Vishal BaghelExecutive Content Operations
Hydrogen is the lightest known elements and first in the periodic table. It's the most abundant chemical element, estimated to contribute 75% of the mass of the universe. A vast numbers of hydrogen atoms are contained in water, plants, animals and, of course, humans. A colourless, odourless gas, it has the lowest density of all gases.
Hydrogen gas is the clean fuel of the future, generated from water and returning to water when it is oxidised. The NCERT class 11 Chemistry Hydrogen chapter will cover its occurrence, preparation in laboratory, properties, and uses as fuel. Candidates can check here NCERT class 11 Chemistry solution Hydrogen chapter to understand the basic concepts, analytical and conceptual skills to score good marks in the exam. The solutions provided here have been prepared by the subject matter experts. Students preparing for entrance exams can refer NCERT Solutions Chemistry class 12.
Hydrogen- Topics Covered
Students can check below the list of all topics that are covered in NCERT Class 11 Hydrogen chapter.
- Position of Hydrogen in the Periodic Table
- Dihydrogen, H2
- Occurrence
- Isotopes of Hydrogen
3. Preparation of Dihydrogen, H2
- Laboratory Preparation of Dihydrogen
- Commercial Production of Dihydrogen
4. Properties of Dihydrogen
- Physical Properties
- Chemical Properties
- Uses of Dihydrogen
- Hydrides
- Ionic or Saline H ydrides
- Covalent or Molecular Hydride
- Metallic or Non-stoichiometric (or Interstitial) Hydrides
6. Water Ex
- Physical Properties of Water Ex
- Structure of Water
- Structure of Ice
- Chemical Properties of Water
- Hard and Soft Water
- Temporary Hardness
- Permanent Hardness
- Hydrogen Peroxide (H2O2)
- Preparation
- Physical Properties
- Structure
- Chemical Properties
- Storage
- Uses
- Heavy Water, D2O
- Dihydrogen as a Fuel
Hydrogen Additonal Questions:
9.1.Assertion: H2O2 is stored in wax-lined glass or plastic vessels in dark.
Reason:H2O2 decomposes slowly on exposure to light.
Answer: (a) H2O2 decomposes slowly on exposure to light.
2 H2O2 (l) → 2H2O(l) + O2 (g)
In the presence of metal surfaces or traces ofalkali (present in glass containers), the above
reaction is catalysed. It is, therefore, stored inwax-lined glass or plastic vessels in dark.
9.2.Assertion: H+ does not exist freely and is always associated with other atoms or molecules.
Reason:H+ form hydrides.
Answer:(b) Loss of the electron from hydrogen atomresults in nucleus (H+) of ~1.5×10–3 pm size.This is extremely small as compared to normalatomic and ionic sizes of 50 to 200pm. As a consequence, H+ does not exist freely and isalways associated with other atoms ormolecules.
9.3.Assertion: Lithium hydride used in the synthesis of other useful hydrides.
Reason: Lithium hydride is very reactive at moderate temperatures with O2 or Cl2.
Answer:(c) Lithium hydride is rather unreactive atmoderate temperatures with O2 or Cl2. It is,therefore, used in the synthesis of other usefulhydrides, e.g.,
8LiH + Al2Cl6 → 2LiAlH4 + 6LiCl
2LiH + B2H6 → 2LiBH4
9.4.Assertion: An ice cube floats on water.
Reason: Density of ice is more than that of water.
Answer:(c) The crystalline form of water is ice. Atatmospheric pressure ice crystallises in the hexagonal form, but at very low temperatures it condenses to cubic form. Density of ice is less than that of water. Therefore, an ice cube floats on water. In winter season ice formed on the surface of a lake provides thermal insulation which ensures the survival of the aquatic life. This fact is of great ecological significance.
9.5.Assertion: Hard water is desirable for laundry.
Reason:Soap containing sodium stearate (C17H35COONa) reacts with hard water to precipitate out Ca/Mg stearate.
Ans: (d) Hard water forms scum/precipitate with soap. Soap containing sodium stearate(C17H35COONa) reacts with hard water to precipitate out Ca/Mg stearate.It is, therefore, unsuitable for laundry. It is harmful for boilers as well, because of deposition of salts in the form of scale. This reduces the efficiency of the boiler.
MCQs:
9.1. Hydrogen peroxide in the name of perhydrolis used as
(a) antipyretic
(b) antiseptic
(c) analgesic
(d) all of the above
Answer:(b) antiseptic
9.2. Choose the incorrect statement:
(a) Hard water is not suitable for laundry.
(b) Temporary hardness can be removed by boiling.
(c) Calgon is used for removing permanent hardness of water.
(d) Calgon forms precipitates with Ca2+ and Mg2+.
Answer: (d) Calgon forms precipitates with Ca2+ and Mg2+.
9.3. Choose the incorrect statement:
(a) H+ can exist freely.
(b) Hydrogen combines with other elements by losing, gaining, or sharing of electrons.
(c) Hydrogen forms electrovalent and covalent bonds with other elements.
(d) H+ isextremely small as compared to normal atomic and ionic sizes of 50 to 200 pm.
Answer: (a) H+ can exist freely.
9.4. Choose the incorrect statement.
(a) H2O2has planar structure.
(b) Alkali oxides present in glass catalyse the decomposition of H2O2.
(c) Decomposition of H2O2 is a disproportionation reaction.
(d) H2O2 molecule simultaneously undergoes oxidation and reduction.
Answer: (a) H2O2 has planar structure.
9.5. While converting vegetable oil into vegetable ghee, H2 is used as a
(a) oxidising agent (b) reducing agent (c) both (d) none
Answer: (b) reducing agent
Questions and Answers:
9.1. What property of dihydrogen makes its use in atomic hydrogen torch?
Answer:The H–H bond dissociation enthalpy of dihydrogen (435.88 kJ mol–1) is the highest
for a single bond between two atoms of any elements. This property is made use of in the
atomic hydrogen torch which generates a temperature of ~4000K and is ideal for welding
of high melting metals.
9.2. Why is dihydrogen inactive at room temperature?
Answer:Dihydrogen is inactive at room temperature because of very highnegative dissociation enthalpy, it combines with almost all the elements under appropriate
conditions to form hydrides.
9.3.List the uses of H2O2.
Answer: Some of the uses of H2O2 are listed below:
(i) In daily life it is used as a hair bleach andas a mild disinfectant. As an antiseptic it is sold in the market as perhydrol.
(ii) It is used to manufacture chemicals like sodium perborate and percarbonate,which are used in high quality detergents.
(iii) It is used in the synthesis of hydroquinone, tartaric acid and certain food products and pharmaceuticals (cephalosporin) etc.
(iv) It is employed in the industries as ableaching agent for textiles, paper pulp,leather, oils, fats, etc.
(v) Nowadays it is also used in Environmental(Green) Chemistry. For example, in pollution control treatment of domestic and industrial effluents, oxidation of cyanides, restoration of aerobic conditions to sewage wastes, etc.
9.4. Explain the basic principle of Hydrogen economy.
Answer: The basic principle of hydrogen economy is the transportation and storage ofenergy in the form of liquid or gaseous dihydrogen. Advantage of hydrogen economyis that energy is transmitted in the form ofdihydrogen and not as electric power. It is for the first time in the history of India that a pilot project using dihydrogen as fuel was launched in October 2005 for running automobiles.Initially 5% dihydrogen has been mixed in CNG for use in four-wheeler vehicles. The percentage of dihydrogen would be gradually increased to reach the optimum level. Nowadays, it is also used in fuel cells for generation of electric power. It is expected that economically viable and safe sources of dihydrogen will be identified in the years to come, for its usage as a common source ofenergy.
9.5. What are hydrides? Name the different types of hydrides.
Answer:Dihydrogen, under certain reaction conditions, combines with almost all elements, except noble gases, to form binary compounds, called hydrides. If ‘E’ is the symbol of an element then hydride can be expressed as EHx (e.g., MgH2) or EmHn (e.g., B2H6).
The hydrides are classified into three categories:
(i) Ionic or saline or saltlike hydrides
(ii) Covalent or molecular hydrides
(iii) Metallic or non-stoichiometric hydrides
9.6. What are interstitial hydrides? Give two examples. Write two uses of interstitial hydrides.
Answer: Many transition and inner-transition metals absorb hydrogen into the interstices of their lattices to yield metal like hydrides also called the interstitial hydrides. These hydrides are generally non stoichiometric and their composition vary with temperature and pressure.
For example, TiH1.73, CeH2.7
Two uses of interstitial hydrides are:
(i) In the storage of H2.
(ii) Catalyst for hydrogenation reaction.
9.7. Water molecule is bent, not linear. Explain?
Answer: In water molecule, O is SP3 hybridized. Due to stronger lone pair-lone pair repulsion than bond pair-bond pair repulsions, the H-O-H bond angle decreases from 109.5° to 104.5°. Thus, water is bent molecule.
9.8. What is meant by hard water? How come boiling remove the temporary hardness of water?
Answer: Water which does not produce lathers with soap is known as hard water. Hardness is due to the presence of bicarbonates, sulphates and chlorides of Ca2+ and Mg2+.
On boiling, the bicarbonates of calcium and magnesium decompose to insoluble carbonate which can be removed by filtration.
9.9. Give two advantages of using hydrogen over gasoline as a fuel.
Answer: 1. High heat of combustion.
2. It is pollution free.
9.10. How is dihydrogen prepared from water by using a reducing agent?
Answer: Dihydrogen is prepared from water by the action of alkali metals like Na and K which is a strong reducing agent.
2Na + 2H2O → 2NaOH + H2
2K + 2H2O → 2KOH + H2
Hydrogen Solutions and FAQs
Q 9.1. Justify the position of hydrogen in the periodic table on the basis of its electronic configuration.
A 9.1 Hydrogen has electronic configuration 1s1similar to the outer electronic configuration (ns1) of alkali metals, which belong to the first group of the periodic table. On the other hand, like halogens (with ns2np5) configuration belonging to the seventeenth group of the periodic table, it is short by one electron to the corresponding noble gas configuration, helium (1s2). Hydrogen, therefore, has resemblance to both alkali metals, which lose one electron to form unipositive ions, as well as with halogens, which gain one electron to form uni-negative ion. Like alkali metals, hydrogen forms oxides, halides and sulphides. However, unlike alkali metals, it has a very high ionization enthalpy and does not possess metallic characteristics under normal conditions. In terms of ionization enthalpy, hydrogen resembles more with halogens. Like halogens, it forms a diatomic molecule, combines with elements to form hydrides and a large number of covalent compounds. However, in terms of reactivity, it is very low as compared to halogens.
Q 9.2. Write the names of isotopes of hydrogen. What is the mass ratio of these isotopes?
A 9.2
Mass ratio of the isotopes = Protium: Deuterium: Tritium = 1: 2 :3
Q 9.3. Why does hydrogen occur in a diatomic form rather than in a monoatomic form under normal conditions?
A 9.3 In diatomic form, the K-shell of hydrogen is complete (1s2) and so it is quite stable. That is why hydrogen occur in a diatomic form rather than in a monoatomic form.
Q 9.4. How can the production of dihydrogen, obtained from ‘coal gasification’ be increased?
A 9.4
The production of dihydrogen in coal gasification can be increased by reacting CO present in syngas mixtures with steam in the presence of iron chromate as catalyst. This is called water-gas shift reaction. Synthesis gas or 'syngas' is produced from sewage, saw-dust, scrap wood, newspapers etc. The process of producing 'syngas' from coal is called 'coal gasification'.
CO(g) + H2O(g) → CO2(g) + H2(g)
With the removal of C02 by scrubbing with sodium arsenite solution the reaction shifts in the forward direction and thus, the production of dihydrogen will be increased.
Q 9.5. Describe the bulk preparation of dihydrogen by electrolytic method. What is the role of an electrolyte in this process?
A 9.5
In bulk, dihydrogen can be produced by electrolysis of acidified water using Platinum electrodes.
2H2O (l) → H2 (g) + O2 (g)
Electrolyte is added to increase the dissociation of water.
Q 9.6. Complete the following reactions.
A 9.6
(i) 3H2(g)+2MoO3 ⟶ Mo2O3+3H2O(l)
(ii) CO (g) + H2 (g) ⟶ CH3OH
(iii)C3H8 (g) + 3H2O(g) ⟶ 3CO + 7H2(g)
(iv) Zn (s) + NaOH (aq) ⟶ Na2ZnO2(s) + H2(g)
Q 9.7. Discuss the consequences of high enthalpy of H-H bond, in terms of chemical reactivity of dihydrogen.
A 9.7 This is due to its small atomic size and small bond length (74 pm) of H-H bond.H−H bond has very high bond enthalpy (435.9 kJ/mol) which results in low reactivity at room temperature. The reactivity is increased at high temperature or in presence of catalyst. Under these conditions, hydrogen reacts with many metals and non-metals to form hydrides.
Q 9.8. What do you understand by (i) electron-deficient, (ii) electron-precise, and (iii) electron-rich compounds of hydrogen? Provide justification with suitable examples.
A 9.8
(i) Electron deficient hydrides: Compounds in which central atom has incomplete octet, are called electron deficient hydrides. For example, BeH2, BH3 are electron deficient hydrides.
(ii) Electron precise hydrides: Those compounds in which exact number of electrons are present in central atom or the central atom contains complete octet are called precise hydrides e.g., CH4, SiH4, GeH4 etc. are precise hydrides.
(iii) Electron rich hydrides: Those compounds in which central atom has one or more lone pair of excess electrons are called electron rich hydrides, e.g.,NH3, H2O.
Q 9.9. What characteristics do you expect from an electron-deficient hydride with respect to its structure and chemical reactions?
A 9.9 It is expected to be a Lewis acid. They are likely to accept electrons to become stable. They can form coordinate bond with electron rich compound.
2NaH(s) + B2H6 (g) → 2Na+[BH4]- (s) (Sodium borohydride)
Q 9.10. Do you expect the carbon hydrides of the type (CnH2n+2) to act as ‘Lewis’ acid or base? Justify your answer.
A 9.10 Carbon hydrides of the type CnH2n+2 are electron precise hydrides. Because they have atom with exact number of electrons to form covalent bonds. Thus, they do not behave as Lewis acid or base. Since they have no tendency to accept or lose electrons.
Q 9.11. What do you understand by the term “non-stoichiometric hydrides”? Do you expect this type of hydrides to be formed by alkali metals? Justify your answer.
A 9.11 Those hydrides which do not have fix composition are called non-stoichiometric hydrides, and the composition varies with temperature and pressure. This type of hydrides is formed by d- and f-block elements. They cannot be formed by alkali metals because alkali metal hydrides form ionic hydrides.
Q 9.12. How do you expect the metallic hydrides to be useful for hydrogen storage? Explain.
A 9.12 Metallic hydrides are useful for ultra-purification of dihydrogen and as dihydrogen storage media. In metallic hydrides, hydrogen is adsorbed as H-atoms. Due to the adsorption of H atoms the metal lattice expands and become unstable. Thus, when metallic hydride is heated, it decomposes to form hydrogen and finely divided metal. The hydrogen evolved can be used as fuel.
Q 9.13. How does the atomic hydrogen or oxy-hydrogen torch function for cutting and welding purposes? Explain.
A 9.13 When hydrogen is burnt in oxygen the reaction is highly exothermic, it produces very high temperature nearly 4000°C which is used for cutting and welding purposes.
Q 9.14. Among NH3, H2O and HF, which would you expect to have highest magnitude of hydrogen bonding and why?
A 9.14 HF is expected to have highest magnitude of hydrogen bonding since, fluorine is most electronegative. Therefore, HF is the most polar.
Q 9.15. Saline hydrides are known to react with water violently producing fire. Can CO2, a well known fire extinguisher, be used in this case? Explain.
A 9.15 No. Because if saline hydrides react with water the reaction will be highly exothermic thus the hydrogen evolved in this case can catch fire. CO2 cannot be used as fire extinguisher because CO2 will get absorbed in alkali metal hydroxides.
Q 9.16. Arrange the following:
A 9.16
(i) CaH2, BeH2 and TiH2 in order of increasing electrical conductance.
(ii) LiH, NaH and CsH in order of increasing ionic character.
(iii) H-H, D—D and F—F in order of increasing bond dissociation enthalpy.
(iv) NaH, MgH2 and H2O in order of increasing reducing property.
A 9.16 (i) BeH2< TiH2 < CaH2
(ii) LiH
(iv) H2O < MgH2
Q 9.17. Compare the structures of H2O and H2O2.
A 9.17 In water, O is sp3 hybridized. Due to stronger lone pair-lone pair repulsions than bond pair-bond pair repulsions, the HOH bond angle decreases from 109.5° to 104.5°. Thus, water molecule has a bent structure.
H2O2 has a non-planar structure. The O—H bonds are in different planes. Thus, the structure of H2O2 is like an open book.
Q 9.18. What do you understand by the term ‘auto-protolysis’ of water? What is its significance?
A 9.18
Auto-protolysis means self-ionisation of water. It may be represented as
2H2O(l) + H2O(l) ⇌ H3O+(aq) + OH-(aq)
Acid 1 Base 2 Acid 2 Base 1
Due to auto-protolysis nature of water, it can act as an acid as well as base, i.e. amphoteric in nature.
Q 9.19. Consider the reaction of water with F2 and suggest, in terms of oxidation and reduction, which species are oxidised/reduced?
A 9.19 2F2(ag) + 2H2O(l)→ O2(g) + 4H+(aq) + 4F(aq)
In this reaction water acts as a reducing agent and itself gets oxidised to O2 while F2 acts as an oxidising agent and hence itself reduced to F– ions.
Q 9.20. Complete the following chemical reactions.
(i) PbS(s) + H2O2 (aq) →
(ii) MnO4– (aq) + H2O2 (aq) →
(iii) CaO(s) + H2O(g) →
(iv) AlCl3(g) + H2O(l)→
(v) Ca3N2(S) + H2O(l) →
Classify the above into (a) hydrolysis, (b) redox and (c) hydration reactions.
A 9.20 (i) PbS(s) +4H2O2(aq) → PbSO4(s) + 4H2O(l)
(ii) 2MnO4– (aq) +H2O2(aq) + 6H+(aq) → 2Mn (aq) + 8H2O(l) + 5O2(g)
(iii) CaO(s) + H2O(g) → Ca(OH)2(aq)
(iv) AlCl3(aq) + 3H2O(l) → Al(OH)3(s) + 3HCl (aq)
(v) Ca3N2(s) + H2O(l) → 3Ca(OH)2(aq) + 2NH3(aq)
(a) Hydrolysis reactions, (iii) (iv) and (v)
(b) Redox reactions (i) and (ii)
Q 9.21. Describe the structure of common form of ice.
A 9.21 Ice has crystalline structure which is highly ordered due to hydrogen bonding. It has hexagonal form at atmospheric pressure and cubic form at low temperature. Each O atom has tetrahedral geometry and is surrounded by 4 oxygen atoms each at a distance of 276 pm.
Q 9.22. What causes the temporary and permanent hardness of water?
A 9.22 Temporary hardness of water is due to the presence of bicarbonates of calcium and magnesium in water i.e., Ca(HCO3)2 and Mg(HCO3) in water. Permanent hardness of water is due to the presence of soluble chlorides and sulphates of calcium and magnesium i.e., CaCl2, CaSO4, MgCl2 and MgSO4
Q 9.23. Discuss the principle and method of softening of hard water by synthetic ion-exchange resins.
A 9.23 Cation exchange resins have large organic molecule with SO3H group which are insoluble in water. Ion exchange resin (RSO3H) is changed to RNa on treatment with NaCl. The resin exchange Na+ ions with Ca2+ and Mg2+ ions present in hard water and make it soft.
2RNa(s) + M2+(aq) ——> R2M(s) + 2Na+(aq), where, M = Mg, Ca.
The resins can be regenerated by adding aqueous NaCl solution.
Q 9.24. Write chemical reactions to show the amphoteric nature of water.
A 9.24 Water is amphoteric in nature because it acts as an acid as well as a base.
Amphoteric nature of water is represented by following chemical reactions.
(1) Water as a base:
H2O(l)+H2S(g)⇌H3O+(aq)+HS−(aq)
(2) Water as an acid:
H2O(l) +NH3(aq)⇌OH−+NH4+
(3) Self ionization of water in which water simultaneous acts as acid and base.
2H2O→H
Q 9.25. Write chemical reactions to justify that hydrogen peroxide can function as an oxidising as well as reducing agent.
A 9.25 H2O2 as an oxidising agent:
2Fe2+ (aq) + 2H+(aq) +H2O2(aq) → 2Fe3+ (aq) + 2 H2O(l)
H2O2 as a reducing agent:
I2(s) + H2O2 (aq) + 2OH– (aq) → 2I– (aq) + 2 H2O(l) + O2(g)
Q 9.26. What is meant by ‘demineralised’ water and how can it be obtained?
A 9.26 Water free from salts and minerals is called Demineralized water. Ion exchange method is used for this process. The ions present in the water bind to the positively or negatively charged sites on a resin when water is passed through the column packed with resin.
Q 9.27. Is demineralised or distilled water useful for drinking purposes? If not, how can it be made useful?
A 9.27 No, demineralised or distilled water is not fit for drinking purposes. It can be made useful by adding required amount of ions which are useful for our body.
Q 9.28. Describe the usefulness of water in biosphere and biological systems.
A 9.28 (i) Major part of all living system is made of water.
(ii) It constitutes about 65 – 70% of body weights of animals and plants.
(iii) Some properties of water like high specific heat, thermal conductivity, surface tension, high polarity allow water to play a major role in biosphere.
(iv) Because of high heat of vaporisation it is responsible to regulate temperature of living beings.
(v) It is an excellent fluid for the transportation of minerals and nutrients in plants.
(vi) It is also required for photosynthesis in plants.
Q 9.29. What properties of water make it useful as a solvent? What types of compound can it (i) dissolve, and (ii) hydrolyse?
A 9.29 Water is highly polar in nature. That is why it has high dielectric constant and high dipole moment. Because of these properties, water is a universal solvent.
Water is good solvent for ionic compounds but poor solvent for covalent compounds. It can hydrolyse ionic compounds.
Q 9.30. Knowing the properties of H2O and D2O, do you think D2O can be used for drinking purposes?
A 9.30 No, D2O is injurious to human beings, plants and animals.
Q 9.31. What is the difference between the terms ‘hydrolysis’ and ‘hydration’?
A 9.31 Hydrolysis is defined as a chemical reaction in which hydrogen and hydroxide ions (H+ and OH− ions) of water molecule react with a compound to form products. For example:
NaH+H2O → NaOH+H2
Hydration is defined as the addition of one or more water molecules to ions or molecules to form hydrated compounds. For example:
CuSO4+5H2O → CuSO4.5H2O
Q 9.32. How can saline hydrides remove traces of water from organic compounds?
A 9.32 Saline hydrides (i.e. CaH2 NaH etc.) react with water and form the corresponding metal hydroxide with the liberation of H2 gas. Thus, these hydrides can be used to remove traces of water from the organic compounds.
NaH(s) + H2O(l) → NaOH(aq) + H2(g)
CaH2(s) + 2H2O(l) → Ca(OH)2(aq) + H2(g)
Q 9.33. What do you expect the nature of hydrides is, if formed by elements of atomic numbers 15,19, 23 and 44 with dihydrogen? Compare their behaviour towards water.
A 9.33 Atomic number 15 is of phosphorus. The hydride is PH3 and its nature is covalent. Atomic number = 19 is of potassium. The hydride is KH and it is ionic in nature. Atomic number = 23 is of vanadium. The hydride is VH. It is interstitial or metallic. Atomic number =44 is of ruthenium, its hydride is interstitial or metallic.
Q 9.34. Do you expect different products in solution when aluminium (III) chloride and potassium chloride treated separately with (i) normal water (ii) acidified water, and (iii) alkaline water? Write equation wherever necessary.
- A 9.34 KCl is a salt of strong acid HCl and strong base KOH. Such salts are neutral in nature and do not undergo hydrolysis. In neutral water, acidic water, and alkaline water, KCl dissociates as Water
- KCl → K++Cl−
- AlCl3 is a salt of strong acid HCl and weak base Al(OH)3.
- (i) In normal water, it is hydrolyzed.
- AlCl3+3H2O→Al(OH)3+3H++3Cl−
- (ii) In acidic water, H+ ions react with Al(OH)3 (obtained from the hydrolysis of AlCl3) forming water and Al3+ ions. Hence it exists as Al3++Cl−
AlCl3 + acidifiedwater → Al++3Cl− - (iii) In alkaline water, the Al(OH)3 obtained from hydrolysis of AlCl3 reacts with hydroxide ions of alkali. The reaction is Al(OH)3+OH−→[Al(OH)4]−
Q 9.35. How does H2O2 behave as a bleaching agent?
A 9.35 Bleaching action of H2O2 is due to the oxidation of colouring matter by nascent oxygen.
H2O2→ H2O + O
Q 9.36. What do you understand by the terms: (i) Hydrogen economy (ii) hydrogenation (iii) ‘syngas’ (iv) water-gas shift reaction (v) fuel-cell?
A 9.36
- (i) Hydrogen economy: The basic principle of hydrogen economy is the storage and transportation of energy in the form of liquid or gaseous dihydrogen.
- (ii) Hydrogenation: Hydrogenation means addition of hydrogen across double and triple bonds in presence of catalyst to form saturated compounds.
- (iii) Syngas: The mixture of CO and H2 are called synthesis gas or ‘syngas’. It can be produced by the reaction of steam on hydrocarbon or coke at high temperature in the presence of nickel catalyst
- (iv) Water-gas shift reaction: The amount of hydrogen in the syngas can be increased by the action of CO of syngas mixture with steam in the presence of iron chromate as catalyst.This is called water-gas shift reaction.
- (v) Fuel-Cell: It is a cell which converts chemical energy of fuel directly into electrical energy.
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