How to Find out the Overall Order of a Reaction – Part 4

The order of reaction is a number which quantifies the degree to which the rate of a chemical reaction depends on concentrations of the reactants.


In other words, the order of reaction is the exponent to which the concentration of a particular reactant is raised. One could write the rate equations for the given sets of data and solve for the orders w.r.t. the reactants.

Question:

The reaction between Nitric oxide and Bromine is represented below. The proposed reaction mechanism is as follows:

NO + Br2 ⇌ NOBr2 (fast)

NOBr2 + NO → 2NOBr (slow)

What is the overall order of the reaction consistent with the proposed mechanism?

Solution:



Click/tap to enlarge the image

k = Rate constant, K = Equilibrium constant

It is difficult to determine the rate law from a reaction mechanism in which an intermediate (NOBr2, in this case) is involved in the slow (rate determining) step.

Ordeal with orders❓ Let Chemaficionado know in the comments below or at mychemistryhomework@gmail.com❗

References:

(1)    Wikipedia Contributors. Rate equation. Wikipedia. https://en.wikipedia.org/wiki/Rate_equation.

(2)    Brown, C.; Ford, M. Higher Level Chemistry, 2nd ed.; Pearson Education: Harlow, Essex, 2014.

(3)    Ncert. Chemistry : Textbook for Class XII - Part.I; National Council Of Educational Research And Training: New Delhi.

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