Question

Determine the order of reaction

2 N2O5 --> (g)4 NO2 (g) + O2 (g)

using the following information:

t (min) 0 1 2 3... infinity
[O2] (mol/L) 0 0.148 0.252 0.326... 0.500

Answer 1

It is of Zero Order reaction with respect change in the concentration of Oxygen, as the units provides (moles/lit) are for zero order reaction.

But overall order of reaction is First order with respect to formation of Nitrogen dioxide.

Decomposition of N₂O₅:

2N₂O₅(g) → 4NO₂(g) + O₂(g)

From the equation it is clear that 2 moles of Nitrogen pentoxide (N₂O₅) decomposes to produce 4 moles of Nitrogen dioxide (NO₂) and 1 mole of Oxygen (O₂).

From the given:

After 1 min of time the reaction produces 0.148 m of Oxygen, thus it also produces (4*0.148) m of NO₂ from (2*0.148) m of N₂O₅.

Deterimination of rate constant (k):

Let the initial concentration of N₂O₅ (a) = 1

After t = 1 min the concentration of N₂O₅ will be (a-x) = [1 - (2*0.148)]

k = (2.303/t)*log a/(a-x)

= (2.303/1)*log(a/[1 - (2*0.148)])