What are the solubility rules for ionic compounds

Salts of the alkali metals are soluble. (Note: The alkali metals are in group 1.)

e. g. If M = Li, Na or K, then MX, M2X, M3X, etc. are soluble regardless of what X is.

2. Ammonium ( + NH4

) salts are soluble.

e. g. NH4 X, (NH4

) 2X, (NH4

) 3X, etc. are soluble regardless of what X is.

3. Nitrates NO3

-

are soluble.

e. g. MNO3, M (NO3) 2, M (NO3) 3, etc. are soluble regardless of what M is.

4. Halides i. e. chlorides (Cl-

), bromides (Br-

) and iodides (I-

) are soluble except for the

halides of lead (Pb2+), mercury (Hg+

and 2 + H 2

g) and silver (Ag+

).

e. g. If X = Cl, Br or I, then MX, MX2, MX3, etc. are soluble unless M = Pb, Hg or Ag.

5. Sulfates (2-

SO4

) are soluble except for the sulfates of calcium, strontium, barium, silver

mercury and lead.

e. g. M2SO4, MSO4, M2 (SO4) 3, etc. are soluble unless M is from group 2 (the alkaline

earths) or M = Pb, Hg or Ag.

6. Carbonates (2 - CO3

), phosphates (3 - PO4

) and sulfides (S2-

) are insoluble except for

(i) the carbonates/phosphates/sulfides of the alkalis (because of Rule 1), and

(ii) ammonium carbonate/phosphate/sulfide (because of Rule 2).

7. Hydroxides (OH-

) are insoluble or slightly soluble except for the hydroxides of the

alkalis (because of Rule 1).

Note: The hydroxides of group 2 (the alkaline earth metals) are slightly soluble. Virtually

all other hydroxides are insoluble.