Acid, Base, and Salt- Definition, Properties, Types, Uses, Practice problems, FAQs

Acids and bases are often among the first words that come to mind when thinking about chemistry. Everyone loves sour lemon, in the summer season. We all know bitter gourd has multiple benefits for our bodies. The nature of soap, detergents, and hand wash liquids are soapy to touch. Unknowingly, we use many acids, bases, and salt in our daily life: lemons, tamarind, soaps, bitter gourd, baking soda, table salt, and so on. You have also categorized them.

Let us brush our memory and learn much more.!!

Table of contents

• Acid
• Base
• Salt
• Limitations of this perception-Based definition of Acids, Bases and Salt
• Practice Problems
• Frequently Asked Questions – FAQs

Acid

Any substance that tastes sour, turns blue litmus paper red, combines with bases to form salts is referred as an acid.

Properties of Acids

• Aqueous solutions conduct electricity.
• Reaction with active metals liberate hydrogen gas.
• Reacts with metal carbonates (MCO3) and metal bicarbonates (MHCO3) and liberates CO2.

• Reacts with a metal oxide to farm salt and water.

Metal oxide + Acid → Salt + Water 

• Are corrosive in nature. 

Types of Acids

Organic Acid (Weak Acid)

The acidic substances present in plants and animals are organic acids. They are less corrosive and less reactive and hence are weak acids.

Mineral Acid (Strong Acid)

The acid prepared from the minerals of the earth is called mineral acids. They are highly corrosive and reactive and hence are strong acids

Uses of Acid

Sulphuric acid and nitric acids are widely used in the manufacture of fertilizers like ammonium sulfate and ammonium nitrate respectively. Hydrochloric acids are used for removing oxide film from steel objects (before they are galvanized).

Acetic acid (vinegar) is used to enhance the taste of food. Citric (lemon) is used as a food preservative. Phosphoric acid is used as a key ingredient in many soft drinks.

Base

Any substance that tastes bitter, soapy to touch, turns red litmus paper blue, and combines with acids to form salts is referred a base.

Properties of bases

• React with metals to form hydrogen gas.

React with non-metal oxide to farm salt and water.

Types of Bases

Strong Base

E.g NaOH, KOH, etc. 

Weak Base

E.g. NH₄OH, Al(OH)₃, Cu(OH)₂ etc.

Uses of Bases

1. Calcium hydroxide is used to manufacture Bleaching powder.
2. Sodium carbonate is used as washing soda and for softening hard water.
3. Sodium hydrogen carbonate is used as a baking soda in cooking food, making baking powder, as an antacid to cure indigestion and in soda-acid fire extinguishers.
4. Sodium hydroxide is used as a cleansing agent, in the soap and textile industries.

Salt

Acids and bases react with each other to form salts.

e.g: Sodium Chloride, Barium sulfate, Sodium nitrate.

Examples:

      )

Limitation of the Perception-Based Definition of Acids, Bases, and Salt

They are not scientific. 

There are many examples of acids and bases that cannot be classified under the old concepts.

We know that even gasses like ammonia acts as a base in water and Carbon dioxide acts as an acid in water.

The slippery or soapy powder boric acid used in carom board is not a base but an acid.

It does not explain the ionic equilibrium and conduction of electric current

New theories have been proposed based on scientific analysis to classify an acid or base or salt, like-

Arrhenius Theory, Lowry Bronsted Theory, Lewis Concept

Practice Problems

Q1. Which of the following is a mineral acid?

1. 
2. 
3. 
4. All are mineral acids

Answer: (B)

All inorganic acids are known as mineral acids. Hence in options (A) and (C), these are organic acids and in option (B), it is an inorganic acid. Hence, the correct option is (B)

Q2. Mineral acids are also known as

A.    Strong Acid

B.    Strong Base

C.    Weak Acid

D.   Weak Base

Answer : (A)

The acid prepared from the minerals of the earth are called mineral acids and are also known as Strong acids.

 Hence, the correct option is (A)

Q3.   Organic acids are also known as

A.   Strong Acid

B.   Strong Base

C.   Weak Acid

D.   Weak Base 

Answer : (C)

The acidic substances present in plants and animals are organic acids and are also known as Weak acids.  Hence, the correct option is (C)

Q4.   The acid reacts with active metals to liberate ……...

A.            Hydrogen gas

B.            Sulfur dioxide

C.            Carbon dioxide

D.           None of these

Answer : (A)

Acid reaction with active metals liberate hydrogen gas.

Frequently Asked Questions – FAQs

Q1. Guess the colour of litmus in a solution of sodium carbonate? 

Sodium carbonate is a salt of a strong base and a weak acid. So, its aqueous solution will be basic in nature. A red litmus paper turns blue in basic solutions, while a blue litmus paper retains its blue colour. So a red litmus paper changes to blue colour in basic sodium carbonate solution.. 

Q2. When sodium hydrogen carbonate is heated, what products formed during the reaction?

On heating sodium hydrogen carbonate (NaHCO3). It decomposes to form sodium carbonate (Na2CO3), water (H2O), and carbon dioxide.

Q3. ENO is taken to cure acidity. Can you suggest the nature of the ingredients present in it?

If we want to reduce the acid content in our body, we have to take some quantity of base to neutralize it.   ENO contains basic salts like sodium carbonate and bicarbonate. The sour taste of ENO is due to the presence of a small quantity of citric acid which is present in minute amounts.

Q4. What is Universal Indicator?

A pH indicator that shows different colours for different pH ranges to identify them as an acid or a base is called a universal indicator. Such indicator contains several compounds active at different pH ranges without much interference with each other. Phenolphthalein, sodium hydroxide, methyl orange, and thymol blue are some of the common ingredients in universal indicators.