Acids, equilibrium & kinetics · SL/HL
Reaction rate
Find average change per time or inverse time.
Your values
Number formats & units
Use decimal dots in datasets. Single values also accept decimal commas and scientific notation such as 1.2e-3 or 1.2 × 10⁻³.
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Result & working
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Interpretation & assumptions
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Formula & example
The relationship
What the variables mean
| Symbol | Meaning |
|---|---|
| Stoichiometric coefficient when normalizing to a reaction rate. |
Worked example
- Method
- Change divided by time
- Initial value
- 0.100
- Final value
- 0.060
- Time interval / s
- 40.0
- Stoichiometric coefficient ν
- 1
- Result unit (optional)
- mol dm⁻³ s⁻¹
0.001 mol dm⁻³ s⁻¹
Follow the example steps
- |Δquantity| = |0.06 − (0.1)| = 0.04
- Species average rate = |Δquantity|/Δt = 0.001
- Reaction rate = species rate/ν = 0.001 / 1 = 0.001
Common mistakes
An average over an interval is not an instantaneous rate.
Incorrect approach
Δc = −0.2 mol dm⁻³ over 10 s: instantaneous rate = −0.02
Correct approach
Average concentration change per second = −0.2/10 = −0.02 mol dm⁻³ s⁻¹
More checks before you submit
- Do not call an average over a long interval an instantaneous rate.
Method notes
A tangent gives an instantaneous rate on a smooth graph; this calculator gives a secant/average rate between two values. In clock experiments, 1/t is a proxy only when the same observable threshold is used.