CBSE Class 11 Chemistry Revision Notes Chapter 9

Class 11 Chemistry Revision Notes for Chapter 9 – Hydrogen

Students will learn about the isotopes, properties, reactions, and location of hydrogen in the periodic table and other significant topics by studying Class 11 Chapter 9 Hydrogen. Extramarks provides Chemistry Class 11 Chapter 9 Notes for students to help them become familiar with and clearly understand these concepts. Students in Class 11 can use the revision notes as a helpful study resource because they are readily available and easy to access.

At Extramarks, we understand the importance of revision notes and we take our role seriously to provide the best resource to the students and help them get excellent grades. Students may sign up at Extramarks’ website and app to find all answers that are easily accessible. Students need not look elsewhere for further assistance because it has all the answers students might need to boost their academic scores. 


Revision Notes for Class 11 Chemistry Chapter 9 – Hydrogen – Free Download

Class 11 Chemistry Revision Notes for Chapter 9 – Hydrogen

About Hydrogen Revision Notes

Hydrogen is the atom with the fewest electron and is also known as the lightest one. It is known to have the simplest atomic structure compared to all elements in nature. It merely contains one proton and one electron in its atomic structure. However, it is known as dihydrogen and occurs as a diatomic (H2) molecule in its elemental state. More compounds than any other element are formed by it. The loss of this electron produces the proton, an elementary particle. Additionally, hydrogen only has one character like this. 

The hydrogen atom has three isotopes: deuterium, protium, and tritium. Out of these three isotopes, only tritium is radioactive. Hydrogen also resembles halogens and alkali metals. The most notable fact is that it has held a separate position in the periodic table because of its unique properties. Furthermore, it is not found in its free form in the Earth’s atmosphere.

On an industrial scale, petrochemicals are used to produce dihydrogen through a water-gas shift reaction. The dihydrogen H-H bond has the highest dissociation enthalpy of any bond between two atoms in any element. This property is also used by a hydrogen torch, which is ideal for welding. In addition, the reducing reaction of dihydrogen produces methanol, hydrogen halides, ammonia, water, and other substances. The other significant compound created by the electrolytic enrichment of ordinary water is heavy water.


Subsections Covered within Chapter 9 – Hydrogen

Let’s take a closer look at the subsections of Chapter 9 regarding hydrogen.

Hydrogen Position in the Periodic Table– This topic focuses on the periodic table’s position of hydrogen. It is the first element in the periodic table.

Hydrides- Except for noble gases, hydrogen can combine with a wide range of other elements to form binary compounds known as hydrides. This topic discusses the different types of hydrides.

Under specific reaction circumstances, dihydrogen combines with nearly all elements— besides noble gases—to form binary compounds known as hydrides. If an element has “E” as its symbol, hydride can be written as EHx (for example, MgH2) or EmHn (e.g., B2H6).

The hydrides are classified into the following categories :

(i) Ionic or saline or salt-like hydrides

(ii) Covalent or molecular hydrides

(iii) Metallic or non-stoichiometric hydrides

Dihydrogen– Given that dihydrogen makes up roughly 70% of the universe’s total mass, dihydrogen is the most prevalent element in the universe. However, 0.15 per cent of the Earth’s atmosphere contains it. Hydrogen exists in its free form in volcanic gases, which together make up 15.4% of the earth’s crust and oceans. However, it can also be found in the proteins and carbohydrates of plants and animals, as well as in their tissues. Mineral resources like coal and petroleum also contain hydrogen. This topic goes into great detail about dihydrogen.

Preparation and Properties of Dihydrogen– This topic provides an overview of dihydrogen preparation and dihydrogen’s properties.  Dihydrogen can be produced from metals and metal hydrides in a variety of ways.

The methods explained are the following :

  1. Laboratory Preparation of Dihydrogen
  2. Commercial Production of Dihydrogen

Dihydrogen is a combustible, colourless, flavourless, and odourless gas. It is insoluble in water and lighter than air. Dihydrogen’s chemical behaviour, and that of any molecule for that matter, is largely governed by bond dissociation enthalpy.

Uses of Dihydrogen – This section lists the various uses of Dihydrogen. It highlights the significance of Dihydrogen. 

There are numerous uses such as :

  • It is frequently employed in the production of metal hydrides.
  • It is employed in the production of the extremely useful chemical hydrogen chloride.
  • It is used to convert heavy metal oxides to metals in metallurgical processes.

Water– Water, which is an oxide of hydrogen, is a crucial part of every living thing. About 95 per cent of plants and 65 per cent of humans are made up of water, which is a necessary and readily available chemical for life. Given that water makes up almost three-fourths of the earth’s surface and has a strong tendency to dissolve a variety of other substances, it is an essential component. Further, this topic discusses the structure of water as well as its physical and chemical characteristics.

Heavy Water and Hydrogen Economy- This subsection addresses the uses of heavy water, its safety for human consumption, and the hydrogen economy. For the study of reaction mechanisms, Heavy water is widely used as a moderator in nuclear reactors and in exchange reactions. It can be created either through exhaustive electrolysis of water or as a byproduct in some fertiliser manufacturing processes.

Hydrogen Peroxide- This specific topic provides information on hydrogen peroxide’s composition, manufacturing process, and applications.


Importance of Class 11 Chemistry Hydrogen

Hydrogen, which only has one electron, is the lightest atom in the universe. It was first discovered in the year 1766 by Henry Cavendish. Hydrogen has three stable isotopes: protium, deuterium, and tritium. Among these three, tritium is the radioactive isotope. One of the elements that are most prevalent in the universe is hydrogen. Despite having similarities to halogen and alkali metals, it is distinct from them in the periodic table and has their own position.

Due to its suitability for real-time applications and usage in daily life, hydrogen is a key topic in Class 11 Chemistry. By learning about this subject, students can better prepare for their final exams and learn more about the subject. Students can find accurate Chemistry Chapter 9 Class 11 Notes here at Extramarks, which will help them understand the chapter better and also make it easier for them to respond to tough questions. It is a thoroughly researched material made as per the CBSE examination guidelines. When students study from it, they will get an edge over their peers. 

FAQs (Frequently Asked Questions)

1. Why Choose Extramarks for Class 11 Chemistry Chapter 9 Notes?

The benefits of choosing Extramarks as a learning platform for Class 11 Chemistry Chapter 9 Notes are listed below.

  • Before taking the final exam, students can go through the Chapter 9 Chemistry Class 11 Notes given to revise authentic, accurate and reliable notes on every topic. These notes are prepared by the subject matter experts as per the latest CBSE syllabus and NCERT guidelines and curriculum.
  • Chapter 9 Chemistry Class 11 Notes can be used by students for quick revision as well. They are complete in every way for students to learn and grasp with better understanding and score well. No wonder students have complete faith and trust in Extramarks 
  • As they read through these notes, students will be able to understand every concept and answer any question easily. This encourages the students to master the topic and increases their confidence in achieving a higher grade.

2. Name a few applications for H2.

Let’s examine the following list of applications for the hydrogen compound.

  • Due to its high calorific value, it is utilised as rocket fuel.
  • Oxy hydrogen flame is employed in welding.
  • It also helps with the synthesis of HNO3, nitric acid, NH3, ammonia, HCl, and other substances. 
  • It helps with the production of vanaspati ghee.
  • It functions only as a reducing agent.

3. Explain the physical properties of Hydrogen.

Following are some of hydrogen’s physical characteristics:

  • Hydrogen gas is tasteless, odourless, and colourless. 
  • It is lighter than air because of its vapour density of 1.
  • It is non-toxic. 
  • The compound is barely soluble in water. 

4. Describe how hard water and soft water differ.

Hard water:

  • Mineral content in hard water is high.
  • When using this water and soap, no lather is produced.
  • Ions of calcium and magnesium are present.
  • Dry skin and hair result from using this water.

For example, groundwater.

Soft water:

  • There are not many elements in this water.
  • When soap is used with this water, the lather is produced.
  • In this water, sodium ions are present.
  • Skin and hair become softer by using this water.

For example, rainwater.