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Water-soluble compounds
when dissolved in water may dissociate into
ions. Compounds that dissociate completely (only ions are present in
solution) are called strong electrolytes. Compounds that
dissociate partially (both molecules and ions are present in solution)
are called weak electrolytes. Compounds that do not dissociate
into ions (only molecules are present in solution) are called
non-electrolytes.
General rules for
distinguishing to which category a given compound belongs are
summarized in the table below.
| Class
|
Description |
Members of
the class |
|
Strong electrolytes |
| all
water-soluble ionic compounds (salts) |
ionic compounds
have a metallic or ammonium (NH4+) cations,
and nonmetallic anions (there are metallic oxyanions known, for
example, MnO4-,
CrO42-) |
NaCl, CaCl2,
KSO4, ZnClO4, NH4NO3
and countless other |
| strong acids |
molecular
compounds that dissociate in water completely giving H+
ions (H3O+), and the corresponding anions |
HCl, HBr, HI,
HClO3, HClO4, HNO3, H2SO4
(only those listed) |
| strong bases |
molecular
compounds that dissociate in water completely giving HO-
ions and the
corresponding cations |
LiOH, NaOH, KOH,
RbOH, CsOH, Ca(OH)2, Sr(OH)2, Ba(OH)2
(only those listed) |
|
Weak
electrolytes |
|
weak acids |
molecular compounds that dissociate in
water only partially to give some H+ ions (H3O+),
the corresponding anions |
HF, HNO2, HCN, HClO, H2SO3, H3PO4and
other inorganic acids, acetic
acid (CH3CO2H) and other organic carboxylic
acids |
|
weak bases |
molecular compounds that dissociate in
water partially to yield some HO-
ions and the
corresponding cations |
NH3, CH3NH2
and other organic amines |
|
Non-electrolytes |
| covalent
molecular compounds (non ionic) |
molecular
compounds that do not dissociate into ions |
many
water-soluble organic compound, such as alcohols, aldehydes, ketones, sugars,
inorganic non-ionic compounds of non-metals |
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