Question about Ksp

[drlovett]

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Hey everybody,

I recently came across this question, and for some reason, I am having a hard time with it. Maybe I am just thinking way too much...

If the Ksp of CaCO3(s) is 10–10, what is the concentration of Ca2+ ions in a saturated solution consisting of 30 grams of CaCO3 in 100 mL of H2O?

TPR says [Ca2+] = 10-5 M. I guess I am wondering why they didn't take into account the initial concentration of CaCO3. If anything, I would think it would be 3 x 10-5 M, as 3 mol of Ca2+ is produced for every 3 mol of CaCO3 used.

Appreciate any feedback!

 

[sazerac]

"in a SATURATED solution". Once you reach Ksp, no more chalk will dissolve. That's the point of Ksp.

 

[drlovett]

Ugh, you're right.... seemed to gloss over that fact. Thank you!