Careers360 Logo
Hydrogen Class 11th Notes - Free NCERT Class 11 Chemistry Chapter 9 Notes - Download PDF

Hydrogen Class 11th Notes - Free NCERT Class 11 Chemistry Chapter 9 Notes - Download PDF

Edited By Sumit Saini | Updated on Apr 26, 2022 01:13 PM IST

Class 11 Chemistry chapter 9 notes is focused on the topic of hydrogen and is organized in such a way that students can learn everything there is to know about the element in depth. Students will learn about hydrogen's isotopes, characteristics, reactions, periodic table position, and other essential topics by studying the CBSE Class 11 Chemistry chapter 9 notes. Hydrogen Class 11 notes are also constructed with the most recent NCERT Syllabus. Notes for class 11 chemistry chapter 9 contain all relevant information in the chapter Hydrogen in a concise manner. In addition to this, students can refer to the following links, and use them as a reference tool to finish their revisions on time, prepare effectively, and get better results on final exams.

Also, students can refer,

NCERT Class 11 Chemistry Chapter 9 Notes

NCERT Class 11 Chemistry Chapter 9 Notes: Topic 1

Position of Hydrogen in The Periodic Table

Hydrogen is found on Earth in the form of the H2 molecule (dihydrogen). It accounts for 10% of the universe's mass. Many compounds, such as carbohydrates and hydrocarbons, release hydrogen. It is the third most abundant element on the planet.

Hydrogen has similarities with alkali metals and halogens.

Similarities with alkali metals

  • The number of valence electrons is 1

  • Electropositive character

  • Oxidation state =+1

  • Powerful reducing agent.

Similarities with halogens

  • The ionization energy of hydrogen is remarkably similar to that of halogens.

  • Hydrogen and halogens exist as diatomic.

  • Covalent nature exists in many hydrogen and halogen compounds.

Despite the fact that hydrogen shares some similarities with alkali metals and halogens, it is different from them too. As a result, it has an unique behaviour and placed separately in the periodic table.

NCERT Class 11 Chemistry Chapter 9 Notes: Topic 2



Dihydrogen is the most abundant element in the universe(70%). It can be found in a variety of forms, including water, coal, animal, and vegetable materials. Hydrogen is an important component of all organic molecules.


Hydrogen has three isotopes

  1. Protium 1H1

JEE Main Highest Scoring Chapters & Topics
Just Study 40% Syllabus and Score upto 100%
Download EBook

1 electron, 1 proton and no neutrons

  1. Deuterium 1H2

1 electron, 1 proton and 1 neutron

  1. Tritium 1H3

1 electron, 1 proton and 2 neutrons. It is radioactive.

NCERT Class 11 Chemistry Chapter 9 Notes: Topic 3

Preparation of Dihydrogen

  • Laboratory preparation

It is made in laboratories by mixing powdered zinc with dilute hydrochloric acid.

Zn + 2H+ → Zn2+ + H2

Zn+2 NaOH → Na2ZnO2+H2

  • Electrolysis of water using platinum electrodes

2H2O Electrolysis→ 2H2+O2

  • Electrolysis of warm aqueous barium hydroxide solution between nickel electrodes.

  • Electrolysis of brine solution

At anode: 2Cl- → Cl2+2e-

At cathode: 2H2O + 2e- → H2 + 2OH-

  • Reaction of steam on hydrocarbons

CnH2n+1 + nH2O Ni,1270 Kn →CO+(2n+1)H2

Mixture of CO and H2 is called water gas or syngas. Production of sync gas from coal is called coal gasification.

C+H2ONi,1270 →KCO+H2

Water gas shift reaction

CO+H2O 673 K,Iron chromate→ CO2+H2

NCERT Class 11 Chemistry Chapter 9 Notes: Topic 4

Properties of Dihydrogen

Physical properties

  • Dihydrogen is a gas that is colourless, odourless, and tasteless.

  • It's a flammable gas.

  • It is insoluble in water.

  • It has a lower density than air

Chemical properties

  • Reaction with halogens

H2+X2 →2 HX

  • Reaction with dinitrogen

2H2+O2→ 2H2O

  • Reaction with metal

3H2+N2673 K,200 atm ,Fe →2NH3

  • Reactions with metal ions and metal oxides

H2+Pd2+ → Pd+2H+

yH2+MxOy →xM+y H2O

  • Reactions with organic compounds



NCERT Class 11 Chemistry Chapter 9 Notes: Topic 5


Dihydrogen reacts with a variety of elements to form binary compounds known as hydrides.

Ionic hydrides

They are formed when high-reactivity metals of group 1 and group 2 combine with hydrogen. Lithium, Beryllium, and Magnesium hydrides have the maximum covalent nature of all. They are crystalline in structure and have a high melting and boiling point. They have a higher density than metals. They conduct electricity and release H2 gas when melted.

Covalent hydrides

They're mostly made up of p-block elements and a few s-block elements, which have a smaller electronegativity difference than hydrogen. They are binary compounds with covalent bond.They are of 3 types

  • Electron deficient

They have fewer electrons than the octet. Eg:B2H6

  • Electron precise

They have a sufficient number of electrons. Eg:CH4

  • Electron rich

They have additional electrons than the octet. Eg: NH3

Molecular /non-stochiometric/interstitial hydrides

Molecular hydrides are produced when hydrogen reacts with the d and f elements in this reaction. Groups 6,7,8,9 and 3,4,5,10,11,12 do not produce hydrides, whereas group 3,4,5,10,11,12 can. This is referred to as the Hydride Gap (the inability of these groups to form hydrides is called Hydride gap). They don't have enough hydrogen. Non-stochiometric hydrides are another name for them. Interstitial spaces between these atoms are occupied by hydrogen.

NCERT Class 11 Chemistry Chapter 9 Notes: Topic 6


Water makes up roughly 65 percent of the human body, while it makes up nearly 95 percent of some plants.

Physical properties

  • Water makes up roughly 65 percent of the human body, while it makes up nearly 95 percent of some plants.

  • At 4°C, the maximum density of water is 1 gm cm-3

  • It is a tasteless, colourless liquid.

  • Even covalent substances like alcohol and carbohydrates dissolve in water due to hydrogen bonding with polar molecules.

Structure of water

It is a bent molecule in gas phase, with a HOH bond angle of 104.5° and an O—H bond length of 95.7 pm. It has polar nature.



Structure of ice

The crystalline form of water is ice. Ice crystallizes hexagonally at atmospheric pressure. It condenses to cubic shape at low temperatures. Ice is lighter than water and has a lower density. As a result, ice cubes float in water.

Chemical properties

  • Amphoteric nature

H2O+NH3 ↔ OH- + NH4+

H2O+H2S ↔ H3O+ + HS-

  • Oxidizing and reducing nature

2H2O+2Na → 2NaOH+H2

6CO2+12H2O → C6H12O6+6H2O+6O2

2F2+2H2O → 4H++ 4F-+O2

  • Hydrating tendency

P4H10+6H2O → 4H3PO4

SiCl4+2H2O → SiO2+4HCl

N3-+3H2O → NH3+3OH-

  • Hydrates formation

Coordinated water: [Cr(H2O)6]3+ 3Cl-

Interstitial water: BaCl2.2H2O

Hydrogen bonded water:[Cu(H2O)2+ SO42-.H2O

NCERT Class 11 Chemistry Chapter 8 Notes: Topic 7

Hardness of Water

The presence of calcium and magnesium (Ca2+ and Mg2+) salts in water causes this. The water containing these salts is called hard water. Magnesium bicarbonates, sulphates, chlorides, calcium bicarbonates, sulphates, and chlorides are the most common salts Calcium and magnesium salts in hard water react with soap to generate an insoluble precipitate known as scum. It sticks to the fabric.

2C17H35COONa+M2+ → (C17H35COO)2M ↓+2 Na

Temporary hardness

It is caused by the presence of calcium and magnesium bicarbonates in the water. It's called temporary since it's easy to get rid of by simply boiling hard water. It can be removed by

  • Boiling

Mg(HCO3)2 ∆→ Mg(OH)2↓+2CO2

Ca(HCO3)2 ∆→ Ca(CO)3↓+H2O+CO2

  • Clark’s method

Ca(HCO3)2+Ca(OH)2 → 2 Ca(CO)3↓+2H2O

Mg(HCO3)2+2Ca(OH)2 → 2 Ca(CO)3↓+Mg(OH)2↓+2H2O

Permanent hardness

It is caused by the presence of calcium and magnesium chlorides and sulphates.Chemical treatments can be used to remove permanent hardness from water.

  • Treatment with washing soda

MCl2+Na2CO3 MCO3↓+2NaCl

MSO4+Na2CO3 MCO3↓+2Na2 SO4

  • Calgon’s method

Na2P6O18 → 2Na++Na4P6O182-

M2++Na4P6O182- → [Na2MP6O18]2-+2Na+

  • Ion exchange method(Zeolite/permutit process)

2NaZ+M2+ MZ2+ 2Na+

MZ2+2NaCl → 2NaZ+MCl2


  • Synthetic resins method

Synthetic resin methods outperform ion exchange methods because they remove all forms of cations and anions, leaving only distilled water.

Cation exchange resin: It is made up of a massive hydrocarbon structure connected to fundamental groups. They are represented by the R-COOH or R-SO3H general formula. This R stands for large hydrocarbon. These resins have the ability to exchange H+ions with cations found in hard water.

Anion exchange resin: An ion exchange resin is made comprised of a large hydrocarbon matrix that is connected to basic groups such as OH-ions, commonly in the form of substituted ammonium hydroxides. They are denoted by the letters R-NH3OH, where R stands for large hydrocarbon framework. These resins may exchange hydroxide ions with anions found in hard water, such as chloride ions and sulphate ions.

NCERT Class 11 Chemistry Chapter 9 Notes: Topic 8

Hydrogen Peroxide (H2O2)


  • BaO2.8H2O+H2SO4 → BaSO4+H2O2+8H2O

  • 2HSO4- Electrolysis→ HO3SOOSO3 Hydrolysis→ 2HSO4-+2H++H2O2

  • 2-ethylanthraquinol O2→ H2O2

Physical properties

  • It is a clear liquid with no colour.

  • It is miscible in all quantities with water and produces the hydrate H2O2. H2O


H2O2 has a nonpolar structure.


Chemical properties

  • Oxidation reactions in acidic medium

2Fe2++2H++H2O2 → 2Fe3++2H2O

PbS+4H2O2 → PbSO4+4H2O

  • Oxidation reactions in basic medium

2Fe2++H2O2 → 2Fe3++2OH-

Mn2++H2O2 → Mn3++2OH-

  • Reduction reactions in acidic medium

2MnO4-+6H++5H2O2 → 2Mn2++8H2O+5O2

HOCl+H2O2 → H3O++Cl-+O2

  • Reduction reactions in basic medium

I2+H2O2+2OH- → 2I-+2H2O+O2

2MnO4-+3H2O2 2MnO2+3O2+2H2O+2OH-

NCERT Class 11 Chemistry Chapter 9 Notes: Topic 9

Heavy Water (D2O)

It is produced via electrolysis of water over a long period of time. It is employed in nuclear reactors as a moderator. It's used to investigate reaction mechanisms through exchange reactions. Heavy water is used for the preparation of other dueterium compounds.

CaC2+2D2O C2 →D2+Ca(OD)2

SO3+D2O → D2SO4

Al2C3+12D2O → 3CD4+4Al(OD)3

NCERT Class 11 Chemistry Chapter 9 Notes: Topic 10

Dihydrogen as a Fuel

The conveyance and storage of energy in the form of liquid or gaseous dihydrogen is the core premise of the hydrogen economy. The fact that energy is transmitted in the form of dihydrogen rather than electric power is an advantage. As a fuel, it has the following advantages: - It can be used in fuel cells to generate electricity. One of the key benefits of hydrogen combustion is that it produces very little pollution and does not emit any unburnt carbon particles in the form of smoke. The study shows that dihydrogen, both in gaseous and liquefied form, releases more energy when burned than other regularly used fuels. CNG is blended with 5% dihydrogen for use in four-wheeler vehicles.

Significance of NCERT Class 11 Chemistry Chapter 9 Notes

In Chemistry, hydrogen is a significant topic. It is appropriate for real-time applications and uses in our everyday life. Students can improve their final test scores by studying this Hydrogen Class 11 notes and learning about its real-world uses and applications, as well as how to employ it in real-time situations. Students can use the review Hydrogen Class 11 notes to gain a better understanding of the material and to answer the questions in the board exam as well as other competitive exams including NEET and JEE MAIN. Students can use Class 11 Chemistry chapter 9 notes pdf download for learning in offline mode.

NCERT Class 11 Notes Chapter-Wise

Subject Wise NCERT Exemplar Solutions

Subject Wise NCERT Solutions

Frequently Asked Question (FAQs)

1. 1 What are the physical properties of hydrogen mentioned in Hydrogen Class 11 notes?

Ans: Class 11 Chemistry chapter 9 notes mention physical properties of hydrogen. Hydrogen is a colourless, odourless, and tasteless gas. It’s vapour density is one, making it lighter than air. In addition, it is non-poisonous. Hydrogen has relatively poor solubility in water.

2. 2.What are the uses of hydrogen according to NCERT notes for Class 11 Chemistry chapter 9?

Ans-. Due to its high calorific value, it's employed as a rocket fuel. Welding with an oxygen-hydrogen flame is possible. It's also used to make nitric acid, ammonia, hydrochloric acid and other compounds. It is also used as a reducing agent.

3. 3.What are the differences between hard water and soft water as per Class 11 Hydrogen notes?

Ans- Hard water contain many minerals and when this water is combined with soap, no lather is produced. It contains Calcium and magnesium ions. But when soap is mixed with soft water, lather forms. Soft water contains sodium ions.

4. 4. Why is water a good solvent for polar or ionic substances?

Ans- Water molecules are extremely polar in nature. A considerable amount of hydration energy is released when ionic compounds are combined in water. This energy is higher than the energy required to break the water molecules. As a result of the high hydration energy, ionic compounds solvate in water.

5. 5.What are hydrides?

Ans- Hydrogen compounds of metals and nonmetals are known as hydrides.


Get answers from students and experts

A block of mass 0.50 kg is moving with a speed of 2.00 ms-1 on a smooth surface. It strikes another mass of 1.00 kg and then they move together as a single body. The energy loss during the collision is

Option 1)

0.34\; J

Option 2)

0.16\; J

Option 3)

1.00\; J

Option 4)

0.67\; J

A person trying to lose weight by burning fat lifts a mass of 10 kg upto a height of 1 m 1000 times.  Assume that the potential energy lost each time he lowers the mass is dissipated.  How much fat will he use up considering the work done only when the weight is lifted up ?  Fat supplies 3.8×107 J of energy per kg which is converted to mechanical energy with a 20% efficiency rate.  Take g = 9.8 ms−2 :

Option 1)

2.45×10−3 kg

Option 2)

 6.45×10−3 kg

Option 3)

 9.89×10−3 kg

Option 4)

12.89×10−3 kg


An athlete in the olympic games covers a distance of 100 m in 10 s. His kinetic energy can be estimated to be in the range

Option 1)

2,000 \; J - 5,000\; J

Option 2)

200 \, \, J - 500 \, \, J

Option 3)

2\times 10^{5}J-3\times 10^{5}J

Option 4)

20,000 \, \, J - 50,000 \, \, J

A particle is projected at 600   to the horizontal with a kinetic energy K. The kinetic energy at the highest point

Option 1)


Option 2)

\; K\;

Option 3)


Option 4)


In the reaction,

2Al_{(s)}+6HCL_{(aq)}\rightarrow 2Al^{3+}\, _{(aq)}+6Cl^{-}\, _{(aq)}+3H_{2(g)}

Option 1)

11.2\, L\, H_{2(g)}  at STP  is produced for every mole HCL_{(aq)}  consumed

Option 2)

6L\, HCl_{(aq)}  is consumed for ever 3L\, H_{2(g)}      produced

Option 3)

33.6 L\, H_{2(g)} is produced regardless of temperature and pressure for every mole Al that reacts

Option 4)

67.2\, L\, H_{2(g)} at STP is produced for every mole Al that reacts .

How many moles of magnesium phosphate, Mg_{3}(PO_{4})_{2} will contain 0.25 mole of oxygen atoms?

Option 1)


Option 2)

3.125 × 10-2

Option 3)

1.25 × 10-2

Option 4)

2.5 × 10-2

If we consider that 1/6, in place of 1/12, mass of carbon atom is taken to be the relative atomic mass unit, the mass of one mole of a substance will

Option 1)

decrease twice

Option 2)

increase two fold

Option 3)

remain unchanged

Option 4)

be a function of the molecular mass of the substance.

With increase of temperature, which of these changes?

Option 1)


Option 2)

Weight fraction of solute

Option 3)

Fraction of solute present in water

Option 4)

Mole fraction.

Number of atoms in 558.5 gram Fe (at. wt.of Fe = 55.85 g mol-1) is

Option 1)

twice that in 60 g carbon

Option 2)

6.023 × 1022

Option 3)

half that in 8 g He

Option 4)

558.5 × 6.023 × 1023

A pulley of radius 2 m is rotated about its axis by a force F = (20t - 5t2) newton (where t is measured in seconds) applied tangentially. If the moment of inertia of the pulley about its axis of rotation is 10 kg m2 , the number of rotations made by the pulley before its direction of motion if reversed, is

Option 1)

less than 3

Option 2)

more than 3 but less than 6

Option 3)

more than 6 but less than 9

Option 4)

more than 9

Back to top