Solubility rules-usually soluble

• Apply rules in order1. Acids (except long chain organics)

1. SA: HCl, HBr, HI, HNO3, H2SO4, HClO4

2. SA completely dissociate

2. All Na+, K+, NH4+, NO3

-, C2H3O2-

3. Most Cl-, Br-, I- (some exceptions)4. Most SO4

-2 (some exceptions)

Solublity rules –mostly insoluble5. Most S-

6. Most OH- CO3-2 SO3

-2 PO4-3

Strong Bases: Li, Na, K, Rb, Cs OH Ca, Sr, Ba, Ra (OH)2

strong bases completely dissociate

7. Gases – Elemental gases very slightly soluble– CO2 H2S SO2 slightly soluble– (bubble out of solution)– H2SO3 and H2CO3 break down in acidic soln

• See more detailed rule– Handouts– Book chart

Another way to look at the rules follows

• These are only for the most common compounds – there are obviously more rules (and exceptions!!!)

General Solubility rulesusually soluble

Soluble Compounds

• Salts of Na+ K+ NH4+

• Salts of Cl- Br- I-

• Salt of F-

• Salts of NO3- ClO3

- ClO4- and

C2H3O2-

• Salts of SO4-2

Exceptions

• Ag+ Hg2+2 Pb+2

• Mg+2 Ca+2 Sr+2 Ba+2 Pb+2

• Sr+2 Ba+2 Pb+2

General solubility rulesgenerally insoluble

Insoluble compounds• Salts of• CO3

-2

• PO4-3

• C2O4-2 (oxalate)

• CrO4-2

• S-2

• OH-1

• O-2

Exceptions

• Salts of NH4+ and all the

alkali metals (Group IA metals)

Medical applications

• Kidney stones are often calcium salts of slightly soluble compounds (we classified them as insoluble)– Phosphates– Carbonates– Oxalates

• Calcium oxalate crystals are needle like and would be extremely painful to excrete!! Whereas the phosphates and carbonates aren’t needle-like

Other medical applications

• A lot of drugs have poor solubilities as neutral molecules –

• Many of the drug molecules have acidic or basic groups

• If you react the acid molecules with NaOH – you can produce the sodium salt - usually with better solubility

• If you react the basic molecules (the amines) with HCl – you produce the chloride salt and usually increase the solubility

Example of these drugs

• Naproxen sodium (or sodium naproxen) the drug in Alleve – acid group reacts with NaOH to eliminate water leaving naproxen as an anion

• Naproxen-COOH + NaOH NaproxenCOO-Na+ + H2O

• Pseudoephedrine hydrochloride:a decongestant • PseudoephedrineNH2 + HCl

pseudoephedreinNH3+Cl-