Salts can be classified in a variety of ways. Salts that produce hydroxide ions when dissolved in water are called alkali salts. Salts that produce acidic solutions are acid salts. Neutral salts are those salts that are neither acidic nor basic. Zwitterions contain an anionic and a cationic centre in the same molecule, but are not considered to be salts. Examples of zwitterions include amino acids, many metabolites, peptides, and proteins.
Properties
Color
Solid salts tend to be transparent as illustrated by sodium chloride. In many cases, the apparent opacity or transparency are only related to the difference in size of the individual monocrystals. Since light reflects from the grain boundaries, larger crystals tend to be transparent, while the polycrystalline aggregates look like white powders. Salts exist in many different colors, which arise either from the anions or cations. For example:
sodium chloride, magnesium sulfate heptahydrate are colorless or white because the constituent cations and anions do not absorb in the visible part of the spectrum
Few minerals are salts because they would be solubilized by water. Similarly inorganic pigments tend not to be salts, because insolubility is required for fastness. Some organic dyes are salts, but they are virtually insoluble in water.
Taste
Different salts can elicit all five basic tastes, e.g., salty, sweet, sour, bitter, and umami or savory.
Odor
Salts of strong acids and strong bases are non-volatile and often odorless, whereas salts of either weak acids or weak bases may smell like the conjugate acid and cyanides like hydrogen cyanide ) or the conjugate base of the component ions. That slow, partial decomposition is usually accelerated by the presence of water, since hydrolysis is the other half of the reversible reaction equation of formation of weak salts.
Salts are characteristically insulators. Molten salts or solutions of salts conduct electricity. For this reason, liquified salts and solutions containing dissolved salts are called electrolytes.
Melting point
Salts characteristically have high melting points. For example, sodium chloride melts at 801 °C. Some salts with low lattice energies are liquid at or near room temperature. These include molten salts, which are usually mixtures of salts, and ionic liquids, which usually contain organic cations. These liquids exhibit unusual properties as solvents.
Nomenclature
The name of a salt starts with the name of the cation followed by the name of the anion. Salts are often referred to only by the name of the cation or by the name of the anion. Common salt-forming cations include:
Salts with varying number of hydrogen atoms replaced by cations as compared to their parent acid can be referred to as monobasic, dibasic, or tribasic, identifying that one, two, or three hydrogen atoms have been replaced; polybasic salts refer to those with more than one hydrogen atom replaced. Examples include:
An acid and a base anhydride, e.g., 2 HNO3 + Na2O → 2 NaNO3 + H2O
In the salt metathesis reaction where two different salts are mixed in water, their ions recombine, and the new salt is insoluble and precipitates. For example:
: Pb2 + Na2SO4 → PbSO4↓ + 2 NaNO3
Strong salt
Strong salts or strong electrolyte salts are chemical salts composed of strong electrolytes. These ionic compounds dissociate completely in water. They are generally odorless and nonvolatile. Strong salts start with Na__, K__, NH4__, or they end with __NO3, __ClO4, or __CH3COO. Most group 1 and 2 metals form strong salts. Strong salts are especially useful when creating conductive compounds as their constituent ions allow for greater conductivity.
Weak salt
Weak salts or "weak electrolyte salts" are, as the name suggests, composed of weak electrolytes. They are generally more volatile than strong salts. They may be similar in odor to the acid or base they are derived from. For example, sodium acetate, NaCH3COO, smells similar to acetic acid CH3COOH.
