Concept preview

What you will be able to do

1. 01Calculate a trial ion product, correcting for dilution
2. 02Compare the trial ion product with Ksp
3. 03Predict whether and roughly how much precipitate forms

When you mix two solutions, will a solid precipitate? To decide, you calculate the trial ion product (often written Q, and sometimes called the trial Ksp). It has exactly the same algebraic form as the Ksp expression, but it is evaluated with the actual ion concentrations present at the moment of mixing, before any reaction. Q is to Ksp precisely what the reaction quotient was to the equilibrium constant in the equilibrium chapter — a snapshot of the system that may or may not be at equilibrium.