Acids and Bases - Definition, Properties, Examples, FAQs

To discuss the properties of acids and bases we first have to study about what acid and base are.
Acid: The word acid comes from the Latin word acidus, which means "sour taste." When acidic chemical compounds dissolve in water, they produce a sour or acidic flavor. Even after the loss of a hydrogen ion from its molecule, an acid can remain energetically favorable.

Acids cause litmus to turn Red. The pigment in the litmus paper reacts with the H⁺ ions, causing chemical modifications in which the chemical bonds are tuned to reflect longer wavelength light, giving it a red appearance to human eyes. The absorption of blue to green wavelengths occurs when the pigment in litmus paper reacts with the H⁺ ions in an acid. Acids mostly oxidize other chemical molecules or alter the color of a product. Acids can be organic or inorganic, with the former having a carboxyl group, hydroxyl group, and hydrogen atoms, while the latter has a metal ion.

Bases: Bases are distinguished by their slick texture and harsh flavour. Alkali is a term used to describe bases that can dissolve in water. The chemical reaction of bases reacting with acids to produce salt and water is known as neutralization.

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Bases turn to be a reddish-blue colour in the presence of litmus. The following is the explanation behind the colour change: The OH^- ions, or hydroxyl ions, react with the colour in the litmus paper in distinct ways. When it reacts with the hydroxyl ion, it absorbs green and red wavelengths and reflects short wavelengths, giving it a blue colour.

The colour of the indicators can be changed by the bases. In the presence of a base, phenolphthalein turns pink.

Other than these acids and bases can also be differentiated on the basis of pH value if any solution shows pH value less than 7 then it is said to be acidic nature and if it is greater than 7 then solution is said to be of basic nature while if the pH shown by solution is exactly 7 then it is said to be of neutral nature. Acid and base combine to form salt and water. Salts are formed when an acid and a base react, which is known as a neutralization reaction. Salts are ionic compounds made up of a cation and an anion, where the cation is not H+ and the anion is not OH^-.

Physical and chemical properties of acids and bases can be discussed as follows:

1. Physical properties of acids and bases: Physical properties of acids and bases generally depend upon their looks like their color, solubility, taste and appearance.

a. Color: Mineral acids are colorless liquids, however impurities in sulphuric acid can cause it to turn yellow. Some organic acids are solids with a white color while bases are colorless in nature except hydroxide of copper and iron.

b. Taste: Acids are basically sour in taste like citric acid while bases are of bitter taste.

c. Touch: Acids have no particular touchy appearance while bases are slippery to touch.

d. Solubility: Acids are generally soluble in water while bases are not soluble in water.

Many acids are toxic if consumed and should not be tasted. The acid becomes a neutral chemical after it binds to the base. This reaction frequently results in the formation of water and salt. When strong acids react with strong bases, this is a common occurrence. The acids are the generators of electricity. The batteries are utilized to generate electricity outside of this. A strong acid is one that conducts electricity well, while a weak acid is one that conducts electricity poorly.

Chemical properties of acids and bases

Chemical properties generally based on the chemical reactions of acids and bases with other metals or gases

a. Reaction of acids and bases with metals:

When a metal reacts with an acid, hydrogen is usually displaced from the acid. Hydrogen gas is formed as a result of this process. The metals react with the residual acids to generate a salt. For instance, consider the reaction of sulphuric acid with zinc.

The metal reacts with alkalis (water-soluble bases) to form salt and hydrogen gas. To explain this we can take the example of zinc reacting with sodium hydroxide

b. Reaction of acids with carbonates and bicarbonates of metals

Salt, carbon dioxide, and water are produced when metal carbonates/metal bicarbonates react with acids. For instance, sodium carbonate/sodium bicarbonate reacts with hydrochloric acid. Metal carbonate react with acid is shown in the following example:

While bases will not react with metal carbonate or metal bicarbonate.

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c. Metal oxides and non-metal oxides with acids and alkalis

Salt and water are produced when metal oxides react with acids. For instance, consider the reaction between copper oxide and weak hydrochloric acid.

Metal oxides reacts with acids while in case of bases non-metal oxides react with them and form salt and water. Reaction between non-metal oxide and base can be shown as:

d. Base and acid reactions with each other

Acids and bases react with each other and produce salt and water. Neutralization reactions are the reactions that occur when acids and bases react to form salts. For this instance we can take the example of a reaction occurring between sodium hydroxide and hydrochloric acid.

The reaction of an acid and a base always produces salt and water, which is known as neutralization. One H+ ion of acid is neutralized by one OH– ion of base in a neutralization process. Complete neutralization occurs when all of the H+ ions in the acidic solution are neutralized by the corresponding number of OH– ions in the basic solution. The total number of H+ and OH– ions produced by each acid and base determines the relative amounts of acid and base necessary for full neutralization.

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NCERT Chemistry Notes:

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