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Hydrogen Class 11 Notes CBSE Chemistry Chapter 9 (Free PDF Download)

Last updated date: 17th May 2024
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Revision Notes for CBSE Class 11 Chemistry Chapter 9 (Hydrogen) - Free PDF Download

Class 11, chapter 9, deals with the topic of Hydrogen is basically structured in a manner to help the students to know everything about the element in full detail. By studying the Hydrogen chapter, students will know about its isotopes, properties, reactions, the position of hydrogen in the periodic table, and the other important topics. Therefore, to help the students become familiar with these topics and understand them clearly, CBSE revision notes for Chemistry Class 11 Chapter 9, hydrogen is provided here, at Vedantu. Students can download the revision notes seemingly in the form of a PDF file and use them as an effective reference tool to complete their revisions in time, prepare well, and fetch higher grades in the final exams.

Download CBSE Class 11 Chemistry Revision Notes 2024-25 PDF

Also, check CBSE Class 11 Chemistry revision notes for other chapters:

Hydrogen Chapter Related Important Study Materials
It is a curated compilation of relevant online resources that complement and expand upon the content covered in a specific chapter. Explore these links to access additional readings, explanatory videos, practice exercises, and other valuable materials that enhance your understanding of the chapter's subject matter.

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Hydrogen Class 11 Notes Chemistry - Basic Subjective Questions

Section – A (1 Mark Questions)

1. Which isotope of hydrogen

(i) does not contain neutron?

(ii) is radioactive?

Ans. (i) Protium

(ii) Tritium

2. Name the isotopes of hydrogen.  

Ans. Hydrogen has three isotopes:

Protium, $^1_1\text{H}$

deuterium, $^2_1\text{H}$

tritium, $^3_1\text{H}$

3. Give the laboratory method of preparation of hydrogen.  

Ans. Hydrogen is usually prepared by the reaction of granulated zinc with dilute hydrochloric acid


4. Give the commercial method of preparation of dihydrogen.  

Ans. Electrolysis of acidified water using platinum electrodes give hydrogen.

$2\text{H}_2\text{O}(\text{l})\xrightarrow[\text{Trace of acid/base}(\text{H}^+/\text{OH}^-)]{\text{Electrolysis}}2\text{H}_2(\text{g})+\text{O}_2(\text{g})$

5. Why is dihydrogen gas not preferred in balloons?  

Ans. Dihydrogen is the lightest gas and should have been used in balloons. But it is not preferred due to its highly combustible nature.

6. How is ammonia prepared using dihydrogen?  

Ans. With dinitrogen it forms ammonia.



This is the method for the manufacture of ammonia by the Haber process.

7. Give an example of each of an ionic hydride and a covalent hydride. 

Ans. Ionic hydride: LiH, NaH. 

Covalent hydride : CH4, NH3 and H2O.

8. What happens when water is added to calcium hydride?  

Ans. Calcium hydroxide is formed $\underset{(\text{calcium hydride})}{\text{CaH}_2}+2\text{H}_2\text{O}\rightarrow\underset{\text{calcium hydroxide}}{\text{CaOH}_2}+2\text{H}_2$

9. What is Calgon?  

Ans. Sodium hexametaphosphate (Na6P6O18) is commercially called Calgon.

10. How is heavy water obtained from ordinary water?

Ans. Heavy water is obtained from ordinary water by repeated electrolysis in the presence of 3% NaOH.

Section – B (2 Marks Questions)

11. Define hard water. What makes water hard? Does hard water give lather with soap ?  

Ans. Water which does not produce lather with soap solution readily is called hard water. E.g. Hand pump water, river water, sea water etc. Presence of calcium and magnesium salts in the form of hydrogen carbonate, chloride and sulphate in water makes water hard. It does not give lather with soap.

12. Why is ice less dense then water and what kind of attractive forces must be overcome to melt ice?  

Ans. The structure of ice is an open structure having a number of vacant spaces. Therefore, the density of ice is less than water. When ice melts the hydrogen bonds are broken and the water molecules go in between the vacant spaces. As a result, the structure of liquid water is less open than structure of ice. Thus, ice is less dense than water.

13. Why is water an excellent solvent for ionic or polar substances?  

Ans. Water is a polar solvent with a high dielectric constant. Due to high dielectric constant of water the force of attraction between cation and added substance gets weakened. Thus water molecules are able to remove ions from the lattice site using ion dipole forces easily.

14. What do you understand by : 

(i)water – gas shift reaction

(ii) syn-gas?  

Ans. (i)The production of dihydrogen can be increased by reacting carbon monoxide of syn gas mixtures with steam in the presence of iron chromate as catalyst.


This is called water gas – shift reaction.Carbon dioxide is removed by scrubbing with sodium arsenite solution.

(ii) The mixture of CO and H2 is called water gas.As this mixture of CO and H2 is used for the synthesis of methanol and a number of hydrocarbons it is also called synthesis gas or ‘syngas’

15. Write two uses of interstitial hydrides.  

Ans. Two important uses of  interstitial hydrides are :

(i) For storing H2 gas

(ii) As catalysts for hydrogenation reactions.

16. What happens when sodium hydride reacts with water?

Ans. Saline hydride (sodium hydride) react violently with water producing dihydrogen gas

NaH(s) + H2O(aq) → NaOH(aq) + H2(g)

17. Show with reaction the amphoteric nature of water.  

Ans. Water acts as an acid with NH3 and base with H2S



18. Distinguish between:

Temporary hardness & permanent hardness of the water.


ans 18

19. Give the main characteristics of isotopes.  

Ans. Since, the isotopes have the same electronic configuration, they have almost the same chemical properties. The only difference is in their rates of reactions, mainly due to their different enthalpy of bond dissociation. However, in physical property these isotopes differ considerably due to their large mass differences.

20. Classify the following as covalent, ionic polymer or interstitial hydrides:

(i) BeH2

(ii) CaH2

(iii) GeH4

(iv) TiH2


ans 20

PDF Summary - Class 11 Chemistry Hydrogen Notes (Chapter 6)

About Hydrogen Revision Notes

Firstly, we can say that hydrogen is the lightest atom, which has only one electron. Further, the loss of this electron results in an elementary particle, which is the proton. Furthermore, this is a unique characteristic property of hydrogen. Moreover, hydrogen has three isotopes, which are called deuterium, protium, and tritium. Among all these three isotopes, only the tritium is radioactive. On the other side, it resembles both halogens and alkali metals. Most noteworthy is that it has occupied a separate position in the periodic table because of its unique properties. Also, it cannot be found in the earth’s atmosphere, in its free state.

On the industrial scale, the dihydrogen is prepared by the water-gas shift reaction from the petrochemicals. Furthermore, the dissociation enthalpy of the H-H bond of dihydrogen is the highest for a single bond between the two atoms of any element. Moreover, this property is used in a hydrogen torch, which can be ideal for welding. Besides, the reducing reaction of dihydrogen leads to the formation of methanol, hydrogen halides, ammonia, water, and more. In addition, the heavy water is the other important compound that is formed by the electrolytic enrichment of normal water.

Sub-topics Covered Under Hydrogen

Let us look at some of the sub-topics that fall under the Hydrogen chapter.

  • Hydrogen Position in the Periodic Table - This topic highlights hydrogen and its respective position in the periodic table.

  • Hydrides - This topic describes the hydrides and their various types.

  • Dihydrogen - This topic teaches about the dihydrogen in detail.

  • Preparation and Properties of Dihydrogen - This topic tells the overview of the preparation of dihydrogen and its properties as well.

  • Water - This topic tells about water and its physical, chemical properties, along with its structure.

  • Heavy Water and Hydrogen Economy - This topic covers heavy water, its uses, whether it is safe to consume, and the hydrogen economy.

  • Hydrogen Peroxide - This particular topic defines hydrogen peroxide, its preparation method, its structure, and its uses.

Importance of Class 11 Chemistry Hydrogen

Hydrogen is also an important topic in Chemistry. It matches to the realtime applications and uses in our daily lives. By studying this topic, students can get a good score in their final examinations and know about its real uses and applications and how to use it when necessary for realtime. The revision notes provided here at Vedantu help the students get a clear understanding of the topic and help them answer the questions given in the exams.

Why Choose Vedantu?

Students, by choosing their learning platform, as Vedantu, will be benefitted as given below.

  • They can clear their doubts about the topic, Hydrogen, before going for the final examination.

  • It can be achieved by referring to the revision notes at least more than once.

  • While going through this revision notes, students will remember the importance of the subject and also from the examination point of view.

  • They can download the revision notes and keep it with them and can revise it just a day before the exam or before going to attend the exam.

  • Using keywords such as Class 11 Chemistry Chapter 9 Hydrogen PDF, Class 11 Chapter 9 Revision Notes Hydrogen PDF, and more related.

Position of Hydrogen in the Periodic Table

Let us get to know the details of hydrogen about its position in the periodic table.

  • It is the lightest element which is having the atomic number 1.

  • It is also used as a Dihydrogen.

  • It resembles both halogens and alkali metals, and therefore, its respective position is anomalous.

  • In the modern periodic table, it is separately located.

Advantages for Using a Revision Notes

Let us look at aome some advantages of using Revisoin Notes.

Increase Attention Span

Considering learning, Study Notes or Revision notes promote retention. While learning is an imperative tutoring part, retention is an essential end goal. Preparing a revision notes promotes positive memory and the ability to retain information because the mind becomes active in studying. Not only the students do understand things better while writing in their own words with their handwriting, but they can also retain it for a longer time.

FAQs on Hydrogen Class 11 Notes CBSE Chemistry Chapter 9 (Free PDF Download)

1. List out some uses of H2?

Let us look at the uses of the hydrogen compound, as listed below.

  • It is used as a rocket fuel due to its high calorific value.

  • Oxy Hydrogen Flame is used for welding purposes.

  • It also helps in the synthesis of HNO3 (nitric acid), NH3 (ammonia), HCl (hydrochloric acid), and more.

  • It helps in the synthesis process of the vanaspati ghee.

  • It is completely a reducing agent.

2. Explain the physical properties of Hydrogen?

Some of the physical properties of hydrogen can be given as:

  • Hydrogen is colorless, tasteless, and odorless

  • It has a vapor density of 1, which is lighter than air

  • It is also non - poisonous

  • The solubility of the compound in H2O is very low

3. List out some important points on the Revision Notes?

  • Manage their time effectively and efficiently

  • Incorporate all the topics and subtopics that fall under the Hydrogen before going to the exams

  • Plan the timetable in terms of preparation according to the topic count, size of the topics, and more related

4. Where can I download the latest or previous year’s papers of my academic stuff?

You can download the question papers, revision notes, last 5 years papers, and other related information concerning the academics from India’s largest online learning platform, Vedantu. It is also quite easy to download the required papers from the site, simply using the search option available on the website.

Students can also download the same files from the respective official websites of the state board.

5. What topics does Chapter 9 of Class 11 Chemistry consist of?

The topics that Chapter 9 of Class 11 Chemistry consists of are:

  • Hydrogen having a position in the Periodic Table. 

  • The Dihydrogen

  • Preparation of Dihydrogen

  • Characteristics of Dihydrogen

  • Hydrides

  • Water and its Forms and Structure

  • Hydrogen Peroxide

  • Heavy Water

  • Use of Dihydrogen as a Fuel

In this chapter, you will learn about the element “Hydrogen” including its properties, isotopes, position, reactions, etc. This chapter is theoretical so students can easily prepare this chapter for their examination.

6. How can students prepare Chapter 9 for their Class 11 Chemistry examination?

The given study plan can help students to prepare Chapter 9 for their Class 11 Chemistry exam:

  • Study the Chemistry NCERT book thoroughly to understand the chapter.

  • Prepare the notes of the chapter so that you can remember the important points.

  • Solve NCERT questions of this chapter to get the hint about the questions asked in the exam.

  • Work out on various sample papers to comprehend the concepts easily.

  • Go through different guidebooks or reference books for more information about the chapter and to clarify your doubts.

 The study material for students is available on the Vedantu website and Vedantu app at free of cost.

7. Write the differences between hard water and soft water.

(a) Hard Water:

  • Hard water is abundant in minerals.

  • No formation of lather when this water is used with soap.

  • It contains calcium and magnesium ions.

  • Using this water, skin and hair becomes dry.

  • Example –groundwater

(b) Soft Water:

  • This water includes only a few elements.

  • Lather forms when soap is used with this water.

  • There are sodium ions in this water.

  • By utilizing this water, skin and hair becomes soft.

  • Example – rainwater

8. Why is water regarded as a good solvent for polar or ionic substances?

The molecules of water are highly polar in nature. When ionic substances are mixed in water then a large amount of hydration energy is released. This energy is more than that of the energy required to break the molecules of water. Therefore, high hydration energy results in the solvation of ionic substances in water.

In the case of polar substances, the energy released when water interacts with polar molecules is sufficient to break the water molecules or molecules of polar substances. This results in a mixture of water and polar substances.

9. List some characteristics and applications of dihydrogen.

Some characteristics and applications of dihydrogen are:

  • The dihydrogen exists as a gas at STO

  • -259.16 degrees Celsius is the melting of the dihydrogen.

  • 20.271 K is the boiling of the dihydrogen.

  • 0.904 kilojoules per mole is the latent heat of fusion of the dihydrogen.

  • In the manufacture of vanaspati fat, dihydrogen is used.

  • As it has high calorific value, it is used as rocket fuel.

  • In Haber's process, dihydrogen is used in the synthesis of ammonia.

  • Hydrogen chloride is made by using dihydrogen.