Read Titration and Precipitation Problems by Moles First
Both titration-molarity and precipitation-order questions come down to comparing moles carefully — moles of titrant at the endpoint, or moles of Ksp available per anion — before any ranking or calculation.
Chemistry questions first require the material, particles or reaction condition to be identified before a formula or rule is selected.
Molarity from a titration or neutralisation endpoint
When a volume of one reagent exactly neutralises or oxidises a known amount of another (via a titration or an antacid-style neutralisation), set moles of the two reagents equal according to their reaction stoichiometry, then solve for the unknown molarity or volume — don't assume a 1:1 mole ratio unless the balanced equation says so.
Ranking the order of precipitation by Ksp
When a common cation is added dropwise to a solution containing several different anions, the salt with the smallest Ksp (relative to the stoichiometry of its formula) precipitates first — rank by the concentration of cation actually required to reach each salt's Ksp, not by Ksp value alone when the formulas have different ion ratios.
OlympIQ exam lens
- ✓Set up titration/neutralisation problems using the actual mole ratio from the balanced equation, not an assumed 1:1 ratio.
- ✓Order of precipitation from a common-ion addition ranks by the cation concentration needed to reach each salt's Ksp, accounting for stoichiometry.
- ✓A smaller Ksp doesn't automatically mean 'precipitates first' if the salts have different ion ratios — check the actual threshold concentration.
Don't rank precipitation order by raw Ksp value when the salts being compared have different formulas (MX vs MX₂) — convert to the actual cation concentration needed to hit each threshold instead.
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