Topic 18.1: Calculations involving acids and bases

18.1.1 State the expression for the ionic product constant of water (Kw).

18.1.2 Deduce [H+(aq)] and [OH-(aq)] for water at different temperatures given Kw values

Since we know that

As the temperature increases, the equilibrium has shifted to the right. When it is shifted to the right this means the concentration of Hydrogen ions has increased thus lowering the pH. Thus the solution has a lower pH at higher temperature.


18.1.3 Solve problems involving [H+(aq)], [OH-(aq)], pH and pOH

18.1.4 State the equation for the reaction of any weak acid or weak base with water, and hence deduce the expressions of Ka and Kb

18.1.5 Solve problems involving solutions of weak acids and bases using the expression:

Ka x Kb = Kw
pKa + pKb = pKw
pH + pOH = pKw

18.1.6 Identify the relative strengths of acids and bases using values of Ka, Kb, pKa and pKb