[pretzalisa]

Hi... I'm really confused about the difference between Ksp (concentration solubilty constant) and K'sp (thermodynamic solubility constant)
I realise that Ksp = [X][Y].YxYy, and that K'sp = YxYy but the equations don't really explain much for me
For instance, why does K'sp --> Ksp when ax --> [X]
I can't find any in deph explination of the difference anywhere in my book or online, so the more descriptive you are the better

Thanks so much for taking your time to help me

[Borek]

It won't hurt to start with correct equations. K'sp is NOT γ_xγ_y and Ksp is not γ_x[X]γ_y[Y].

If anything

Ksp = [X][Y]

K'sp = a_xa_y = γ_x[X]γ_y[Y]

and

K'sp = γ_xγ_yKsp

[pretzalisa]

Well yes that is why i'm getting abit confused, it seems it would be that way... but my text book "Fundamentals in Analytical Chemistry" By Skoog et al. shows it as the opposite way
I did make an error with K'sp though

Its definatley listed in the book as:
Ksp = ax.ay = K'sp.YxYy

So does this mean K'sp = [X][Y], whereas Ksp take activity into account?

Thanks for your help

[Borek]

The way you listed them Ksp is the CONCENTRATION solubility product, so it is [X][Y]. K'sp is THERMODYNAMIC - so it involves activities, and activty is concentration times activity coefficient. Perhaps you used wrong symbols, perhaps they are mixed in the book - no idea.

[pretzalisa]

the book must be wrong? that's the only way it will make sense hehe hmmm i'll talk to my lecturer 2moro.


Thanks for your replies

[koolbird]

hey,
I also recently came up with the term thermodynamic solubility product(Kt). can anyone xplain me more about it or please give me place where i can find some info about it. I googled but nothing found.
thankzz

[Borek]

http://www.chembuddy.com/?left=pH-calculation&right=ionic-strength-activity-coefficients

[koolbird]

thankzzzzzzzz

[koolbird]

hey,
i need to know if it's possible to use thermodynamic solubility product(Kt) for solubility predictions such as we use Ksp in predicting of occurring precipitates.
If can, how can we do it....

[Borek]

Using thermodynamic solubility product gives correct results, contrary to concentration sp. You need to know ionic strength of the solution. Calculation procedure is outlined on the page you have already read - it is identical for any ionic equilibrium, no matter if it is acid/case equilibrium, or solubility, or complexation reaction.

[koolbird]

thank you very much for replying.
it was really helpful.....thankzzzz again.