When to use this calculator
Estimate reactant concentration after a first-order reaction interval. Assumes a first-order rate law with a constant rate coefficient.
Explore the reaction quantities & yield calculators for other questions in this topic. For a related calculation, use the Percent Purity Calculator: Calculate a sample’s pure-component mass as a percentage of total sample mass.
PUTTING IT INTO PRACTICE
First Order Reaction Remaining: a worked example
The values below are an illustrative example, not a recommendation. Replace them with measurements or assumptions that match your question.
| Input | Example value |
|---|---|
| Initial concentration | 1 |
| First-order rate constant (1/s) | 0 |
| Elapsed time (s) | 10 |
| Result | 1 input concentration units |
- Check the input labels and enter the example values above.
- Apply the relationship: Remaining concentration = initial × exp(−rate constant × time).
- The result is 1 input concentration units, rounded for display.
How to interpret your result
Assumes a first-order rate law with a constant rate coefficient.
Balance the chemical equation before using mole ratios. Identify the limiting reactant separately. Yield, purity and atom economy measure different aspects of a reaction and should not be substituted for one another.
Frequently asked questions
Is percent yield the same as atom economy?
No. Yield compares actual product against a theoretical amount; atom economy describes stoichiometric use of reactant mass in the desired product.
When is the first order reaction remaining calculator useful?
Estimate reactant concentration after a first-order reaction interval. Assumes a first-order rate law with a constant rate coefficient.
How do I use the first order reaction remaining calculator?
Enter initial concentration, first-order rate constant (1/s), elapsed time (s). The result updates automatically. Use the units shown beside each input; the example values illustrate the method.
Which formula does this calculator use?
Remaining concentration = initial × exp(−rate constant × time).
What should I check before using the result?
Assumes a first-order rate law with a constant rate coefficient.
How are results rounded?
Scalar numbers display up to six decimal places, with scientific notation for very large or small values. Text, fraction, date and schedule outputs use the format described on the tool. Intermediate calculations use JavaScript floating-point arithmetic. Keep sensible precision for your measurements.
Further reading
For background on this topic, see OpenStax: quantitative chemical analysis ↗. This is a topic reference, not an external review or endorsement of this tool.
Calculators Map editorial process · Updated · Methods and limitations