Muskan Shafi Education Content Expert
Education Content Expert
Acids and Bases are chemicals that lead to the formation of salt and water on interacting with each other. Acids and Bases play an integral role in Chemistry and are readily available in daily life.
- Acids are substances that donate a hydrogen ion (H+) to another substance in an aqueous solution.
- Bases are those substances that accept the proton and donate the electron.
- Acids have a pH of less than 7 and Bases have a pH of more than 7.
- Acids turn blue litmus red while Bases turn red litmus blue.
Difference between Acid and Base helps in differentiating several compounds in chemistry and is very crucial in chemical reactions.
Read More: Importance of pH in Everyday Life
Key Terms: Acids, Bases, Hydrogen, Proton, Litmus Paper, Salts, Electron, Organic Acids, Ammonia, Acid Catalysis
What are Acids?
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Acids are compounds that donate a Hydrogen Ion (H+) to another compound which is usually called a base. They are mostly obtained from natural sources.
- A molecule or compound that contributes a proton or accepts an electron pair is called an Acid.
- Acids are sour in taste and turn blue litmus paper red.
- They react with bases to form salts.
- They also facilitate chemical processes and reactions (Acid Catalysis).
- Acids have a pH of less than 7.0 and are usually sticky in nature.
- They give a burning sensation on contact with the skin.
- Examples: Hydrochloric Acid, Nitric Acid, Citric Acid, etc.
What are Acids?
Read More: NCERT Solutions for Class 10 Science Acids, Bases and Salts
Properties of Acids
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Some important properties of Acids are listed below:
- Acidic aqueous solutions are electrolytes, i.e. they conduct electricity.
- Some acids are powerful electrolytes because they totally ionize in water and produce a large number of ions.
- When dissolved in water, other acids are weak electrolytes that largely exist in a non-ionized state.
- Acids have a sour taste and are found in lemons, vinegar, and sour candies.
- Acids change the color of things, and litmus and phenolphthalein are two typical indicators.
- In the presence of an acid, blue litmus turns red, whereas phenolphthalein turns colorless.
- Acids produce hydrogen gas when they react with active metals.
- Acids react with bases to form Salts and Hydrogen.
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Types of Acids
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Acids can be categorized into two major types namely
- Organic Acids
- Inorganic Acids
Inorganic acids are also referred to as Mineral Acids.
Organic Acids
- Organic acids are caustic and poisonous substances.
- Corrosivity is a type of toxicity that occurs when an acid comes into contact with the tissues.
- Organic acids and their derivatives are used to make a wide variety of products.
- They're used in almost every kind of chemical product as they have a wide range of chemical structures.
- Acetic Acid and Oxalic Acid are organic acids.
Inorganic Acids
- Inorganic acids are basically known as Mineral Acids.
- It is possible for the anhydrous state to be gaseous or solid.
- An inorganic anhydride is a metalloid oxide that can react with water to produce an inorganic acid.
- Sulphuric Acid, Phosphoric Acid, and Nitric Acid are some inorganic acids.
Read More: Acids Bases and Salt Revision Notes
Strong and Weak Acids
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Acids can be classified into Strong and Weak Acids on the basis of the ion dissociation in water. Strong acids dissociate ions completely in the water while weak acids partly dissociate into ions in water.
Strong Acids
Strong Acids are defined as those acids that completely dissociate ions in water. Examples of Strong Acids are as follows:
- Hydrochloric Acid (HCL)
- Hydrobromic Acid (HBr)
- Nitric Acid (HNO3)
- Hydroiodic Acid (HI)
- Chloric Acid (HClO3)
- Perchloric Acid (HClO4)
- Sulphuric Acid (H2SO4)
Weak Acids
Weak Acids are those acids that partly dissociate ions in water. All acids except the strong acids are considered to be weak acids. Examples of Weak Acids are as follows:
- Formic Acid (HCOOH)
- Acetic Acid (CH3COOH)
- Benzoic Acid (C6H5COOH)
- Oxalic Acid (C2H2O4)
- Hydrofluoric Acid (HF)
Strong and Weak Acids
What are Bases?
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Bases are substances that accept the proton and donate an electron, i.e. bases are H+ acceptors.
- They react with an acid to form salt and water.
- They have a bitter taste and turn red litmus paper blue.
- The pH value of bases is always greater than 7.
- Bases that are soluble in nature are known as Alkalis.
- Examples: Sodium Bicarbonate, Calcium Carbonate, Ammonia, etc.
What are Bases?
Properties of Bases
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Some important properties of Bases are as follows:
- Electrolytes are aqueous solutions of bases.
- Bases, like acids, can be either strong or weak.
- Bases have a bitter flavor and are less commonly found in foods than acids.
- Many bases, such as soaps, are slippery to the touch.
- In the presence of a base, red litmus turns blue, while phenolphthalein turns pink.
- Bases and acids combine to form salt and water.
Read More: Acids Bases and Salt Important Questions
Types of Bases
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There are different types of bases which are as follows:
- Strong Bases: They totally dissociate into their ions in water or a substance that can take a proton (H+) from a weak acid.
- Weak Bases: They completely dissociate in water. One example of a base and its conjugate acid is an aqueous solution.
- Neutral Bases: These bases form a bond with a neutral acid.
- Super Bases: They are made up of an alkali metal and its conjugate acid. They are even better than a strong base.
- Solid Bases: They may be used in anion exchange resins or in reactions with gaseous acids as a solid base.
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| Related Topics | ||
|---|---|---|
| Difference between Alkali and Base | Definition and Examples of Bases in Everyday Life | Examples of Weak Acids |
| Neutralization | Types of Solutions | pH Formula |
Difference Between Acid and Base
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Acids and Bases are two different types of chemical substances and vary from each other in several aspects. The difference between Acid and Base is as follows:
| Basis | Acids | Bases |
|---|---|---|
| Definition | Acids are chemical substances that, when dissolved in water, generate a solution with more hydrogen ion activity than purified water. | Bases are aqueous substances that donate electrons, accept protons, or release hydroxide (OH-) ions. |
| pH Value | Acids have a pH of less than 7.0. | Bases have a pH of greater than 7.0. |
| Litmus Paper | Acids turn blue litmus paper into red. | Bases turn red litmus paper to blue. |
| Phenolphthalein | Phenolphthalein remains colorless on exposure to Acids | When bases are dissolved, the Phenolphthalein solution turns pink. |
| Physical Characteristics | Acids can be solid, liquid, or gaseous. They have a sour taste. | Bases are slippery and solid in nature (except for ammonia, which is gaseous). They have a bitter taste. |
| Disassociation | When acids are combined with water, hydrogen ions (H+) are released. | When bases are combined with water, hydroxide ions (OH-) are released. |
| Examples | Acetic Acid, Sulfuric Acid, Hydrochloric Acid, Salicylic Acid, etc. | Sodium Hydroxide, Ammonia, Calcium Carbonate, Potassium Oxide, etc. |
Things to Remember
- Acids and Bases are chemical substances that form Salts on reaction with each other.
- Acids are ionic compounds that produce positive hydrogen ions (H+) when dissolved in water.
- Bases are chemical substances that donate electrons and accept protons (H+ Ions).
- Acids are sour in taste while bases are bitter in taste.
- Acids release hydrogen ions (H+) while Bases release hydroxide ions (OH-) on reaction with water.
- Bases turn red litmus blue while Acids turn blue litmus red.
- Acids are divided into Organic Acids and Inorganic (Mineral) Acids.
- They can also be classified into Strong Acids and Weak Acids.
- Bases are divided into various types such as Strong Bases, Weak Bases, Neutral Bases, etc.
Sample Questions
Ques. List the properties of Acids. (3 Marks)
Ans. The properties of Acids are as follows:
- Acids are sour in taste and corrosive in nature.
- They are considered to be good conductors of electricity.
- The pH value of acids is always less than 7.
- Acids produce hydrogen gas when reacted with metals.
Ques. Differentiate between Acids and Bases. (5 Marks)
Ans. The major differences between Acids and Bases are listed below:
| Acids | Bases |
|---|---|
| Acids release hydrogen ions when dissolved in water. | Bases release hydroxide ions when dissolved in water. |
| They turn blue litmus paper into red. | They turn red litmus paper into blue. |
| Acids have a sour taste. | Bases have a bitter taste and are soapy to the touch. |
| pH value of Acids ranges from 1 to 7. | pH value of Bases ranges from 7 to 14. |
| Examples: Hydrochloric Acid (HCl), Sulphuric Acid (H2SO4), etc. | Examples: Sodium Hydroxide (NaOH), Potassium Hydroxide (KOH), etc. |
Ques. What is pH? (3 Marks)
Ans. pH of a substance indicates the alkalinity or acidity present in a solution. The values on a pH scale range from 0 to 14.
A substance can be classified as a neutral, acidic, or basic solution on the basis of the given criteria:
- pH < 7: Acidic
- pH> 7: Basic
- pH = 7: Neutral
Ques. Who donates and accepts protons between Acids and Bases? (2 Marks)
Ans. Acid is a chemical that donates protons or takes a pair of valence electrons to create a bond. Bases have the ability to accept or absorb protons or contribute a pair of valence electrons in order to create a bond.
Ques. Mention the properties of Bases. (3 Marks)
Ans. The properties of Bases are as follows:
- Bases have a soapy or slippery texture when touched.
- Hydroxide ions (OH– ions) are released when bases are dissolved in water.
- Bases act as good conductors of electricity in their aqueous solutions.
- pH value of bases is always greater than 7.
- Bases taste bitter and turn red litmus paper blue.
Ques. Is pure water Acidic or Alkaline? (3 Marks)
Ans. Water (H2O) is neither acidic nor basic. Pure water has a pH of 7 which means it is neutral. Pure water is neutral because the quantity of positive hydrogen ions produced equals the number of negative hydrogen ions produced.
Although the pH of pure water is 7, natural water or drinking water exhibit a pH range as they contain dissolved minerals and gases. Surface waters have a pH range from 6.5 to 8.5, while groundwater ranges from pH 6 to 8.5.
Ques. What are Alkalis? Are all bases alkalis? (3 Marks)
Ans. Bases are chemical compounds that can accept hydrogen ions. Bases are sometimes referred to as ‘Alkalis’, however, not all bases are alkalis as all bases are not soluble in water. Alkalis are defined as bases that dissolve in water to generate the hydroxyl ion (OH-). Water-soluble alkalis, such as barium carbonate, usually only become soluble in water after reacting with an acidic solution that contains water.
Ques. List some important Bases and their uses. (3 Marks)
Ans. Some important bases with their chemical formula and uses are as follows:
- Sodium Hydroxide (NaOH) is a common ingredient in soaps and detergents, as well as oven and drain cleaners.
- Calcium Hydroxide (Ca(OH)2) is a chemical compound that is used to make cement and lime water. In addition, it is used to neutralize acidic soil.
- Ammonia (NH3) is a chemical compound that is used to make a variety of pharmaceutical items as well as a variety of commercial cleaning solutions. It is also used to make fertilizers.
Ques. (i) Dry pellets of a base ‘X’ when kept in open absorb moisture and turn sticky. The compound is also formed by chlor-alkali process. Write the chemical name and formula of X. Describe chlor-alkali process with a balanced chemical equation. Name the type of reaction that occurs when X is treated with dilute hydrochloric acid. Write the chemical equation.
(ii) While diluting an acid, why is it recommended that the acid should be added to water and not water to the acid? (5 Marks) [CBSE 2012]
Ans. (i) The substance ‘X’ is Sodium Hydroxide (NaOH).
When sodium chloride solution (brine solution) is electrolyzed, sodium hydroxide solution is formed. H2 and Cl2 gases are liberated. This is known as the chlor-alkali process.
2NaCl + 2H2O → 2NaOH + H2 + Cl2
When X (NaOH) is treated with dilute hydrochloric acid, the following reaction occurs:
NaOH + HCl → NaCl + H2O
The above reaction is a Neutralization Reaction.
(ii) It is because the process is highly exothermic. If water is added to acid, the bottle of acid will break and the amount of heat released can cause a lot of damage.
Ques. Define Base. List its examples. (3 Marks)
Ans. Bases are substances that react with hydrogen ions and can neutralize acids. They form water and salts by reacting with acids. Bases include metal oxides, hydroxides, and carbonates.
Examples of Bases are:
- Sodium Hydroxide
- Calcium Carbonate
- Potassium Oxide
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