Chemistry A-Level
approximations
What approximations means in Chemistry A-Level, as defined for AQA.
Definition of approximations
Check what you remember
Read the wording for your board, then hide it and explain approximations in your own words. Rough notes are fine. This is a self-check, with no mark or grade.
Reference: AQA
The assumptions that the H⁺ from water is negligible, so [H⁺] = [A⁻], and that so little acid dissociates that [HA] at equilibrium equals the concentration made up.
Topics that use approximations
- Weak acids and bases, Ka, for weak acids (A-level only) (AQA A-Level)
Related terms
- comparing rates
- position of equilibrium
- strength versus concentration
- acid dissociation constant
- partial dissociation
- pKa
- ranking acid strength
Using approximations 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.
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