High school10 min

Reaction rate: defining it, measuring it, changing it

Calculate an average or instantaneous rate from a curve without losing the sign or the coefficient, choose a monitoring method and name the factors that speed things up.

The essentials

1

The rate of reaction

For a A+b B→c C+d Da\,\mathrm{A} + b\,\mathrm{B} \rightarrow c\,\mathrm{C} + d\,\mathrm{D}: v=−1ad[A]dt=−1bd[B]dt=1cd[C]dt=1dd[D]dtv = -\frac{1}{a}\frac{d[\mathrm{A}]}{dt} = -\frac{1}{b}\frac{d[\mathrm{B}]}{dt} = \frac{1}{c}\frac{d[\mathrm{C}]}{dt} = \frac{1}{d}\frac{d[\mathrm{D}]}{dt} in mol⋅L−1⋅s−1\text{mol}\cdot\text{L}^{-1}\cdot\text{s}^{-1}. The minus sign in front of reactants makes vv always positive; dividing by the coefficient gives the same value whichever species is monitored.
2

Average rate, instantaneous rate

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3

A rate that falls

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4

Monitoring the reaction without disturbing it

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5

Factors affecting the rate

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