Salt: Preparation, Properties, Types, Uses

Salt

Salt is defined in chemistry as an inorganic or organic molecule with ionic bonding. When dissolved in water, ions break down into positively charged cations and negatively charged anions. Positive ions (cations) and negative ions (anions) make up salts. Because a cation is a metallic ion formed from a base, it is referred to as a basic radical. Because anion is produced from an acid, it is referred to as an acid radical. Ionic solutions are thus perfect electrolytes that may easily conduct electricity.

Salts are frequently formed as a result of acid-base neutralization reactions. For example, the neutralization reaction between hydrochloric acid and sodium hydroxide can yield sodium chloride, as illustrated in the balanced chemical equation below.

Preparation of salt

Salts can be soluble or insoluble in water. The procedures for preparing salts are based on their solubility in water. Salts can be soluble or insoluble in water. The methods used to prepare salts are based on their water solubility.

  • By reaction of acid and metal (Direct displacement method)

This is a direct displacement approach in which an acid’s hydrogen ion is replaced by a reactive metal such as Calcium, magnesium, zinc, and iron.

  • By reaction of acid and base (Neutralization reaction)

When an acid combines with a base, salt is produced. The neutralization reaction is the name given to this reaction. This reaction produces a salt that contains a cation from the base and an anion from the acid reagent.

  • Reaction of acid and metallic oxide

The insoluble metallic oxides primarily react with dilute acids to form salt and water.

  • Reaction of acid with carbonates and bicarbonates

Salts are generated when acids react with carbonates and bicarbonates. Since the salts are in an aqueous solution, physical methods can be used to separate them.

  • Insoluble salts preparation

Typically, soluble salt solutions are combined in this approach. During the process, ionic radicals exchange (i.e., metallic radicals exchange with acidic radicals) to form two new salts. One salt is insoluble, whereas the other is soluble. The insoluble salt precipitates (becomes solid in solution).

Properties of salts

  • When it comes to taste, color, smell, solubility, conductivity, and melting point, salts differ. These properties are determined by the salt’s composition and crystalline structure.
  • Although many salts have a distinct “salty” flavor, others have a completely distinct flavor. Lead diacetate, for example, can taste pleasant but is dangerous. Magnesium sulfate, on the other hand, tastes harsh, but potassium bitartrate tastes sour. Monosodium glutamate has a savory flavor that enhances the flavors of other food ingredients.
  • Many salts are clear or translucent, but some are opaque. The arrangement or structure of the monocrystals determines the opacity, transparency, and color of salts. Salts occur in a variety of colors, depending on their ionic composition. Cobalt nitrate, for example, is red due to the presence of hydrated cobalt (l l), but copper sulfate is blue due to the presence of copper (II) chromophore.
  • Odorless salts are created via neutralization reactions between strong acids and strong bases. Those that are generated from a weak acid and a strong base, or vice versa, have a distinct odor. Cyanide salts, which are generated from hydrogen cyanide, are the most prevalent. They have a characteristic almond aroma.
  • Because salts are ionic compounds, the majority of them are highly soluble in water and other types of solvents. Ammonium hexachloroplatinate, potassium cobaltinitrite, and most metal carbonates are exceptions.
  • Because of their ionic and polar characteristics, molten salts and salt solutions conduct electricity.
  • Because of their strong ionic interactions, salts have high melting points. The melting point of regular table salt, for example, is 801 degrees Celsius.

Types of salts

Simple salt

Simple salts are generated by the simple interaction of an acid and a base. The most known example of a simple salt is NaCl, which is formed from HCl (acid) and NaOH (base). Simple salts are further categorized into three categories of salts based on the precursor for the salts: acidic salts, basic salts, and neutral/normal salts.

Acidic salt

Acidic salts are formed when a strong acid reacts with a weak base. As a result of the inadequate neutralization of the acids, the salts have a pH of less than 7 and exhibit acidic characteristics. Because of inadequate neutralization, these salts contain one or more replaceable hydrogen atoms. E.g. Sodium carbonate (NaHCO3), Sodium bisulfate (NaHSO4, Monosodium dihydrogen orthophosphate (NaH2PO4)

Basic salt

Basic salts are formed by the reaction of a strong base and a weak acid. As a result of the partial neutralization of the bases, the salts have a pH greater than 7 and have alkaline characteristics. These salts are typically made up of one or more hydroxyl ions. For example,  Sodium hydroxide (NaOH), potassium cyanide (KCN), and zinc chloride hydroxide (Zn(OH)Cl)

Double salt

Double salts contain more than one cation or anion. It results from the interaction of two simple salts, and the resulting formula is often quite complicated. Double salts are addition compounds that are stable in solid form but release constituent ions when dissolved in water or any other ionic solvent. The unique features of the constituent ions are not lost in these compounds. Thus, double salts retain their identity when solid, but lose it when dissolved in water and dissociate into respective ions. For example: Potassium cerium fluoride (KCeF4), Mohr’s salt ((NH4)2Fe(SO4)2. 6 H2O), Potash alum (K2SO4Al2(SO4)3. 24 H2O).

Mixed Salt

Mixed salts are made up of two anions that share a cation or two cations that share an anion. These salts are formed when more than one acid or base reacts, resulting in an imbalance in the number of cations or anions. For example, Bleaching powder (Ca(ClO)2), Calcium disodium EDTA.

Complex salt

Complex salts are made up of both ions and molecule compounds. It typically consists of a central metal atom surrounded by neutral molecules and charged ions. These are the addition compounds that do not give up all of their constituent ions when dissolved in water. Complex salts retain their identity in solution. These compounds retain their identity in both solid and solution forms. For example: Tetra amino cupric sulfate ([Cu(NH3)4]SO4), Potassium ferrocyanide (K4[Fe(CN)6]).

Uses of Salt

  • Sodium chloride (NaCl) is a common table salt and cooking ingredient. It is also used to de-ice roads in the winter and to make sodium metal, caustic soda, and washing soda.
  • Sodium carbonate and soda ash are used to make glass, detergents, pulp and paper, and other chemicals.
  • Sodium sulfate is used in the production of glass, paper, and detergents.
  • Sodium silicate is used to make detergents, cleaning agents, and adhesives.
  • The chemical sodium chlorate is used in the production of explosives, polymers, and other compounds.
  • Sodium tetraborate is used in the leather industry for soaking and cleaning hides, as well as in the production of heat-resistant glass (pyrex), glazes, and enamels.
  • Calcium chloride is used in the winter to de-ice roadways, as a drying agent for chemical reagents, and as a freezing agent.
  • Calcium oxide (Cao) and quick lime are used as drying agents for gases and alcohol, as well as in steel production, water treatment, and the manufacture of other chemicals such as slaked lime, bleaching powder, and calcium carbide. To purify sugar, a Cao and NaOH mixture known as soda lime is used to eliminate carbon dioxide and water vapors from the air.
  • Gypsum is used as a fertilizer and to make plaster of Paris, which is used to make statues, casts, and other products.

References

  • https://psiberg.com/salts-in-chemistry/
  • https://www.vedantu.com/chemistry/salt
  • https://www.reagent.co.uk/blog/types-of-salts-in-chemistry-and-their-uses/
  • https://unacademy.com/content/nda/study-material/chemistry/salts-different-types-of-salts/#:~:text=Salt%20is%20classified%20into%20different,strong%20acid%20and%20base%20react.
  • https://www.elearn.gov.pk/onlinepdf/chemistry/10chemistry/pdfEng/chapter10.pdf
  • https://byjus.com/chemistry/salts-types-hydrolysis/

About Author

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Kabita Sharma

Kabita Sharma is a graduate student from the central department of chemistry, Tribhuvan University. She has been actively involved in research related to natural products, computational chemistry, and nanochemistry. She is currently working on enzyme assay, molecular docking, and molecular dynamic simulation.

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