sodium chromate is yellow by virtue of the chromate ion
potassium dichromate is orange by virtue of the dichromate ion
cobalt nitrate is red owing to the chromophore of hydrated cobalt(II) ([Co(H2O)6]2+).
copper sulfate is blue because of the copper(II) chromophore
potassium permanganate has the violet color of permanganate anion.
nickel chloride is typically green of [NiCl2(H2O)4]
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 (sodium chloride), sweet (lead diacetate, which will cause lead poisoning if ingested), sour (potassium bitartrate), bitter (magnesium sulfate), and umami or savory (monosodium glutamate).
Odor
Salts of strong acids and strong bases ("strong salts") are non-volatile and often odorless, whereas salts of either weak acids or weak bases ("weak salts") may smell like the conjugate acid (e.g., acetates like acetic acid (vinegar) and cyanides like hydrogen cyanide (almonds)) or the conjugate base (e.g., ammonium salts like ammonia) 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.
Solubility
See also: Solubility § Solubility of ionic compounds in water
Many ionic compounds exhibit significant solubility in water or other polar solvents. Unlike molecular compounds, salts dissociate in solution into anionic and cationic components. The lattice energy, the cohesive forces between these ions within a solid, determines the solubility. The solubility is dependent on how well each ion interacts with the solvent, so certain patterns become apparent. For example, salts of sodium, potassium and ammonium are usually soluble in water. Notable exceptions include ammonium hexachloroplatinate and potassium cobaltinitrite. Most nitrates and many sulfates are water-soluble. Exceptions include barium sulfate, calcium sulfate (sparingly soluble), and lead(II) sulfate, where the 2+/2− pairing leads to high lattice energies. For similar reasons, most metal carbonates are not soluble in water. Some soluble carbonate salts are: sodium carbonate, potassium carbonate and ammonium carbonate.
Conductivity
Edge-on view of portion of crystal structure of hexamethyleneTTF/TCNQ charge transfer salt.[3]
Salts are characteristically insulators. Molten salts or solutions of salts conduct electricity. For this reason, liquified (molten) salts and solutions containing dissolved salts (e.g., sodium chloride in water) 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 (e.g., sodium or ammonium) followed by the name of the anion (e.g., chloride or acetate). Salts are often referred to only by the name of the cation (e.g., sodium salt or ammonium salt) or by the name of the anion (e.g., chloride salt or acetate salt).
Common salt-forming cations include:
Ammonium NH+
4
Calcium Ca2+
Iron Fe2+
and Fe3+
Magnesium Mg2+
Potassium K+
Pyridinium C
5H
5NH+
Quaternary ammonium NR+
4, R being an alkyl group or an aryl group
Sodium Na+
Copper Cu2+
Common salt-forming anions (parent acids in parentheses where available) include:
Acetate CH
3COO−
(acetic acid)
Carbonate CO2−
3 (carbonic acid)
Chloride Cl−
(hydrochloric acid)
Citrate HOC(COO−
)(CH
2COO−
)
2 (citric acid)
Cyanide C≡N−
(hydrocyanic acid)
Fluoride F−
(hydrofluoric acid)
Nitrate NO−
3 (nitric acid)
Nitrite NO−
2 (nitrous acid)
Oxide O2−
Phosphate PO3−
4 (phosphoric acid)
Sulfate SO2−
4 (sulfuric acid)
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:
Sodium phosphate monobasic (NaH2PO4)
Sodium phosphate dibasic (Na2HPO4)
Sodium phosphate tribasic (Na3PO4)
Explanation:
