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Imagine that the rate of a chemical reaction only depends on the concentration of a single chemical $A$, with concentration denoted by $[A]$. The reaction is called $m$th order with respect to $[A]$ if it satisfies a rate equation of the following type
$$
-\frac{d[A]}{dt} =k[A]^m
$$
This problem involves trying to find various solutions to rate equations from a purely mathematical perspective. As a rate equation is non-linear in $[A]$ if $m\neq 1$ it is difficult to say how many different sorts of solution it might possess.

To begin with, can $[A] =\lambda+\mu t$ ever be a solution to a rate equation? What would be the order of the reaction? What possible values could $\lambda$ and $\mu$ take?

Can $[A]=(\lambda+\mu t)^n$ ever solve a rate equation when $n$ is a positive whole number other than $1$? A negative whole number? Zero?

What are the possibilities if $n$ is not a whole number?

Which other solutions can you find to a rate equation?


 

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The NRICH Project aims to enrich the mathematical experiences of all learners. To support this aim, members of the NRICH team work in a wide range of capacities, including providing professional development for teachers wishing to embed rich mathematical tasks into everyday classroom practice.

NRICH is part of the family of activities in the Millennium Mathematics Project.

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