[xangelofxdeathx]

Which substance is the least soluble in H₂O?

A) K₂CO₃
B) KHCO₃
C) Ca(HCO₃)₂
D) CaCO₃

Right now, I am missing some kind of key fact about the solubility of a substance in water.
This is what I know right now:

1) Like dissolves Like, so polar substances will dissolve in water very well since water is polar. On the other hand non-polar substances won't be very soluble in water.

2) Ionic compounds tend to dissolve in polar liquids, thus they are soluble in water.

Can someone show me how I would do this problem? And also can someone briefly summarize the rules/theories I should know in order to do future problems similar to this one?

Thanks. (The answer is D by the way)

[Vixklen]

Dont we use Ksp to solve these?? 

peace
vixklen

[AWK]

THere are simple qualitative rules concerning solubilities of inorganic salts
http://members.tripod.com/~EppE/soluble.htm
http://www.shs.nebo.edu/Faculty/Haderlie/apchem/SolubilityRules.pdf
http://www.ausetute.com.au/solrules.html

[english]

Unfortunately quantitative determination of solubility of such substances is no easy task.  You're best bet is to go with AWK's links.

Learn your solubility rules!  Tattoo them on your arm.  o__O