How to Find out the Overall Order of a Reaction – Part 2

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.

However, there exists a shortcut if the given data is relatively simple! In some cases, a few mathematical tweaks may solve the problem without a calculator or a log table.

Question:

In a reaction between A & B, the initial rate of reaction (r0) was measured for different initial concentrations of A & B as given below:

A/ mol L–1

0.20

0.20

0.40

B/ mol L–1

0.30

0.10

0.05

r0/mol L–1 s–1

5.07 × 10–5

5.07 × 10–5

1.43 × 10–4

What’s the overall order of the reaction?

Solution:



Click/tap to enlarge the image

k = Rate constant, x = Order w.r.t. A

Optimistic math on the 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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