Solubility Rules Mnemonic – NAG SAG

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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.

1. Salts containing Group I elements (Li⁺, Na⁺, K⁺, Cs⁺, Rb⁺) are almost always soluble.
2. Salts containing the ammonium ion (NH₄⁺) are also soluble.
3. Salts containing nitrate ion (NO₃^–) are generally soluble.
4. Salts containing Cl ^–, Br ^–, or I ^– are usually soluble. Exceptions to this rule are halide salts of Ag⁺, Pb²⁺, and (Hg₂)²⁺.
5. Most silver salts are insoluble. AgNO₃ and Ag(C₂H₃O₂) are common soluble salts of silver; virtually all others are insoluble.
6. Most sulfate salts are soluble. Important exceptions to this rule include CaSO₄, BaSO₄, PbSO₄, Ag₂SO₄ and SrSO₄ .
7. Hydroxide salts of Group I elements are soluble.
8. Hydroxide salts of Group II elements (Ca, Sr, and Ba) are slightly soluble.
9. Hydroxide salts of transition metals and Al³⁺ are insoluble.
10. Most sulfides of transition metals are highly insoluble, including CdS, FeS, ZnS, and Ag₂S. Arsenic, antimony, bismuth, and lead sulfides are also insoluble.
11. Group II carbonates (CaCO₃, SrCO₃, and BaCO_​3) are insoluble, as are FeCO₃ and PbCO₃.
12. Chromates are frequently insoluble.
13. Phosphates such as Ca₃(PO₄)₂ and Ag₃PO₄ are frequently insoluble.
14. Fluorides such as BaF₂, MgF₂, and PbF₂ are frequently insoluble.

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Note answers are at the bottom.

Question 1.

Question 2.

Question 3.

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]

Question 4.

Which of these substances is likely to form a precipitate?

a) CaSO₄ b) NaCl c) AgBr

Question 5.

Explain why some salts are soluble in water whilst other salts are insoluble.

Question 6.

Predict whether a precipitate will form as a result of this reaction:

2AgNO3+Na2S→Ag2S+2NaNO3(1)(1)2AgNO3+Na2S→Ag2S+2NaNO3

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.

Answers.

Question 1.

B, use NAGSAG mnemonic – looking at which is insoluble in water

Question 2.

D, use NAGSAG mnemonic – looking at which is soluble in water

Question 3.