Acid and Base Difference: Definition, Properties, Examples, Practice Problems and FAQs

Have you ever wondered why lemon tastes sour while soda tastes bitter?

Well, this is due to the acidic nature of lemon juice and the basic nature of soda. Differentiating between common acidic and basic substances such as lemon juice, tamarind, soda etc is quite easy. 

How would you distinguish whether a substance is acidic or basic if two unknown liquid samples are given to you?

One of the best methods is to use acid-base indicators such as litmus paper, phenolphthalein or methyl orange indicators.

What if there are no indicators available in the laboratory? How would you identify them in this scenario?

In this case, we have to study their chemical properties. Let’s understand some of the concepts of acid and base, and their chemical properties and will see the differences between acids and bases. 

Table of Content

• Concept of Acids and Bases
• Properties of Acids
• Properties of Bases
• Difference Between Acids and Bases
• Practice Problems
• Frequently Asked Questions - FAQs

Concept of Acids & Bases

The substances which are sour in taste are called acids and the substances which are bitter in taste are bases. But this is not always true. Moreover, determining any chemical with taste is not an appropriate method to distinguish between acids and bases. It is highly dangerous. Hence, several new methodologies were discovered. Depending on how one chooses to see the characteristics of acidity and basicity, the terms acid and base have been defined in a variety of ways. 

There are three different theories that have been put out to characterise acids and bases. These theories include the Arrhenius theory of acids and bases, Bronsted-Lowry theory and Lewis theory of acids and bases.

Arrhenius Theory:

The Arrhenius theory states that an acid is a substance that releases an ion when dissolved in water. It raises the amount of ions present in the solution. The base is a substance that dissolves in water and furnishes the ions. It raises the amount of ions present in the solution.

Example of an acid:

undergoes a dissociation reaction to produce and ions when dissolved in water. Due to this the concentration of ions is increased.

Example of a base:

undergoes a dissociation reaction to produce and ions when dissolved in water. Due to this, the concentration of ions is increased.

Bronsted-Lowry Theory:

The base is a substance that accepts an ion or a proton to form its conjugate acid, and the acid is a substance that donates an ion or a proton to form its conjugate base, according to the Bronsted-Lowry theory.

Examples:

(Here, is an acid and is its conjugate base)

(Here, is an acid and is its conjugate base)

Examples:

(Here, is a base and is its conjugate acid)

(Here, is a base and is its conjugate acid)

Lewis Theory:

According to the Lewis definition, bases are described as molecules or ions that can donate the unshared electron pairs while the molecules or ions that can accept the unshared electron pairs are acidic in nature.

Lewis acids:

• A Lewis acid can be an atom, ion, or molecule with an incomplete octet of electrons. For instance, .
• Lewis acids are defined as molecules with a central atom that can accept electrons.

Lewis bases:

• Lewis bases can be any molecule, atom, or ion with unshared pair of electrons. Lewis bases, , , etc. are a few examples.
• Anions function as Lewis bases because they can donate electrons. Examples include etc. 

Properties of Acids

• Acids can cause corrosion.
• They are effective electrical conductors in an aqueous solution.
• pH readings for an aqueous acidic solution are lower than 7.
• These chemicals release hydrogen gas when they come into contact with metals.
• Acids are sour in taste.
• Acids turn blue litmus paper into the red.
• Sulfuric acid [] and hydrochloric acid [] are two examples of acids.

Properties of Bases

• When touched, they are supposed to feel soapy.
• Bases are well known for being effective electrical conductors in aqueous solutions.
• pH readings for aqueous basic solutions are greater than 7.
• Bases have a strong, pungent flavour that turns red litmus paper to blue.
• Examples include calcium hydroxide and sodium hydroxide

Difference between Acid & Base

Parameters	Acids	Bases
Definition	According to Arrhenius theory, an acid is a substance that releases ions when dissolved in water.   According to Bronsted-Lowry theory, an acid is a substance that donates an ion or a proton to form its conjugate base.   According to the Lewis theory, acids are substances which accept electrons.	According to Arrhenius theory, the base is a substance that dissolves in the water and furnishes the   ions.    According to Bronsted-Lowry theory, a base is a substance that accepts an ion or a proton to form its conjugate acid.   According to the Lewis theory, bases are the substances which donate the unshared pair of electrons.
Litmus test	Acids cause blue litmus paper to turn red.	Bases cause red litmus paper to turn blue.
Flavour	Acids are sour in taste.	Bases taste bitter and feel soapy when touched.
pH range
Examples	, etc.	etc.

Practice Problems

Q 1 According to Arrhenius theory any molecule that loses proton is: 

a. an acid 
b. a base
c. a salt 
d. None of the above

Answer: (A)

According to Arrhenius theory, any molecule that releases protons in its aqueous solution is an acid. Hence, option A is the correct choice.

Q 2 Acid changes blue litmus paper into_____ 

a. Red
b. Violet
c. Green
d. white

Answer: (A)

Acid causes blue litmus paper to turn red whereas base turns red coloured litmus paper top blue. Hence, option A is the correct choice.

Q 3 Which of the following is not a lewis acid?

a. 
b. 
c. 
d. 

Answer: (C)

A molecule must lack electrons in order to be acidic in the Lewis sense, and it must be able to share electrons in order to be basic. , , are Lewis acids as these three have the capacity to accept the electrons, whereas is a Lewis base because it can donate the electrons. Hence, option D is the correct choice.

Q 4 Which of the following is not a property of base?

a. When touched, they are supposed to feel soapy.
b. Bases have pH readings typically lower than 7.
c. Bases have pH values higher than seven.
d. Bases turn red litmus paper blue.

Answer: (B)

Bases have the following properties:

• When touched, bases feel soapy.
• Bases are well known for being effective electrical conductors in aqueous solutions.
• Bases have pH values higher than seven.
• Bases turn red litmus paper blue.

pH reading is lower than 7 for acidic substances. Hence, option B is the correct choice.

Frequently Asked Questions - FAQs

Q1. What happens when an acid and a base are combined?
Answer: When an acid and a base are combined, they react to neutralise each other's effects and produce salt and water. Water is formed when the anion of the base and the cation of the acid combine. 

For example:

Q2. Can we mix acid with water?
Answer: When water is added to the concentrated acid. The solution boils violently, sputtering concentrated acid. After some time a very diluted solution results and the little heat that is released is insufficient to cause it to vaporise and spatter. So, water easily mixes with the acid and forms a diluted solution of acid. 

Q3. Is coffee a base or an acid?
Answer: The majority of coffee varieties have an acidic pH range of 4.85 to 5.10. The brewing process releases many acidic substances (Malic, lactic, quinic, phosphoric, linoleic, chlorogenic, acetic, and palmitic acids) among the countless other compounds in this beverage, which give it a distinctive flavour profile.

Q4. Can you name any bases found in the human body?
Answer: Adenine, Cytosine, Guanine, and Thymine are the four distinct nitrogen-based bases found in DNA (a complex nucleic acid found in cells). The genetic makeup of all human life is determined by various combinations of these four bases.

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