can someone explain this please..

[prsndwg]

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Hi,

So i was reading through Kaplan bb and I got to the end of Solutions chapter on Gchem and its talking about Ksp and all those good stuff.
On the side notes, DAT Synopsis, here is what they say and I dont get it..

" Every slightly soluable salt of general formula MX3 will have Ksp= 27x^4, where X is the molar solubility."

there is also the same phrases about MX2 and Ksp=4X^3 & Mx where Ksp=X^2.

I am confused on this. Can somebody explain this please.

Thanks

 

[iwannabadentist]

consider this salt:
XaYb --> aX + bY, where a and b represent the respective molecules of X and Y.
the Ksp for this salt would be:
Ksp = (X^a)*(Y^b)

now consider:
MX2 --> M + 2X
this means that upon dissociation, for every 1 M, there are 2 X. So now you can substitute X with the quantity (2M). Then you would have:
MX2 --> M + 2 (2M)
now to get the Ksp, you simply raise each molecule to the power of its coefficient:
(M)^1 * (2M)^2 = M*4(M^2) = 4(M^3)

you use the same concept for salts with different ratios. hope that clears things up

 

[prsndwg]

consider this salt:
XaYb --> aX + bY, where a and b represent the respective molecules of X and Y.
the Ksp for this salt would be:
Ksp = (X^a)*(Y^b)

now consider:
MX2 --> M + 2X
this means that upon dissociation, for every 1 M, there are 2 X. So now you can substitute X with the quantity (2M). Then you would have:
MX2 --> M + 2 (2M)
now to get the Ksp, you simply raise each molecule to the power of its coefficient:
(M)^1 * (2M)^2 = M*4(M^2) = 4(M^3)

you use the same concept for salts with different ratios. hope that clears things up

How did you get MX2 --> M + 2X? please explain it to me.

 

[bbwreckerz04]

How did you get MX2 --> M + 2X? please explain it to me.

When it dissociates you get one mole of M and 2 of X