Calculations involving Acids and Bases
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Understandings● The expression for the dissociation constant of a weak acid (Ka) and a weak base (Kb).
● For a conjugate acid–base pair, Ka Å~ Kb = Kw. Guidance ● The value Kw depends on the temperature. ● Only examples involving the transfer of one proton will be assessed. ● Calculations of pH at temperatures other than 298 K can be assessed. ● The relationship between Ka and pKa is pKa = –logKa and between Kb and pKb is pKb = –logKb. |
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Applications and skills● Solution of problems involving [H+(aq)], [OH–(aq)], pH, pOH, Ka, pKa, Kb, and pKb.
Guidance ● Students should state when approximations are used in equilibrium calculations. ● The use of quadratic equations will not be assessed. ● Discussion of the relative strengths of acids and bases using values of Ka, pKa, Kb, and pKb. Guidance The calculation of pH in buffer solutions will only be assessed in options B.7 and D.4. |
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Inquiry questions
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Calculations involving Acids and Bases
Test yourself
1. Question: Determine the pH for each of the given solutions.
a. 0.150 M HNO3
b. 0.150 M CH3COOH, Ka = 1.8 × 10-5
c. 0.150 M CHOOH, Ka = 3.5 × 10-4
a. 0.150 M HNO3
b. 0.150 M CH3COOH, Ka = 1.8 × 10-5
c. 0.150 M CHOOH, Ka = 3.5 × 10-4
acid deposition
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