Salt (chemistry)

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) can be used as 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⁺
  
• 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
  )
• hydrocyanic acid
  )
• Fluoride F⁻
  (hydrofluoric acid)
• Nitrate NO⁻
  ₃ (nitric acid)
• Nitrite NO⁻
  ₂ (nitrous acid)
• Oxide O²⁻
  (water)
• 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)

Formation

Solid lead(II) sulfate (PbSO₄)

Salts are formed by a chemical reaction between:

• A base and an acid, e.g., NH₃ + HCl → NH₄Cl
• A metal and an acid, e.g., Mg + H₂SO₄ → MgSO₄ + H₂
• A metal and a non-metal, e.g., Ca + Cl₂ → CaCl₂
• A
  NaOH + Cl₂O → 2 NaClO + H₂O
• 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:

  Pb(NO₃)₂ + 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.^{[citation needed]}

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, CH₃COONa, smells similar to acetic acid CH₃COOH.

See also

• Bresle method (the method used to test for salt presence during coating applications)
• Carboxylate
• Fireworks/pyrotechnics (salts are what give color to fireworks)
• Halide
• Ionic bonds
• Natron
• Salinity

References