State whether the following compounds are soluble or insoluble:

Question

an explanation would be great as well:)

Answer 1

The way you can tell if an ionic compound is soluble or insoluble is knowing the "Solubility Rules". You should have them in your textbook or maybe a PowerPoint or handout from your teacher. They are usually in a chart form, most often the first half of the chart talks about Soluble stuff... It will say "all compounds with NO₃^- in them are soluble" (or something like that). Then there is usually a column in the table that lists exceptions to the rule, if there are any.

In the case of compounds containing the nitrate anion (NO₃^-) there are no exceptions. Therefore, if you see any compound with this ion in it, you can assume that it will be soluble, no matter what the cation - Li⁺, K⁺, Pb⁺², Fe⁺³, Cr⁺³, Ba⁺², Ag⁺, Ca⁺², etc. any cation, it doesn't matter, these will be soluble if combined with the nitrate anion!

However, the solubility rules also say that "all chlorides, bromides, and iodides are soluble, except..." Which means if you have a compound containing Cl-, Br-, or I-, you should assume that it is soluble. unless it is one of the exceptions! The exceptions listed for these are Pb⁺², Ag⁺, and Hg₂⁺² (diatomic mercury cation). This means NaCl would be soluble (because it's not an exception to the solubility rule) but PbCl₂ would be insoluble (because it is an exception to the solubility rule).

The rules also have a general list of things that are usually Insoluble. These basically work the opposite - if you see those ions in a compound you should assume that it is NOT soluble (Insoluble means not soluble). Unless it is an exception! Or something already discussed in the Solubility rules that doesn't have an exception... For example, they would usually say something about sulfates generally being insoluble, so if your compound contains SO₄^-2 ion, you should assume it is not soluble. However, an exception to this rule is Mg²⁺ ion combined with it, so MgSO₄ would be soluble! Also, in your solubility rules, in the Soluble part, it probably said "All compounds containing Na⁺, Li⁺, K⁺ or NH₄⁺ are soluble", so if you have any of these cations combined with sulfate, then it is still going to be soluble, because these guys are exceptions to all of the Insoluble compound rules.

Sometimes your teacher will let you have a copy of the Solubility Rules when you take your test, so you don't necessarily have to memorize them. But you definitely need to know how to use the chart/list!

Answer 2

a & d are soluble: all nitrates are soluble and all chlorides except those of Ag⁺, Pb²⁺, and Hg₂²⁺ are soluble.

b & c are insoluble: all iodides, except those of Ag⁺. Pb²⁺, and Hg₂²⁺ are soluble (see comment for chlorides, above) and most sulfates are insoluble including those of Ag⁺ (which, by the way, shows an incorrect formula for silver sulfate. It should be Ag₂SO₄).