Question

Order of a reaction is an experimental quantity.

(1) Calculate the overall order of a reaction which has the rate expression :

(a) Rate = k[A]^1/2 [B]^3/2

(b) Rate = k[A]^3/2 [B]^-1

(2) The initial concentration of N₂O₅ in the following first order reaction N₂O₆(g) → 2NO₂(g) + 1/2 O₂(g) was 1.24 × 10^-2 mol/L at 318 K.

The concentration of N₂O₅, after 60 min was 0.20 × 10^-2  mol/L. Calculate the rate constant of the reaction at 318 K.

Answer 1

(1). (a) Order = \(\frac{1}{2}+\frac{3}{2}\) = 2

 (b) Order = \(\frac{3}{2}+(-1)\) = \(\frac{1}{2}\)

(2). For a 1^st order reaction,

k = \(\frac{2.303}{t}log\frac{[R]_0}{[R]}\)

= \(\frac{2.303}{60}log\frac{1.24\,\times\,10^{-2}}{0.20\,\times\,10^{-2}}\)

= \(\frac{2.303}{60}log\,6.2\,min^{-1}\)

k = 0.0304 min^-1