This topic deals with acid-base equilibria in aqueous solution. Hence the Brønsted-Lowry definitions of acid/base are primarily used in the understanding of pH of solutions. (See Section 4)

Content

● Acid dissociation constants, Ka and the use of pKa

● Base dissociation constants, Kb and the use of pKb

● The ionic product of water, Kw

● pH: choice of pH indicators

● Buffer solutions

This course is suitable for GCSEALevel students sitting for the 9729 H2 Chemistry Course. This course is also offered as an Early Bird Bonus for Term 3 Payments.

A strong acid is one that undergoes complete dissociation in aqueous solution.

Examples: HCl(aq) + H2O(l) ->H3O+(aq) + Cl−(aq)

HNO3(aq) + H2O(l) -> H3O+(aq) + NO3−(aq)

A weak acid is one that undergoes partial dissociation in aqueous solution.

Examples: CH3COOH(aq) + H2O(l) H3O+(aq) + CH3COO−(aq)




Candidates should be able to:

(a) show understanding of, and apply the Bronsted-Lowry theory of acids and bases, including the concept of conjugate acids and conjugate bases

(b) explain qualitatively the differences in behaviour between strong and weak acids and bases in terms of the extent of dissociation

(c) explain the terms pH; Ka; pKa; Kb; pKb; Kw and apply them in calculations, including the relationship Kw = Ka x Kb

(d) calculate [H+(aq)] and pH values for strong acids, weak monobasic (monoprotic) acids, strong bases, and weak monoacidic bases

(e) explain the choice of suitable indicators for acid-base titrations, given appropriate data

(f) describe the changes in pH during acid-base titrations and explain these changes in terms of the strengths of the acids and bases

(g) (i) explain how buffer solutions control pH

(ii) describe and explain their uses, including the role of H2CO3/HCO3- in controlling pH in blood

(h) calculate the pH of buffer solutions, given appropriate data