Chemistry / Unit 10 Chem 1919 short lesson, about 20 seconds
Precipitation Prediction via Q vs. Ksp
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The idea
Mixing two solutions forms a precipitate if the resulting ion concentrations give Q greater than Ksp, the same Q-vs-K logic built earlier.
In practice
Mixing solutions giving Q = 5 × 10⁻⁸ for a salt with Ksp = 1.8 × 10⁻¹⁰ predicts a precipitate, since Q exceeds Ksp.
Where people slip
Forgetting that mixing dilutes each ion's concentration before computing Q gives a wrong precipitation call.
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