1. The problem statement, all variables and given/known data Ok, so basically, our teacher gave us some solubility rules... then we did a problem where we mixed two solutions and checked to see if a precipitate would form. So he calculated Qsp for one of the products and compared it to Ksp for that product, he did not calculate Qsp and Ksp and forth 'other'... this 'other' product obeyed the solubility rules. So from what I understand, when you mix two solutions to see if a precipitate forms, you ignore the soluble products because they have infinite solubility? I mean, do the solubility rules tell us that those substances have infinite solubility?