Topic 18 Acids and bases HL
18.1 Lewis theory of acids and bases 
Understandings:
A Lewis acid is a lone pair acceptor and a Lewis base is a lone pair donor.
When a Lewis base reacts with a Lewis acid a coordinate bond is formed.
A nucleophile is a Lewis base and an electrophile is a Lewis acid.
18.1 Lewis theory vs Bronsted-Lowry theory (HL)
Guidance:
Relations between Brønsted–Lowry and Lewis acids and bases should be discussed. 
This video is a comparison between the Lewis theory and the Bronsted-Lowry theory of acids and bases. 
18.2 Temperature dependence of Kw
Guidance:
This video covers the effect of temperature on the value of the Kw. 
Temperature dependence of Kw worksheet 
18.2 Acid and base dissociation constants (Ka and Kb)
Understandings:
The expression for the dissociation constant of a weak acid (Ka) and a weak base (Kb).
Ka and Kb worksheet
18.2 Calculating the Ka or Kb of a weak acid or base
This video covers how to calculate the Ka or Kb of a weak acid or base.
18.2 Ka, pKa, Kb, pKb, Kw, pKw
Understandings:
For a conjugate acid base pair, Ka × Kb = Kw.
The relationship between Ka and pKa is (pKa = -log Ka), and between Kb and pKb is (pKb = -log Kb).
Applications and skills:
Discussion of the relative strengths of acids and bases using values of Ka, pKa, Kb and pKb.
18.2 Calculating pH of weak acids and bases
Applications and skills:
Calculations involving pH, pOH, Ka and Kb. 
18.3 pH curves 
Understandings:
The characteristics of the pH curves produced by the different combinations of strong and weak acids and bases.
Applications and skills:
The general shapes of graphs of pH against volume for titrations involving strong and weak acids and bases with an explanation of their important features.
18.3 pH curves part 2 
Understandings:
The buffer region on the pH curve represents the region where small additions of acid or base result in little or no change in pH.
Applications and skills:
Only examples involving the transfer of one proton will be assessed. Important features are:
intercept with pH axis
equivalence point
buffer region
points where pKa = pH or pKb = pOH.
18.3 Salt hydrolysis 
Applications and skills:
Prediction of the relative pH of aqueous salt solutions formed by the different combinations of strong and weak acid and base.
18.3 Acid-base indicators 
Understandings:
An acid–base indicator is a weak acid or a weak base where the components of the conjugate acid–base pair have different colours.
Applications and skills:
Selection of an appropriate indicator for a titration, given the equivalence point of the titration and the end point of the indicator.
18.3 Buffer solutions 
Understandings:
The composition and action of a buffer solution.
Applications and skills:
While the nature of the acid–base buffer always remains the same, buffer solutions can be prepared by either mixing a weak acid/base with a solution of a salt containing its conjugate, or by partial neutralization of a weak acid/base with a strong acid/base.


Please note that calculating the pH of a buffer solution will only be assessed in option B (B.7) and option D (D.4).