Practice question · Numerical answer
A first-order reaction has a half-life of 25 s. What percentage of the original reactant remains after 75 s?
Hints
- Work out how many half-lives fit into the elapsed time.
- 75 s is three half-lives, and each one halves what is left.
Show the answer
12.5 (answers within ±0.6 count)
Why
75 s is half-lives, so the fraction remaining is %. Note the reactant is never entirely consumed in a first-order process.
Practise Reaction Kinetics
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