Ksp Precipitation Wording

[tbogdan89]

---

Members don't see this ad.

In this problem, I interpreted the question to ask, "when will anions and cations appear?" to which I wrote out for example, AgCl <--> Ag+ and Cl-. I wanted a shift RIGHT because I wanted to increase the cation and anions, so I said if K > Q = Shift Right.

Apparently the wording of precipitation had me thrown off and I should have been looking to shift left? Although the answer is saying precipitation occurs when K < Q which I agree, in my opinion it would be the solid that precipitates, not the anions and cations.

By that notion, should the word "preciptate" automatically mean that we want to shift left?

 

[FeralisExtremum]

I wouldn't think of it in terms of shifting left or right, that will be entirely dependent on how a specific reaction is written out. The key is "will precipitate", as in, will form a precipitate. Regardless of how your equation is set up, that will always be when Qsp > Ksp. The question didn't ask when cations and anions will dissolve from a solid in solution. It's a really important distinction to understand the verb 'precipitate' in chemistry means to form a solid precipitate, not the other way around.

 

[Anthony Bogdan]

Perfect answer, thank you