To predict which ionic compounds are insoluble in water you use “solubility rules” to first eliminate the soluble possibilities.
You go down the solubility rules in order and stop at the first rule that applies.
SOLUBILITY RULES
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All common of ##”NH”_4^+## and the Group 1 are soluble.
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##”NO”_3^”-“, “ClO”_3^”-“, “ClO”_4^”-“, “C”_2″H”_3″O”_2^”-“## — all common nitrates, chlorates, perchlorates, and acetates are soluble.
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##”F”^”-“, “Cl”^”-“, “Br”^”-“, “I”^”-“## — all halides are soluble EXCEPT those of ##”Ag”^+, “Hg”_2^”2+”, “Pb”^”2+”## and the fluorides of ##”Mg”^”2+”, “Ca”^”2+”, “Sr”^”2+”##, and## “Ba”^”2+”##.
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##”SO”_4^”2-“## — most sulfates are soluble EXCEPT those of ##”Sr”^”2+”, “Ba”^”2+”, “Ca”^”2+”, “Pb”^”2+”##, ##”Hg”_2^”2+”##, and ##”Hg”^”2+”##.
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##”CO”_3^”2-“, “C”_2″O”_4^”2-“, “OH”^”-“, “O”^”2-“, “SO”_3^”2-“, “PO”_4^”3-“, “CrO”_4^”2-“, “S”^”2-“## — all carbonates, oxalates, hydroxides, oxides, phosphates, chromates, and sulfides are insoluble.
EXAMPLES
Classify these compounds as soluble or insoluble in water:
tin(II) sulfate — soluble (Rule 4)
lead(II) chromate — insoluble (Rule 5)
ammonium sulfide — soluble (Rule 1)
strontium chlorate — soluble (Rule 2)
silver bromide — insoluble (Rule 3)
sodium phosphate — soluble (Rule 1)
copper(I) carbonate — insoluble (Rule 5)
barium sulfate — insoluble (Rule 4)
