Acids and Bases

Bookmark added to your notes.
View Notes
×

What are Acids and Bases?

The acid definition is given as any hydrogen that contains a substance capable of donating a proton (a hydrogen ion) to the other substance. A base is an ion or molecule that is able to accept a hydrogen ion from an acid.

Usually, the acidic substances are identified with their sour taste. Basically, an acid is a molecule that can donate an H+ ion and also can remain energetically favorable after a loss of H+ ion. Acids are much known to turn blue litmus into the red.

On the other side, bases are characterized by a slippery texture and a bitter taste. A base that is dissolved in water is known as an alkali. When these substances react chemically with acids, they further yield salts. Besides, the bases are much known to turn red litmus into blue.


Theories of Acids and Bases

There are 3 different theories that have been put forth to define these acids and bases. These 3 theories include:

  1. Arrhenius Theory

  2. Bronsted-Lowry Theory

  3. Lewis Theory of Acids and Bases.

A brief description of these theories is provided below. As discussed, acids and bases are defined via three different theories.

  1. Coming to the Arrhenius theory of acids and bases, it is stated that “an acid generates the H+ ions in a solution, and a base produces an OH ion in its solution.”

  2. The theory of Bronsted-Lowry explains “an acid as a proton donor; a base as a proton acceptor.”

  3. And finally, the Lewis theory of acids and bases says “acids as electron-pair acceptors and the bases as electron-pair donors.”


pH of Acids and Bases

To find the numeric value of the acidity or basicity level of a substance, the pH scale (pH stands for ‘potential of hydrogen’) can be used. Here, the pH scale is the most common and trusted procedure to measure how acidic or basic a substance is. Also, a pH scale measure can differ from 0 to 14, where 14 is the most basic, and 0 is the most acidic a substance can be.

The other way to check if a substance is acidic or basic is by using a litmus paper. There exist two types of litmus paper available, used to identify the acids and bases. They are the red litmus paper and the blue litmus paper. The blue litmus paper changes red under acidic conditions, whereas the red litmus paper turns blue under alkaline or basic conditions.


Properties of Acids and Bases

Properties of Acids

  • Acids are good conductors of electricity.

  • They are corrosive in nature.

  • When reacted with metals, acid substances produce hydrogen gas.

  • Always, their pH values are less than 7.

  • Acids are sour-tasting substances.

  • Examples of acids are Hydrochloric acid [HCl], Sulfuric acid [H2SO4], Acetic acid [CH3COOH], and more.

[Image will be uploaded soon]

Properties of Bases

Some of the properties, such as a bitter taste, are owned by all bases. The bases also feel slippery. You can dream about what slippery soap looks like, and this is a foundation. Also, bases conduct electricity when immersed in water because they consist of charged particles in the solution.

  • Bases are found to have a soapy texture when we touch them.

  • When dissolved in water, these substances release hydroxide ions (OH ions) 

  • Bases act as good conductors of electricity in their aqueous solutions

  • Always, the pH values corresponding to the bases are greater than 7.

  • Bases are bitter-tasting substances, having the ability to turn red litmus paper into blue.

  • Examples can be given as milk of magnesia [Mg(OH)2], Sodium Hydroxide [NaOH], Calcium Hydroxide [Ca(OH)2], and more.


Neutral Substances

These are the substances, which have no properties of either acid or base, which has a similar amount of hydroxyl ions and hydrogen ions, and they do not modify the color of the litmus surface.

  • Neutral substances do not display any acidic or basic characteristics.

  • Their pH values approximately 7.

  • Neutral substances have no effect on blue or red litmus paper.

  • pH of pure water is exactly 7.

  • Examples are Common salt (NaCl), Water, and more.


Uses of Acids and Bases

Various uses of acids and bases can be listed as follows:

Uses of Acids

  • Vinegar, which is a diluted solution of acetic acid, has different household applications. It is used primarily as a food preservative.

  • Citric acid is an integral part of orange juice and lemon juice. It is also used as a food preservative.

  • Sulfuric acid is more widely used in batteries. Commonly, the batteries used to start automobile engines contain this acid.

  • The industrial production of dyes, explosives, paints, and fertilizers involves the use of nitric acid and sulfuric acid.

  • Phosphoric acid is a primary ingredient in various soft drinks.

Uses of Bases

  • The manufacturing of paper and soap involves the use of sodium hydroxide. Also, NaOH is used in the manufacturing of rayon.

  • Ca(OH)2, which is also called calcium hydroxide or slaked lime, is used to manufacture the bleaching powder.

  • Dry mixes used in decoration or painting are made using a limited amount of calcium hydroxide.

  • Magnesium hydroxide, also called the milk of magnesia, is most commonly used as a laxative. It also reduces if there is any excess acidity in the human stomach and is, thus, used as an antacid substance.

  • Ammonium hydroxide is an important reagent that is used in laboratories.

  • Any excess acidity in soils is neutralized by employing the slaked lime.

FAQ (Frequently Asked Questions)

1. Distinguish between Acids and Bases?

Ans. 

Acids

Bases

Acid gives off hydrogen ions when it is dissolved in water.

Bases give off hydroxyl ion when they are dissolved in water.

It changes blue color litmus paper into the red.

It changes red color litmus paper into the blue.

It is sour in taste.

It is bitter in taste, whereas, soapy to touch.

The pH value of acid ranges from 1 to 7.

The pH value of bases ranges from 7 to 14.

Examples are H2SO4, HCl, and more.

Examples are KOH, NaOH, and more.

2. Explain Acids and Bases in Arrhenius Concept?

Ans. 

  • The Swedish scientist named Svante August Arrhenius defined acids as the substances that increase the H+ ion concentration of water when dissolved in it.

  • These protons travel to form hydronium ions (H3O+) by combining them with water molecules.

  • In the same way, the Arrhenius definition of a base explains that bases are the substances, increasing the concentration of OH ions when dissolved in water in it.

  • A merit of this theory is that it explains the reaction between acids and bases successfully that yield salts and water.

  • And the important limitation of the Arrhenius definitions of acids and bases is that it fails in explaining how substances lacking hydroxide ions produce basic solutions when dissolved in water, such as F, and NO2–.

3. List the main difference between Acid and Base?

Ans. The two types of corrosive compounds are acids and bases. Any material having a pH value between 0 & 7 is called acidic while a pH value between 7 & 14 is a base. Acids are the ionic compounds that break apart to produce a hydrogen ion ( H+) in water.

4. What is the importance of Acid?

Ans. Acids play an important role within the human body. The hydrochloric acid presence in the stomach helps for the digestion by breaking down complex food molecules. Amino acids are needed for protein synthesis that are needed to grow and repair the body tissues.