Ksp issues...

[zzto]

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So lets say you have a solubility problem with a salt AB3 and you have to make the Ksp expression to solve it. I get really confused as to whether the Ksp would be (x)(3x)^3 OR if it becomes (x)(x)^3 . This is the one thing in gen chem that I get wrong again and again and would love to know what simple fact I'm missing!

 

[zzto]

Gracias!

 

[ZPederson11]

watch chad's video. He explains this topic very well.

 

[matty675]

It would be [A][B^3]. If you then do your ICE table, you'll see that it translates to (x)(3x^3)

 

[vk223]

So lets say you have a solubility problem with a salt AB3 and you have to make the Ksp expression to solve it. I get really confused as to whether the Ksp would be (x)(3x)^3 OR if it becomes (x)(x)^3 . This is the one thing in gen chem that I get wrong again and again and would love to know what simple fact I'm missing!

It's (x)(3x)^3. Imagine you are doing the ICE table. Since you AB3 dissociates into A+3B, you will have x for Aand +3xfor B. The +/- x in the Change always correlates to coefficient.
For these types of problem, I like to write the Ksp expression first. So Ksp=A*B^3
and fill the "x" into the Ksp expression. Since A= x and B = 3x, the Ksp would be (x)(3x)^3

 

[disciple155]

Like the upper comments state, Ksp use (x)(3x)^3. However, it is (x)(x)^3 if you're doing a precipitation problem where you compare Qsp to Ksp.

 

[zzto]

Thanks for all the great and super fast responses everybody that helps a lot!