NCERT Solutions for Class 11 Chemistry Chapter 9 - Hydrogen
Hydrogen holds a uniquely special place in the periodic table - it sits at the very top, yet it does not comfortably belong to any single group. This duality makes Chapter 9 of Class 11 Chemistry both interesting and a little tricky. Students often get confused between the properties of atomic hydrogen, nascent hydrogen, and molecular hydrogen, or mix up the chemistry of different types of hydrides.
The NCERT solutions for Class 11 Chemistry Chapter 9 Hydrogen on Myclass24 are designed to resolve exactly these confusions. Each question is answered with clear reasoning - you will understand not just what the answer is, but why it is correct. The solutions follow the NCERT pattern, making them ideal for board exam preparation as well as a strong foundation for competitive exams. From isotopes of hydrogen to the anomalous properties of water and the industrial production of hydrogen, every concept is covered in precise, student-friendly language.
Download NCERT Solutions for Class 11 Chemistry Chapter 9 Hydrogen PDF
The complete PDF of NCERT Solutions for Class 11 Chemistry Chapter 9 Hydrogen is available for free download on Myclass24. It includes solutions to all exercise and in-text questions with proper chemical equations and explanations on isotopes, hydrides, water, and hydrogen peroxide.
Chapter 9 Hydrogen - Concepts, Facts and Key Tables
Hydrogen is the most abundant element in the universe, making up about 75% of all normal matter by mass, yet on Earth it is rarely found in the free state. The NCERT chapter on Hydrogen begins with its unique position in the periodic table - it resembles alkali metals (1 valence electron, forms H+) but also halogens (needs 1 electron to complete its shell, forms H-). This dual nature makes placement ambiguous. The chapter covers three isotopes: Protium (H-1), Deuterium (H-2 or D), and Tritium (H-3 or T). Tritium is radioactive with a half-life of about 12.3 years. One can check out all chapters of NCERT Solutions for Class 11 Chemistry and all subjects of NCERT Solutions for Class 11 from the Myclass24 page.
Preparation methods discussed include the reaction of metals with dilute acids, electrolysis of water, and industrial methods like steam reforming of methane (CH4 + H2O = CO + 3H2) and the water-gas shift reaction. Hydrogen's chemical properties include its reactions with halogens (forming HX), oxygen (forming water in a highly exothermic reaction), nitrogen (Haber process), and metals/non-metals to form hydrides.
Hydrides are classified into three types: ionic (saline) hydrides formed with highly electropositive metals (e.g. NaH, CaH2), covalent hydrides formed with non-metals (e.g. HCl, H2O, NH3), and metallic (interstitial) hydrides formed with d- and f-block elements. Water, the oxide of hydrogen, is given special attention - its anomalous properties such as high boiling point, high surface tension, maximum density at 4 degrees C, and ability to act as both acid and base are discussed. Hydrogen peroxide (H2O2) is another important compound, with its structure, preparation, properties, and uses covered in detail. The chapter also touches on the future of hydrogen as a clean fuel (hydrogen economy).
Isotopes of Hydrogen
| Isotope | Symbol | Protons | Neutrons | Nature |
| Protium | H-1 | 1 | 0 | Stable; most abundant (99.985%) |
| Deuterium | H-2 (D) | 1 | 1 | Stable; used in heavy water (D2O) |
| Tritium | H-3 (T) | 1 | 2 | Radioactive; half-life 12.3 years |
Classification of Hydrides
| Type | Formed With | Examples | Key Property |
| Ionic (Saline) | Group 1 and 2 metals | NaH, CaH2, LiH | Release H2 with water; H- ion present |
| Covalent (Molecular) | Non-metals, metalloids | HCl, H2O, NH3, SiH4 | Mostly gases or volatile liquids |
| Metallic (Interstitial) | d- and f-block metals | TiH1.73, PdH0.57 | Non-stoichiometric; H occupies lattice voids |
Anomalous Properties of Water
| Property | Value or Fact |
| Boiling Point | 100 degrees C (unusually high due to H-bonding) |
| Density Maximum | At 4 degrees C (1000 kg/m3) |
| Specific Heat | 4.18 J/g.K (highest among common liquids) |
| Dipole Moment | 1.85 D |
| Bond Angle (H2O) | 104.5 degrees |
| Self-ionisation constant Kw | 1 x 10-14 at 25 degrees C |
FAQs for NCERT Solutions Class 11 Chemistry Chapter 9 Hydrogen
Hydrogen is considered unique because it shows similarities with both alkali metals and halogens. It has one electron in its outermost shell like alkali metals but also requires one electron to complete its shell like halogens. Hydrogen is the most abundant element in the universe and plays a significant role in chemical and biological processes. It exists in different forms and participates in a wide variety of reactions. Understanding hydrogen helps students learn about periodic classification, bonding, and industrial chemistry. Due to its unique position in the periodic table, hydrogen remains one of the most extensively studied elements in chemistry.
Hydrogen has three isotopes: protium, deuterium, and tritium. Protium contains one proton and no neutron, making it the most abundant isotope. Deuterium contains one proton and one neutron, while tritium contains one proton and two neutrons and is radioactive. Although these isotopes have similar chemical properties, their physical properties differ due to variations in mass. Deuterium is widely used in scientific research and nuclear reactors, while tritium has applications in radioactive tracing and fusion research. Questions related to hydrogen isotopes are common in examinations because they help students understand atomic structure and isotopic variations.
Hydrogen can be prepared through several methods depending on the scale of production. In laboratories, hydrogen is commonly produced by reacting metals such as zinc with dilute acids. Industrially, hydrogen is manufactured through steam reforming of natural gas, electrolysis of water, and coal gasification processes. Each method has its advantages and applications depending on cost and efficiency. Understanding these preparation methods helps students connect theoretical chemistry with industrial applications. Questions on hydrogen production frequently appear in examinations because they demonstrate the practical significance of chemistry in energy generation and manufacturing industries.
Hydrogen has numerous applications in industries, energy production, and scientific research. It is used in the manufacture of ammonia, hydrogenation of vegetable oils, petroleum refining, and fuel cells. Hydrogen is also considered a promising clean fuel because its combustion produces water rather than harmful pollutants. In space exploration, liquid hydrogen serves as rocket fuel. Understanding the uses of hydrogen helps students appreciate its importance in modern technology and sustainable energy development. Examination questions often focus on industrial applications, environmental benefits, and the future potential of hydrogen as an alternative energy source.