For example: CdS, FeS, and ZnS are all insoluble.Only sulfide compounds made with these elements are soluble in water. As with many of the other rules, there are exceptions including barium, calcium, magnesium, sodium, potassium, and ammonium. Recognize that most sulfides are insoluble in water.For example: Na 2SO 4 is completely soluble, but CaSO 4 and BaSO 4 are not soluble.Sulfate salts containing these ions are insoluble. Exceptions to this rule include the following ions Ca +2, Ba +2, Pb +2, Ag +, Sr +2, and Hg +2. Most of the salt compounds containing SO 4 are soluble in water. Understand that most sulfate salts are soluble.For example: Compounds like CaCO 3, PbCrO 4, and Ag 3PO 4 are all insoluble while compounds like Na 3PO 4 and (NH 4) 2CO 3 are soluble.
Exceptions to this rule include the Group 1A metals and NH 4 + compounds which are soluble. The chemical formulas for each of these are as follows: CO 3 (carbonates), CrO 4 (chromates), and PO 4 (phosphates).
Note that PbCl 2, PbBr 2, and PbI 2 are soluble in HOT water.For example: AgCl and Hg 2Cl 2 are both insoluble.Compounds consisting of these nonmetals and ions are not soluble. Exceptions to this rule include silver, lead, and mercury. Group 17 nonmetals include chlorine (Cl -), bromine (Br -), and iodine (I -). Recognize that salts containing Group 17 nonmetals are generally soluble.For example: Fe(OH) 3, Al(OH) 3, and Co(OH) 2 are insoluble, but LiOH and NaOH are soluble.The exception to this rule is that hydroxide salts formed with Group 1 elements are soluble because Group 1A elements are always soluble. Some hydroxide salts are slightly soluble: hydroxides formed with Group 2 elements (Ca, Sr, and Ba). Know that most hydroxide compounds are insoluble.For example: NH 4OH is soluble even though it contains a hydroxide.The ammonium ion, NH 4 +, makes salt compounds that completely dissociate in the presence of water. Understand that all ammonium salts are soluble.For example: KNO 3, NaClO 3, and CH 3COONa are all soluble.
When a nitrate, NO 3 -, chlorate, ClO 3 -, or acetate, CH 3COO -, form a salt, they are soluble in water. Know that salts containing nitrates, chlorates, and acetates are soluble.For example: KCl and LiOH are soluble in water.They are the alkali metals and include Li, Na, K, Cs, and Rb. The first column of the table contains the Group 1A elements. The periodic table is organized into rows and columns called periods and groups, respectively. Recognize that salts containing Group 1A elements are soluble.