Salt and It's Types

1. Baking Soda

Chemical Name: Sodium hydrogen carbonate

Molecular Formula: NaHCO3

Properties:

• Sodium hydrogen carbonate is commonly referred to as baking soda.

• Sodium hydrogen carbonate is used in the baking industry.

• Used to prepare soda acid.

• It is also used for foam type fire extinguishers.

2. Washing Soda:

Molecular Formula: Na2CO3.10H2O

Chemical Formula: Sodium carbonate Decahydrate

Add water to sodium carbonate and this allows the mixture to cool to form decahydrate sodium carbonate. This is often called washing soda.

Properties:

• It is solid with white crystals. It exists as a decahydrate of sodium carbonate.

• When exposed to dry air and heat you lose water molecules to convert to anhydrous form.

• It dissolves in water and during the heat of the dilution will come out.

3. Hydrated Salt:

• The molecules of salt that contain a fixed number of water molecules in them are called hydrated salts.

• They are usually present as they are relatively dry.

• These salts heat up and lose their water molecules and form waterless salt.

4. Plaster of Paris

Paris' plaster is chemically called calcium sulphate hemihydrate. As it is brought to use from Paris, it is called the "plaster of Paris". Prepared by heating gypsum at 373K.

Properties:

• Used as a bandage, proofing material, sealing agent.

• Used for making pictures, toys and decorative articles.

• It is also used to smooth out exposed surfaces.

5. Calcium Chloride

Calcium chloride (CaCl2) resembles table salt in its white colour. It is widely used to clear snow on roads. It works better than sodium chloride as a deicer, because calcium chloride produces three ions, while calcium chloride produces only two. Calcium chloride is hygroscopic, which is the ability to absorb water so that if you leave it in the room uncovered, it can absorb enough water from the air to dissolve into a solution by itself.

6. Copper Sulphate

Copper sulphate (CuSO4) is a blue salt made of copper, sulphur and oxygen. When it dissolves in water, it becomes coloured. If you dip a metal object in a mixture of copper sulphate and water, the metal will soon turn red. This is a copper film, due to the chemical reaction between the solution and the metal. The same reaction causes iron to replace copper in the solution, forming iron sulphate.

When is the Salt Solution Basic or Acidic?

There are a few guiding principles that summarise the result:

Salt from solid foundations and strong acids does not produce hydrolyze - The pH will remain neutral at 7. Halides and alkaline metals separate and do not affect H+ as the cation does not change H+ and the anion does not absorb H+ from water. That’s why NaCl is a neutral salt. Generally: Salt containing halides (excluding F-) and alkaline metal (excluding Be2+) will split into spectator ions.

Salt from a weak base and weak acid also produces hydrolyze like others, but it is complex and will require Ka and Kb to be considered. Any strong acid will be a controlling factor in determining whether it is Acidic or Basic. The cation will be Acidic, and the anion will form the basis and will form a hydronium ion or hydroxide ion depending on which ion is most sensitive to water.

More About the Topic

In chemistry, a salt is described as a chemical compound that consists of an ionic assembly of cations and anions. In general, salts are composed of related numbers of cations (which are positively charged ions) and anions (which are negatively charged ions) so that the product is defined as electrically neutral (without any net charge). These component ions are organic, such as acetate (CH3CO−2) are inorganic, such as chloride (Cl−); and can be monatomic, such as polyatomic or fluoride (F−), such as sulfate (SO2−4).

Examples of salt are given as CuCl2, NaCl, and more.

Acid + Base → Salt + water

Sodium chloride is the best-known salt, and one salt is referred to by almost everyone due to its widespread use every day.

Types of Salts

Let us look at different types of salt as listed below.

Acidic Salt - The salt that is formed by the partial neutralization of a polyprotic or diprotic acid is called acidic salt. These salts contain ionizable H+ ions along with another cation. Mostly the ionizable H+ comes under the part of an anion. A few acid salts can be used in baking.

For example, KH2PO4, NaHSO4­, and more.

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\[H_{2}SO_{4} + NaOH \rightarrow NaHSO_{4} + H_{2}O\]

Alkali or Basic Salt - The salt that is formed by the partial neutralization of a strong base by the weak acid is called a basic salt. These salts hydrolyze to produce a basic solution. This happens because when the hydrolysis of a basic salt occurs, the conjugate base of the weak acid is produced in the solution.

For example, White lead (2PbCO3·Pb(OH)2).

Double Salt - The salts which contain more than one cation or one anion are called double salt. These salts are obtained by the combination of two different salts that are crystallised in a similar ionic lattice.

For example, Potassium sodium tartrate (KNaC4H4O6.4H2O) is also called Rochelle salt.

Mixed Salts - The salt which holds a fixed proportion of two salts and often shares either a common cation or anion is called mixed salt.

For example, CaOCl2.

Properties of Salt

• Colour: Solid salts tend to be transparent, as represented by the sodium chloride compound. In most cases, the apparent transparency or opacity is only related to the difference in the size of the individual monocrystals. Since the light reflects from the grain boundaries (boundaries between the crystallites), the larger crystals tend to be as transparent, while the polycrystalline aggregates seem to be like white powders.

• Odour: Salts of both strong acids and strong bases ("which are referred to as strong salts") are non-volatile and often odourless, whereas the salts of either weak acids or weak bases ("which are referred to as weak salts") can smell as the conjugate acid (for example, vinegar and almonds) or the conjugate base (for example, ammonium salts such as ammonia) of the component ions.

• Taste: Various salts can elicit all 5 basic tastes, for example, sweet (lead diacetate, which causes lead poisoning when ingested), salty (sodium chloride), bitter (magnesium sulfate), sour (potassium bitartrate), and savoury (monosodium glutamate) or umami.

• Conductivity: Characteristically, salts are insulators. Molten salts or salt solutions conduct electricity. Due to this reason, liquified (molten) salts and the solutions consisting of dissolved salts (for example, sodium chloride in water) are referred to as electrolytes.

• Melting Point: Characteristically, salts contain high melting points. Suppose, sodium chloride melts at a temperature of 801°C. A few salts having low lattice energies are liquid near or at room temperature. These are the molten salts, which are usually mixtures of ionic liquids, and salts, which usually hold organic cations. These liquids represent unusual properties like solvents.

• Identification of Salts: By definition, if a compound is produced of either a cation or an anion, it is described as salt in chemistry.

The simplest salts are the compounds of a kind of metal cation having one kind of non-metal anion. If we look at the periodic chart, there is a dark stair-step line over on the right. The atoms that exist to the left of it are said to be metals, those to the right are said to be non-metals, and a few of those present on the steps (not aluminium) are called metalloids or semi-metals.

Compounds that hold a metal cation and a polyatomic anion are also called salts. At the same time, compounds that hold a polyatomic cation and an anion are also called salts.

Differentiation Between Acidic and Basic Salt

A basic salt holds the weak acid's conjugate base. Hence, acetate is described as the conjugate base of a weak acid's acetic acid. Thus, sodium acetate is basic.

An acidic salt contains the weak base's conjugate acid. Hence, the ammonium ion is described as the weak base of ammonia's conjugate acid. Thus, ammonium chloride would be the acidic salt.

The conjugate bases of strong acids (Cl- from HCl) and the conjugate acids from strong bases (Na+ from NaOH) are given as neutral and produce neutral salts such as NaCl.

Hydrolysis of Salt

An ionic molecule known as a salt is created when an acid and a base balance one another out. While salt solutions may appear to be always neutral, they can frequently be either acidic or basic. Consider the salt that results from the strong base sodium hydroxide neutralising the weak acid hydrofluoric acid. Below are equations of the molecular and net ionic equations.

                   HF+ NaOH → NaF + H2O

                    HF + OH- → F- + H2O

The sodium ion is a spectator ion in the neutralisation reaction because sodium fluoride is soluble. To a small degree, the fluoride ion can interact with water and accept a proton.

                   F- + H2O      ⇌        HF + OH- 

A weak Bronsted-Lowry base is being acted upon by the fluoride ion. The process described above results in the production of a hydroxide ion, which mildly basifies the solution. An acidic or basic solution is created when one of the ions from a salt combines with water in a process known as salt hydrolysis.

Interesting Facts 

• The history of salt traces back to as far as 6050 BC. Salt was used as part of religious offerings and to preserve mummies in Egypt. It was a valuable commodity traded between the Phoenicians and their Mediterranean empire.

• Salt is used to remove traces of water from aviation fuel after it is purified.

• There is about 35 grams of salts (mostly, sodium chloride) in a litre of seawater.

Key Features

• Salt hydrolysis is a reaction in which one of the ions from a salt reacts with water, forming either an acidic or basic solution.

• Salts of different cations and anions have different colours.

• A salt that is derived from the reaction of a strong acid with a strong base forms a solution that has a pH of 7.