Ever wondered how on earth you would remember your solubility rules for the HSC? Look no further then NAGSAG.
Here is a more comprehensive list of your solubility rules! Remember, the NAGSAG acronym is sufficient for your HSC chemistry exams. The list below is something you build an intuition for, rather then going in a rote memorizing.
- Salts containing Group I elements (Li+, Na+, K+, Cs+, Rb+) are almost always soluble.
- Salts containing the ammonium ion (NH4+) are also soluble.
- Salts containing nitrate ion (NO3–) are generally soluble.
- Salts containing Cl –, Br –, or I – are usually soluble. Exceptions to this rule are halide salts of Ag+, Pb2+, and (Hg2)2+.
- Most silver salts are insoluble. AgNO3 and Ag(C2H3O2) are common soluble salts of silver; virtually all others are insoluble.
- Most sulfate salts are soluble. Important exceptions to this rule include CaSO4, BaSO4, PbSO4, Ag2SO4 and SrSO4 .
- Hydroxide salts of Group I elements are soluble.
- Hydroxide salts of Group II elements (Ca, Sr, and Ba) are slightly soluble.
- Hydroxide salts of transition metals and Al3+ are insoluble.
- Most sulfides of transition metals are highly insoluble, including CdS, FeS, ZnS, and Ag2S. Arsenic, antimony, bismuth, and lead sulfides are also insoluble.
- Group II carbonates (CaCO3, SrCO3, and BaCO3) are insoluble, as are FeCO3 and PbCO3.
- Chromates are frequently insoluble.
- Phosphates such as Ca3(PO4)2 and Ag3PO4 are frequently insoluble.
- Fluorides such as BaF2, MgF2, and PbF2 are frequently insoluble.
Note answers are at the bottom.
You are unsure whether you have a solution of barium nitrate or lead nitrate in an unlabelled flask, outline reactions you would perform to determine which of the two salt solutions you have present. [2 marks]
Which of these substances is likely to form a precipitate?
a) CaSO4 b) NaCl c) AgBr
Explain why some salts are soluble in water whilst other salts are insoluble.
Predict whether a precipitate will form as a result of this reaction:
The products of the reaction must be examined; if either of the substances formed in the reaction is insoluble, a precipitate will form.
Considering NaNO3, Rule #3 states that nitrates tend to be soluble. A precipitate of this compound will not form.
Next, consider Ag2S. According to Rule #5, that sulfides tend to be insoluble. Therefore, because of this compound, a precipitate will form in the course of this reaction.
B, use NAGSAG mnemonic – looking at which is insoluble in water
D, use NAGSAG mnemonic – looking at which is soluble in water