Acids and Bases

H₃O⁺ is responsible for the  characteristic properties of an acid . The hydronium ion is a hydrogen ion in association with a molecule of water. In a water molecule, the oxygen atom has two pairs of unshared electrons in its outermost shell. The hydrogen ion does not have any electron in its valence shell. Hence, it shares a pair of electrons from the oxygen atom by means of co-ordinate co-valency to form a hydronium ion.

An acid salt is derived from an acid and base in which only a part of the hydrogen is replaced by a basic radical.In KHSO₄  only one H of Sulphuric acid has been replaced by K⁺ of KOH. Hence, it is an acid salt.

Arrhenius acid is a substance that when added to water it increases the concentration of H¹⁺ ions. So, HCl is an Arrhenius acid because when it is  added to water it  increases the concentration of H¹⁺ ions. 

In 1923, J.N.Bronsted and T.M.Lowry proposed a theory known as the Bronsted-Lowry proton transfer theory. According to this concept, any hydrogen species containing (a molecule, a cation or an anion), which is capable of donating one or more protons to any other substance, is called an acid. Acids classified on the basis of this concept are termed as Bronsted acids .

In a neutralisation reaction an acid gives H⁺ which combines with existing H₂O molecule and forms H₃O+.

Acetic acid (vinegar) is the primary ingredient used in preparing pickles.

An alkali is a  base that dissociates in water to yield hydroxyl ion OH^- as the only negative ions. Sodium hydroxide, potassium hydroxide and ammonium hydroxide are the common alkalis. All alkalis are base.

Neutralisation reaction is a chemical reaction in which an acid and a base react to form  salt & water.When strong acids and strong bases react, the products are salt and water. The acid and base neutralize each other, so the solution will be neutral having pH=7 and the ions that are formed will not react with the water.Depending on the solubility of the salt, it may remain in ionized form in the solution or it may precipitate out of solution.

Vinegar is a versatile liquid that results from the fermentation of ethanol. The key ingredient of vinegar is acetic acid, which gives it an acidic taste. While there may be additions of other kinds of acid like tartaric acid and citric acid, the typical pH of vinegar ranges anywhere from 2 to 3.5. In food preparation procedures, it is a multi-purpose product as an ingredient and condiment. Outside of cooking, vinegar has medicinal, household cleaning, and agricultural applications.

Citric acid is a weak organic acid found in citrus fruits. It is a natural preservative and is also used to add an acidic (sour) taste to food and soft drinks.It is acolorless translucent crystalline acid, with formula C₆H₈O₇, principally derived by fermentation of carbohydrates or from lemon, lime and pineapple juice. 

A dibasic acid has two acidic hydrogen atoms in its molecules which can be ionised. Sulphuric Acid, H₂SO₄, is a dibasic acid, because it contains two hydrogens atoms which ionise in aqueous solution to become Hydrogen Ions, H^+.

A molecule of Sulphuric Acid, H₂SO₄, consists of two atoms of hydrogen, one atom of sulphur and four atoms of oxygen.It is a colourless viscous & highly corrosive oily liquid.It is  a powerful dehydrating agent and is used to remove a molecule of Water from many organic compounds. It is widely used in the manufacture of chemicals, e.g., in making hydrochloric acid, nitric acid, sulfate salts, synthetic detergents, dyes and pigments, explosives, and drugs.It serves as the electrolyte in the lead-acid storage battery commonly used in motor vehicles.Acid for this use, contains about 33% H₂SO₄ with specific gravity about 1.25, is often called battery acid.

The reaction between acid and base is known as neutralisation reaction. According to Arrhenius theory of acid and base, in which a water solution of acid is mixed with a water solution of base to form a salt and water. This reaction is complete only if the resulting solution has neither acidic nor basic properties. Such a solution is called a neutral solution. Complete neutralization can take place when a strong acid, such as hydrochloric acid, HCl, is mixed with a strong base, such as sodium hydroxide, NaOH. Strong acids and strong bases completely break up, or dissociate, into their constituent ions when they dissolve in water. In the case of hydrochloric acid, hydrogen ions, H⁺, and chloride ions, Cl⁻, are formed. In the case of sodium hydroxide, sodium ions, Na⁺, and hydroxide ions, OH⁻, are formed. The hydrogen and hydroxide ions readily unite to form water. If the number of hydrogen ions in the hydrochloric acid solution is equal to the number of hydroxide ions in the sodium hydroxide solution, complete neutralization occurs when the two solutions are mixed. The resulting solution contains sodium ions and chloride ions that unite when the water evaporates to form sodium chloride.

A base that has three hydroxyl ions and can combine with three hydrogen ions, is known as a triacidic base. Example: Aluminium hydroxide

 An oxyacid is an acid that contains an oxygen  atom bonded to a hydrogen atom and at least one other elements.e..g.Sulfuric acid (H₂SO₄), phosphoric acid (H₃PO₄), and nitric acid (HNO₃) are all oxyacids.