Question

The rate constant is numerically the same for three reactions for first, second and third order respectively. Which one is true at the moment for rate of all three reactions if concentration of reaction is same and bigger then 1 M.

• A. $r_1=r_2=r_3$
• B. $r_1>r_2>r_3$
• C. $r_1<r_2<r_3$
• D. All

Answer 1

The correct option is C $r_1<r_2<r_3$

According to kinetic theory ,

Rate of first order reaction , r₁ = K₁[A]¹

Rate of 2nd order reaction , r₂ = K₂[A]²

Rate of 3rd order reaction , r₃ = K₃[A]³

A/C to question,

K₁ = K₂ = K₃ = K [ numerically, rate constant are same ]

And [A] > 1 M

So, [A]³ > [A]² > [A]

So, r₃ > r₂ > r₁