Playbook
Ionic Equilibria
122 q - 2.96/paper - 2% HARD. Log arithmetic — pH, α, buffers, Ksp — with two recall pages to take first.
- Questions in the bank
- 122
- q/paper (2024–25 papers)
- 2.96
- Tagged HARD
- 2%
- Subtopics
- 6
Strand: Calculate
When you’ll see it
A pH, a Ka or Kb, a degree of dissociation, a buffer, a salt in water, or a solubility and its Ksp.
How this chapter is tested
122 q at 2.96 a paper, 2% HARD. Two pages are recall and belong on the first sweep: Theories of Acids and Bases (12 q) and Salt Hydrolysis (16 q) — which salt gives an acidic or basic solution comes from whether its parent acid and base are strong or weak.
The rest is log arithmetic: pH = −log[H⁺] and pH + pOH = 14; α = √(K/c) for a weak electrolyte (Ostwald); pH = pKa + log([salt]/[acid]) for a buffer; and Ksp from solubility by salt type — the largest page at 29 questions.
The sub-skills
The distinct skills inside the chapter, in the order to learn them.
pH and pOH
pH = −log[H⁺]; at 25 °C, pH + pOH = 14. For a strong acid, [H⁺] = concentration × basicity.
Weak electrolytes
α = √(K/c), [H⁺] = √(Ka·c).
Buffers
pH = pKa + log([salt]/[acid]); pOH = pKb + log([salt]/[base]).
Solubility product
AB: Ksp = s². AB₂: 4s³. A₂B₃: 108s⁵. A common ion lowers solubility.
Traps to expect
Distractor shapes this chapter reuses. The Traps page covers the patterns that cut across chapters.
Ksp by the wrong salt type
For CaF₂, Ksp = s·(2s)² = 4s³, not s². Each salt type has its own power.
The basicity of the acid
0.01 M H₂SO₄ gives [H⁺] = 0.02 M, so pH = 1.7, not 2.
Learn it before you drill it
This chapter has full teaching notes — foundations, worked examples, self-checks and a per-subtopic mastery checkpoint. Read the notes once, then drill subtopic by subtopic below.
Ionic Equilibria notesDrill every ionic equilibria question
122 questions from the bank, scoped to 6 bundled subtopics.
Drill one subtopic at a time
The 6 subtopics this playbook covers, in catalog order.
Related playbooks
Often paired with this one — the technique, the trap or the taxonomy overlaps. Drill these next.