Work through the list without notes. If you cannot do a statement, follow its link, then come back. Guide = study guide; Practice = practice questions.
Understanding
- I can explain why [H₃O⁺] in a weak acid solution is much smaller than the starting acid concentration. (Guide: “Weak means mostly not ionized”; Practice Q1)
- I can rank [HA], [H₃O⁺], [A⁻] and [OH⁻] in a weak acid solution. (Guide: Figure 1; Practice Q1)
- I can write K_a and K_b expressions, leaving water out, and say that a larger pK means a weaker acid or base. (Guide; Revision notes)
- I can explain why K_a does not change on dilution but percent ionization rises. (Guide: “Percent ionization”; Practice Q4)
Calculation
- I can find the pH of a weak acid from c and K_a or pK_a, and check the 5% approximation. (Guide: Worked example 1; Practice Q2)
- I can solve the quadratic when the 5% check fails. (Practice Q6)
- I can find the pH of a weak base, going through [OH⁻] and pOH. (Guide: Worked example 3; Practice Q5)
- I can calculate K_a or K_b and percent ionization from a measured pH. (Guide: Worked example 2; Practice Q5)
- I can convert between K_a and K_b, or pK_a and pK_b, for a conjugate pair. (Guide: “Linking a conjugate pair”; Practice Q3)
Reasoning
- I can compare two weak acids at the same concentration and say which has the higher pH and which has the stronger conjugate base. (Practice Q7)
- I can explain why the weaker acid leaves more un-ionized molecules in solution. (Practice Q7(c))
- I can explain why a weak and a strong acid at the same concentration have different pH values. (Guide: Figure 1 caption; Practice Q2)
All ticked? Move on to Topic 8.4, Acid-Base Reactions and Buffers, or return to the course roadmap.