Video Transcript
The table below shows the
solubility product of four substances and the product of ion concentrations for an
aqueous solution of each substance. In which solution can more of the
substance be dissolved?
When discussing a substance’s
ability to be dissolved, also called its solubility, we can use a solubility
product. In this question, we are trying to
determine which of the four solutions in the table can dissolve more of the solid
substance it contains. In other words, we would like to
identify which solution is not yet saturated with dissolved ions. Let’s look more closely at this
idea using a generic substance whose formula we can write as MA.
The solid MA will dissolve to form
its constituent ions in solution, which are M1+ and A1−. The lowercase 𝑚 and 𝑎 represent
the stoichiometric coefficients of the ions. The information provided in the
table includes the solubility product values of each substance. The solubility product can be
abbreviated as K sp. The K sp of a substance can be
expressed as the product of its ion concentrations in a saturated solution raised to
the power of their stoichiometric coefficients.
The relationship between the
solubility product of a substance and the current product of the ion concentrations
tells us about the state of saturation. When the K sp value and the product
of the ion concentrations are equal, this means the solution is saturated. This means that for that particular
substance, the solution currently contains the maximum amount of dissolved ions in
that volume of water. When the current product of the ion
concentrations is greater than the K sp value for that particular substance, a
precipitate forms, since there are more ions present than are able to dissolve. When the K sp value is greater than
the current product of ion concentrations, this means more ions of that particular
substance can be dissolved. So, the solution is not yet
saturated.
Let’s use the table to find which
solution can dissolve more substance. We are looking for the solution
whose substance has a higher K sp value than the product of the ion
concentrations. We can see that the only solution
whose solubility product is greater than the product of its ion concentrations is
solution C. Therefore, the solution in which
more of the substance can be dissolved is solution C.
