Constant half-life
What Constant half-life means in Chemistry A-Level, as defined for AQA, OCR.
Definitions of Constant half-life
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Reference: OCR
The time for the concentration of the reactant to fall from any value to half that value stays the same as the reaction proceeds, and does not depend on concentration.
The time for the concentration to halve is the same at every starting concentration, which is the defining feature of a first order reaction.
A constant half life on a concentration against time curve signals first order.
Topics that use Constant half-life
- Determination of rate equation (A-level only) (AQA A-Level)
- How fast? (OCR A-Level)
Related terms
- continuous monitoring
- Rate-determining step
- Calculating rate and concentration from the rate equation
- Colorimetry
- Concentration–time graphs
- Controlled comparison of experiments
- Deducing order from initial-rate data
- Deducing order with respect to a reactant
Using Constant half-life in the exam
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