If Ksp of Mg(OH)2 is more than that of MgCO3 which gets precipitated first?

NCERT XI Chemistry

It is because of high solubility product of Mg(OH)2 as compared to that of MgCO3, that Mg(OH)2 is precipated.

Is this statement from my textbook correct?
How a more soluble compound gets precipated easily than a less soluble compound?

1 Answer
anor277
Mar 24, 2018

Ksp is an equilibrium quantity....and I think your text book has a typo....

Explanation:

The section of the text tries to explain that BICARBONATES, i.e. salts of HCO−3 are generally soluble, yet carbonates, salts of CO2−3 are generally insoluble. This is often observed for insoluble sulfates versus soluble bisulfates, salts of HSO−4.

To look at the data, (and as physical scientists we MUST look at data...)...this site quotes Ksp=5.61×10−12 for Mg(OH)2.....solubilities in the range of a few ppm...

and this site quotes Ksp=10−7 for MgCO3, i.e. 0.139⋅g⋅L−1, or 139⋅ppm..

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