Chemistry A-Level
units of k
What units of k means in Chemistry A-Level, as defined for AQA, OCR.
Definitions of units of k
Exam boards and our study guides word this term in slightly different ways. Learn the version your board uses.
Check what you remember
Read the wording for your board, then hide it and explain units of k in your own words. Rough notes are fine. This is a self-check, with no mark or grade.
Reference: AQA
Fixed by the overall order: mol dm⁻³ s⁻¹ for zero order overall, s⁻¹ for first, mol⁻¹ dm³ s⁻¹ for second and mol⁻² dm⁶ s⁻¹ for third.
If t₁/₂ is in seconds, k comes out in s⁻¹; if t₁/₂ is in minutes, convert to seconds first, or report k in min⁻¹ consistently.
Topics that use units of k
- Rate equations (A-level only) (AQA A-Level)
- How fast? (OCR A-Level)
Related terms
- Order of reaction
- Overall order
- Rate equation
- rate of reaction
- Rate-determining step
- zero, first and second order
- Calculating rate and concentration from the rate equation
- Colorimetry
Using units of k in the exam
Check the command word and mark scheme for your exact question. After comparing your explanation with the reference, use the term in an answer on the linked topic. This practice does not predict an exam mark.
Practise Chemistry questions
Create a free account to answer exam-style questions on this topic and get feedback on your answers.
Start free
All Chemistry A-Level termsA week of Premium from your first lesson · Then the free plan continues · No card, no charge