [ A ]^{2}$ for $II$ order...(ii)

$\therefore r _{3}= k [ A ]^{3}$ for III order ...(iii)

$\because k$ is same in all

If $[ A ]=1, r _{1}= r _{2}= r _{3}$

If $[ A ]<1, r _{1}> r _{2}> r _{3}$

If $[ A ]>1, r _{3}> r _{2}> r _{1}$