ATAR Notes: Forum

HSC Stuff => HSC Science Stuff => HSC Subjects + Help => HSC Chemistry => Topic started by: priyanka.jatan on January 02, 2020, 06:30:21 pm

Title: Solubility in terms of Ksp
Post by: priyanka.jatan on January 02, 2020, 06:30:21 pm
Hello! How do you determine what chemicals are more soluble with reference to their Ksp?
For instance, if substance a has a Ksp of 5.02 x 10-6 and substance b has a Ksp of 1.43 x 10-20, which substance is the most soluble? Is the rule the lesser the Ksp, the greater the solubility or vice versa?
Title: Re: Solubility in terms of Ksp
Post by: Sine on January 02, 2020, 07:24:45 pm
Quote from: priyanka.jatan on January 02, 2020, 06:30:21 pm
Hello! How do you determine what chemicals are more soluble with reference to their Ksp?
For instance, if substance a has a Ksp of 5.02 x 10-6 and substance b has a Ksp of 1.43 x 10-20, which substance is the most soluble? Is the rule the lesser the Ksp, the greater the solubility or vice versa?
The greater the solubility product constant means that the compound is more soluble.

\(\ce{BaSO4(s) <=> Ba^2+(aq)+ + SO4^2-(aq)}\)

Ksp = [Ba2+][SO42-]

Logically speaking if you look at the above solubility product and the associated chemical reaction you can see that the higher Ksp means that there is a greater concentration of the soluble ions.
Title: Re: Solubility in terms of Ksp
Post by: louisaaa01 on January 02, 2020, 11:09:15 pm
Quote from: priyanka.jatan on January 02, 2020, 06:30:21 pm
Hello! How do you determine what chemicals are more soluble with reference to their Ksp?
For instance, if substance a has a Ksp of 5.02 x 10-6 and substance b has a Ksp of 1.43 x 10-20, which substance is the most soluble? Is the rule the lesser the Ksp, the greater the solubility or vice versa?

Hi Priyanka,

It’s also worth noting that Ksp can only be used to directly compare solubility when the ionic compounds dissociate to form the same number of ions. For instance, you can compare the solubility of BaSO4 and PbSO4 using their Ksp values (higher Ksp = more soluble) but you couldn’t, say, directly compare the solubility of BaSO4 and PbCl2 using Ksp. For the latter, you’d need to use your ICE tables and/or other quantitative techniques.