NCERT exemplar class 11 Chemistry Solutions Chapter 9 provides the students with a compact and efficiently designed format for studying about the copious amounts of facts and information available about the element hydrogen which in many ways is the most important element in the periodic table and is essential for the students to be well versed with in order to have a strong foundation in the subject and implementing the knowledge learned about hydrogen. NCERT Exemplar Class 11 Chemistry Chapter 9 solutions are around hydrogen and its various peculiar properties which explain why the element reacts in certain ways in chemical reactions and how its isotopic and chemical properties pave the way for the other elements in reactions.
Also read - NCERT Solutions for Class 11 Chemistry Chapter 9 Hydrogen
NCERT exemplar class 11 Chemistry solutions chapter 9: MCQ (Type 1)
Hydrogen resembles halogens in many respects for which several factors are responsible. Of the following factors which one is most important in this respect?
(i) Its tendency to lose an electron to form a cation.
(ii) Its tendency to gain a single electron in its valence shell to attain stable electronic configuration.
(iii) Its low negative electron gain enthalpy value.
(iv) Its small size.
The answer is the option (ii) Its tendency to gain a single electron in its valence shell to attain stable electronic configuration.
Hydrogen resembles halogens as halogens with the configuration of in the seventeenth group, also harbour the ability to accept one electron and configure as an inert gas. Similarly, Hydrogen also can accept an electron to configure itself like helium.
Why does ion always get associated with other atoms or molecules?
(i) Ionisation enthalpy of Hydrogen resembles that of alkali metals.
(ii) Its reactivity is similar to halogens.
(iii) It resembles both alkali metals and halogens.
(iv) Loss of an electron from hydrogen atom results in a nucleus of very small size as compared to other atoms or ions. Due to the small size, it cannot exist free.
The answer is the option (iv) Loss of an electron from hydrogen atom results in a nucleus of very small size as compared to other atoms or ions. Due to the small size, it cannot exist freely.
A positive hydrogen ion is extremely small in size and cannot exist as a single alone atom but instead only exists as an association with other elements.
Hydrogen peroxide is _________.
(i) an oxidising agent
(ii) a reducing agent
(iii) both an oxidising and a reducing agent
(iv) neither oxidising nor reducing agent
The answer is the option (iii) both an oxidizing and a reducing agent
We have seen examples of acting as both the reducing and oxidising agent.
Only one element of ________ forms hydride.
(i) group 6
(ii) group 7
(iii) group 8
(iv) group 9
The answer is the option (i) Group 6
Only Chromium (Cr) is the element in group 6, capable of forming a hydride.
NCERT exemplar class 11 Chemistry solutions chapter 9: MCQ (Type 2)
Which of the following statements are not true for Hydrogen?
(i) It exists as a diatomic molecule.
(ii) It has one electron in the outermost shell.
(iii) It can lose an electron to form a cation which can freely exist
(iv) It forms a large number of ionic compounds by losing an electron.
The answer is the option (iii) & (iv), i.e. it can lose an electron to form a cation which can freely exist, and it forms a large number of ionic compounds by losing an electron.
Hydrogen cannot form ionic compounds by giving an electron but instead forms many covalent bonds by the sharing of electrons.
Which of the following statement(s) is/are correct in the case of heavy water?
(i) Heavy water is used as a moderator in a nuclear reactor.
(ii) Heavy water is more effective as a solvent than ordinary water.
(iii) Heavy water is more associated than ordinary water.
(iv) Heavy water has a lower boiling point than ordinary water.
The answer is the option (i) and (iii), i.e. Heavy water is used as a moderator in a nuclear reactor, and Heavy water is more associated than ordinary water.
It is associated with water as it has a higher mass as well as facilitates as a moderator in exchange reactions.
Which of the following statements about Hydrogen are correct?
(i) Hydrogen has three isotopes, of which protium is the most common.
(ii) Hydrogen never acts as cation in ionic salts.
(iii) Hydrogen ion, , exists freely in solution.
(iv) Dihydrogen does not act as a reducing agent.
The answer is the option (i) and (ii), i.e. Hydrogen has three isotopes of which protium is the most common and Hydrogen never act as a cation in ionic salts.
Protium, one of Hydrogen’s 3 isotopes is the most common as well as due to the small atomic size, it doe does not act as a cation but is associated with other molecules and compounds.
Some of the properties of water are described below. Which of them is/are not correct?
(i) Water is known to be a universal solvent.
(ii) Hydrogen bonding is present to a large extent in liquid water.
(iii) There is no hydrogen bonding in the frozen state of water.
(iv) Frozen water is heavier than liquid water.
The answer is the option (iii) and (iv). There is no hydrogen bonding in the frozen state of water, and Frozen water is heavier than liquid water.
Water exhibits different properties in different states due to hydrogen bonding, which exists in a water molecule. Ice is lighter than water due to the fact that there are empty spaces in the tetrahedrons of the hydrogen bonds.
Hardness of water may be temporary or permanent. Permanent hardness is due to the presence of
(i) Chlorides of Ca and Mg in water
(ii) Sulphates of Ca and Mg in water
(iii) Hydrogen carbonates of Ca and Mg in water
(iv) Carbonates of alkali metals in water
The answer is the option (i) and (ii) Chlorides of Ca and Mg in water and sulphate of Ca and Mg in water.
Two salts of calcium and magnesium when found as compounds of carbonate, chloride and sulphate dissolve in the water and make it hard.
Which of the following statements is correct?
(i) Elements of group 15 form electron deficient hydrides.
(ii) All elements of group 14 form electron precise hydrides.
(iii) Electron precise hydrides have tetrahedral geometries.
(iv) Electron rich hydrides can act as Lewis acids.
The answer is the option (ii) and (iii) All elements of group 14 form electron precise hydrides and electron precise hydrides have tetrahedral geometries.
All group 14 elements are tetrahedral in terms of geometry and form their own Lewis structures. They are electron precise hydrides which have enough number of electrons.
Which of the following statements is correct?
(i) Hydrides of group 13 act as Lewis acids.
(ii) Hydrides of group 14 are electron deficient hydrides.
(iii) Hydrides of group 14 act as Lewis acids.
(iv) Hydrides of group 15 act as Lewis bases.
The answer is the option (i) and (iv), i.e. Hydrides of group 13 act as Lewis acids and Hydrides of group 15 act as Lewis bases.
All the elements of group 13 are hydrides which act as Lewis acids since they form electron-deficient compounds. The group 14 elements are known as electron-rich hydrides and thus have extra electrons which are present in the form of lone pairs. Groups 15 to 17 have elements which form compounds that have 1 to 3 lone pairs and therefore act as Lewis bases.
(i) Metallic hydrides are deficient of Hydrogen.
(ii) Metallic hydrides conduct heat and electricity.
(iii) Ionic hydrides do not conduct electricity in solid-state.
(iv) Ionic hydrides are very good conductors of electricity in solid-state.
The answer is the option (i), (ii), and (iii) Metallic hydrides are deficient of Hydrogen, Metallic hydrides conduct heat and electricity, and Ionic hydrides do not conduct electricity in solid-state.
Hydride and not volatile or conductive in the solid-state but are crystalline instead. While metallic hydrides are non-stoichiometric hydrides. They only conduct electricity in their molten state.
What are metallic/interstitial hydrides? How do they differ from molecular hydrides?
Metallic hydrides are usually formed by d and f block elements. These hydrides are good conductors of heat and electricity; they lack Hydrogen, which makes them non-stoichiometric. These differ from molecular hydrides as they are formed by s, p block elements while the metals of group 7, 8, 9 do not form hydrides. Molecular hydrides are not good conductors of electricity or heat, unlike the metallic hydrides. They are also volatile compounds which have low melting and boiling points, but metallic hydrides, on the other hand, are hard in texture and have a certain metallic lustre.
(i) Lakes freeze from the top towards the bottom.
(ii) Ice floats on water.
The lake freezes from top to bottom because the temperature during winter keeps on decreasing, and the movement of water happens in such a way that the cold water is heavier and so it sinks to the bottom. While warm water replaces it by coming on the surface. The process repeats until the temperature decreases below 4 degrees and the lake keep on freezing from top to bottom.
Density of ice is less than water due to its structure which forms empty spaces between the water molecules, 4 atoms of Hydrogen surround 1 of oxygen, and therefore make ice float on water
What do you understand by the term ‘auto protolysis' of water? What is its significance?
Autoprotolysis is the process when two similar molecules react with each other to produce products that are called ions with Proton transfer. Autoprotolysis of water means the transfer of one Proton from a certain molecule to another. This explains the ability of water act as both acid and base. Therefore, making it amphoteric in nature.
Discuss briefly de-mineralisation of water by ion exchange resin.
Demineralization of water means that all the soluble salts present in water are removed through cation and anion exchange. In the cation exchange process, cations of sodium, calcium and magnesium replace those of Hydrogen. While the anion exchange process exchanges OH. This both combine to produce water.
Molecular hydrides are classified as electron-deficient, electron precise and electron-rich compounds. Explain each type with two examples.
There are three major types of molecular hydrides.
Electron precise hydrides are the ones that have just enough exact number of electrons to facilitate normal covalent bonds. These are the hydrides which are primarily comprised of group 14 elements: .
Electron deficient hydrides are the ones which do not possess enough number of electrons to facilitate normal covalent bonds. Hydrides of group 13 a prime examples; .
Electron rich hydrides are ones which have an excess number of electrons remaining after normal covalent bonds. Elements of group 15 16 17 are prime examples; .
Explain why HCl is a gas and HF is a liquid.
F is a stronger electronegative than chlorine, and so forms a stronger bond with Hydrogen than chlorine. In order to break HF bonds, more energy is required as compared to break HCl bonds. This is the reason why HF has a higher boiling point than HCl and is a liquid at room temperature.
Give reasons why Hydrogen resembles alkali metals?
Hydrogen has a specific unique electronic configuration which is similar to alkali metals but belongs to group 1 in the periodic table. Its strong nature like the alkali metals due to its configuration makes it give one electron to combine to form unipositive ions.
Hydrogen generally forms covalent compounds. Give reason.
Due to its configuration, Hydrogen also resembles certain halogens, given its ionization enthalpy. Therefore, when acting as a halogen, it forms hydrides by combining with the elements to form a diatomic molecule along with covalent compounds.
Why is the ionisation enthalpy of Hydrogen higher than that of sodium?
Hydrogen has a higher ionization enthalpy than sodium because sodium has a different configuration that is in the last shell, the electron is in 3s, which if lost, the configuration resembles neon, which is the noble gas. However, with Hydrogen, the case is different, and the electron is in the 1s orbital which on losing doenot amount to attainement of noble gas configuation.
What is the importance of heavy water?
Heavy water is composed by electrolysis of water or through the fertilizer industries. It is a the great catalyst in nuclear reactors and can be used to study reactions.
Why is water molecule polar?
The polar nature of the water molecule is due to the structure of the bent molecule and bond length of 95.7pm and the angle of 104.5.
Why does hard water not form lather with soap?
Hard water contains soluble salts which make it rough and form a precipitate when used along with soap. Due to harsh chemicals dissolve in it, hard water is unsuitable for washing and laundry. The accumulation of salts makes it unsuitable for boilers is well.
Match Column I with Column II for the given properties/applications mentioned therein.
(a) Used in the name perhydrol
(b) Can be reduced to dihydrogen by NaH.
(c) Can be used in hydroformylation of olefin.
(d) Can be used in cutting and welding.
(i) → (d)
(ii) → (c)
(iii) → (b)
(iv) → (a)
NCERT Exemplar Class 11 Chemistry Solutions Chapter 9: Long Answer Type
Atomic Hydrogen combines with almost all elements, but molecular Hydrogen does not. Explain.
Molecular Hydrogen is very stable, but atomic Hydrogen is very reactive, and the chemical behaviour of any molecule is determined by the bond dissociation enthalpy. In dihydrogen, the hydrogen bond dissociation enthalpy is very high, and therefore it only reacts with a certain number of elements.
How will you concentrate ? Show differences between structures of and by drawing their spatial structures. Also mention three important uses of .
To obtain hydrogen peroxide, you can use evaporation and barium peroxide by removing excess water. To make it more concentrated, use the process of distillation, and low pressure and then pure hydrogen peroxide can be obtained.
The spatial structures of and are as follows: -
Three important uses of are as follows: -
Peroxide is used as a disinfectant and antiseptic in the market.
It is used to produce other chemicals in the industry and is also applied as a commercial bleaching product.
It finds great application in the textile industry.
For students who wish to be able to reach out for queries and NCERT solutions from this chapter at any time so that they develop a strengthened understanding of the topic, there is a solution. Students can avail the option of NCERT Exemplar Class 11 Chemistry Solutions Chapter 9 PDF download for future studies.
Also read - NCERT Solutions for Class 11 Chemistry
Topics and Subtopics in NCERT exemplar class 11 Chemistry Solutions Chapter 9 Hydrogen
Class 11 Chemistry NCERT Exemplar solutions Chapter 9 include the following topics:
Position Of Hydrogen In The Periodic Table
Isotopes Of Hydrogen
Preparation Of Dihydrogen, H2
Laboratory Preparation Of Dihydrogen
Commercial Production Of Dihydrogen
Properties Of Dihydrogen
Uses Of Dihydrogen
Ionic Or Saline Hydrides
Covalent Or Molecular Hydride
Metallic Or Non-stoichiometric (Or Interstitial ) Hydrides
Physical Properties Of Water Ex
Structure Of Water
Structure Of Ice
Chemical Properties Of Water
Hard And Soft Water
Hydrogen Peroxide (H202)
Heavy Water, D20
Dihydrogen as a Fuel
What the students will learn from NCERT exemplar class 11 Chemistry Solutions Chapter 9 Hydrogen
With the detailed and specific contents of Class 11 Chemistry NCERT exemplar solutions chapter 9 the students have the opportunity to have a detailed study of the element hydrogen. This chapter allows the students to extend their horizons and knowledge base about the chemical properties, structure, and physical properties of water which tend to further explain why hydrogen reacts in a specific manner. NCERT exemplar solutions for class 11 Chemistry chapter 9 also discusses the various forms of existence of hydrogen such as Dihydrogen and its production and chemical and physical properties along with its preparation process. Another important concept discussed is the preparation, physical and chemical properties of hydrogen peroxide. Heavy water and the practical application of dihydrogen as a fuel have also been explored in the chapter.
NCERT Exemplar Class 11 Chemistry Solutions Chapter-Wise
Important topics to cover from NCERT exemplar class 11 Chemistry Solutions Chapter 9 Hydrogen
Ø The students who refer to NCERT Exemplar solutions for class 11 Chemistry chapter 9 get to indulge in the in-depth study of hydrogen and all of its properties which include- occurrence, physical and chemical properties and its different forms of existence which include dihydrogen, hydrogen peroxide etc.
Ø Another area of information discussed is around the position of hydrogen in the periodic table and how it affects and influences the chemical reactions of various elements. The students are informed about the practical applications of all the different forms of hydrogen.
Ø The students will also be educated about the crucial facts about the physical and chemical properties, practical applications, storage and structure of the various forms and isotopes of hydrogen such as dihydrogen, hydrides, etc.
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