Okay, so Jordan and Jon tell me that K and Ksp are different. How so? I found their explanation to be somewhat lacking 
Thx
Thx
K vs. Ksp
- Thread starter tncekm
- Start date
- Joined
- Feb 18, 2008
- Messages
- 16,027
- Reaction score
- 2
They really aren't different. If you calculate the K for an aqueous dissociation reaction, you get Ksp...The only difference lies in that K can be used for any reaction. When it's specific to solubility, it's called Ksp. When its an acid (proton dissociation), it's Ka. When it's a base (proton acceptor), it's Kb.Okay, so Jordan and Jon tell me that K and Ksp are different. How so? I found their explanation to be somewhat lacking
Thx
I've been listening to audio osmosis...and while it's great while you're driving, it's not the best substitute to reading.
Right, that's what I thought.
However, here is what confused me in the book, verbatim:
"Solubility and the solubility product are not the same thing. Solubility product or Ksp is a constant found in a book. Solubility is the maximum number of moles of the solute that can dissolve in the solution."
See, I thought Ksp was a number I could look up in a book that described solubility for an aqueous solution--which, to me, means they're not different.
However, here is what confused me in the book, verbatim:
"Solubility and the solubility product are not the same thing. Solubility product or Ksp is a constant found in a book. Solubility is the maximum number of moles of the solute that can dissolve in the solution."
See, I thought Ksp was a number I could look up in a book that described solubility for an aqueous solution--which, to me, means they're not different.
- Joined
- Feb 18, 2008
- Messages
- 16,027
- Reaction score
- 2
Yeah, Ksp can be looked up. I think that they don't mean solubility constant (K) when they refer to solubility. I think they're just talking about how soluble a substance is...as in what's the point of saturation for a give substane (ie 5 moles dissolves in 1 L). And the solubility is different than the solubility const. You have the right idea behind it, so just stick to your instincts.
- Joined
- Feb 18, 2008
- Messages
- 16,027
- Reaction score
- 2
I think it's their wording that's a little confusing.
I hope I'm understanding it right, though....I may be wrong.
- Joined
- Oct 31, 2003
- Messages
- 161
- Reaction score
- 2
When solubility of a product is mentioned or asked for, think in terms of molar solubility like jgberken said instead of just Ksp because even if Ksp of a substance is smaller than another substance it could be more soluble if its Molar solubility is higher.
For example: you are given Ksp and Molar solubility for two substances CaCO3 and CaF2
Ksp CaCO3 = 8.7 x 10^-9 M^2
Ksp CaF2 = 4 x 10^-11 M^3
Based on the above information alone you would think CaCO3 is more soluble.
Now calculate the molar solubility (M):
M CaCO3 = sq root of (8.7 x 10^-9 M^2) = > 9.0 x 10^-5 M
M CaF2 = cube root of (4/4 x 10^-11 M^3) = > 2.0 x 10^-4 M
From the above calculations you can tell than CaF2 is more soluble than CaCO3.
It is important that you calculate the molar solubility of a given compound from its Ksp value to determine its actual solubility and that's what EK probably means when it says that solubility constant and solubility are not the same thing. They are talking about Ksp and M and not Ksp and K or at least that's what I think
For example: you are given Ksp and Molar solubility for two substances CaCO3 and CaF2
Ksp CaCO3 = 8.7 x 10^-9 M^2
Ksp CaF2 = 4 x 10^-11 M^3
Based on the above information alone you would think CaCO3 is more soluble.
Now calculate the molar solubility (M):
M CaCO3 = sq root of (8.7 x 10^-9 M^2) = > 9.0 x 10^-5 M
M CaF2 = cube root of (4/4 x 10^-11 M^3) = > 2.0 x 10^-4 M
From the above calculations you can tell than CaF2 is more soluble than CaCO3.
It is important that you calculate the molar solubility of a given compound from its Ksp value to determine its actual solubility and that's what EK probably means when it says that solubility constant and solubility are not the same thing. They are talking about Ksp and M and not Ksp and K or at least that's what I think
- Joined
- Feb 13, 2004
- Messages
- 860
- Reaction score
- 61
agree with above... in brief,
K = the constant for a reaction, ie "products over reactants"
Ksp = the solubility product constant, a special type of "K"
solubility = the moles of something you can dissolve in a given amount of solute, usually expressed as some permutation of mol/L.
i think your initial confusion was from mixing up "K" with "solubiliy."
K = the constant for a reaction, ie "products over reactants"
Ksp = the solubility product constant, a special type of "K"
solubility = the moles of something you can dissolve in a given amount of solute, usually expressed as some permutation of mol/L.
i think your initial confusion was from mixing up "K" with "solubiliy."
