In a certain mystery liquid, the compounds #Al_2S_3#, #K_3N#, #Na_2S#, and #RbBr# each have a value of #Ksp = 1.0 xx 10^-10#. Which of these solids should be the least soluble in the mystery liquid? (Choices in answer).
The answer is indeed A. rubidium bromide
The options are:
E. All four solids should be equally soluble in
the liquid since their
The idea behind this problem is very simple - you have to use the definition of the solubility product constant,
An ionic compound's solubility is measured by its degree of dissociation. That means that a more soluble ionic compound will produce greater concentrations of cations and anions in solution.
Take a look at the dissociation equilibria for your compounds
Even without doing any calculations, you can predict that
You can determine the molar solubility of each of those compounds by replacing the concentrations of the cations and anions with
This will get you
Now it becomes obvious that rubidium bromide will have the lowest molar solubility, i.e. the smallest
This means that one mole of