In This Post we are providing Chapter-2 Hydrogen NCERT MOST IMPORTANT QUESTIONS for Class 11 CHEMISTRY which will be beneficial for students. These solutions are updated according to 2021-22 syllabus. These MCQS can be really helpful in the preparation of Board exams and will provide you with a brief knowledge of the chapter.
NCERT MOST IMPORTANT QUESTIONS ON HYDROGEN
1.Why does hydrogen occupy unique position in the periodic table?
Ans. Inspite of the fact that hydrogen, to a certain extent resembles both with alkali metals (ns’) and halogens (ns2 np5), it differs from them as well. Hydrogen has very small size as a consequence H+ does not exist freely and is always associated with other atoms or molecules. Thus, it is unique in behaviors and is therefore, best placed separately in the periodic table.
2.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 properly of these isotopes differ considerably due to their large mass differences.
3.How can the production of dlhydrogen obtained from ‘coal gasification be increased’?
Ans. By reacting carbon monoxide of syngas mixtures with steam in the presence of iron chromate as catalyst
4.Why is dihydrogen used an fuel cells for generating electrical energy?
Ans. Because it does not produce any pollution and releases greater energy per unit mass of fuel in comparison to gasoline or any other fuel.
5.What is understood by hydrogenation?
Ans. Hydrogenation is used for the conversion of polyunsaturated oils into edible fats.
6.Which fuel is used as a rocket fuel?
Ans. Dihydrogen is used as a rocket fuel in space research.
7.What happens when sodium hydride reacts with water?
Ans. Saline hydride (sodium hydride) react violently with water producing dihydrogen gas 
8.What is the geometry of the compound formed by group 14 to form molecular hydride?
Ans. Tetrahedral in structure.
9.What are the characteristic features of ionic or saline hydrides?
Ans. The ionic hydrides are crystalline, non – volatile non – conducting in solid state. However their melts conduct electricity.
10.Which gas is produced on electrolysis of ionic hydride?
Ans. Dihydrogen gas is produced at the anode on electrolysis of ionic hydride.
11.How does H+ ion forms hydronium ion (OH3+) in water?
Ans. In water H+ ion forms a covalent bond with H2O and forms hydronium ion, (H3O+).
12.Show with reaction the amphoteric nature of water.
Ans. Water acts as an acid with NH3 and base with H2S
13.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
14.Why does hard water not form lather with soap?
Ans. Hard water does not produce lather with soap readily because the cations (Ca2+ and Mg2+) present in hard water react with soap to precipitate of tcalcium and magnesium salts of fatly acids.
From hard water sodium stearate form Ca/Mg stearate
15.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 anion gets weakened. Thus water molecules are able to remove ions from the lattice site using in dipole forces easily.
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