EXERCISES
9.1 Justify the position of hydrogen in the periodic table on the basis of its electronicconfiguration.
9.1 Justify the position of hydrogen in the periodic table on the basis of its electronicconfiguration.
9.2 Write the names of isotopes of hydrogen. What is the mass
ratio of these isotopes?
9.3 Why does hydrogen occur in a diatomic form rather than in a
monoatomic form
under normal conditions?
9.4 How can the production of dihydrogen, obtained from ‘coal
gasification’, be
increased?
9.5 Describe the bulk preparation of dihydrogen by electrolytic
method. What is the
role of an electrolyte in this process ?
9.6 Complete the following reactions:
(i) H2 (g ) + MmOo (s) ⎯⎯Ä⎯→
(ii) ( ) ( ) 2 catalyst CO g + H g ⎯⎯⎯Ä ⎯→
HYDROGEN 289
(iii) ( ) ( ) 3 8 2 catalyst C H g + 3H O g ⎯⎯⎯Ä ⎯→
(iv) Zn(s) + NaOH(aq) ⎯⎯he⎯at⎯→
9.7 Discuss the consequences of high enthalpy of H–H bond in
terms of chemical
reactivity of dihydrogen.
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.
9.9 What characteristics do you expect from an
electron-deficient hydride with respect
to its structure and chemical reactions?
9.10 Do you expect the carbon hydrides of the type (CnH2n + 2)
to act as ‘Lewis’ acid or
base? Justify your answer.
9.11 What do you understand by the term “non-stoichiometric
hydrides”? Do you
expect this type of the hydrides to be formed by alkali metals?
Justify your answer.
9.12 How do you expect the metallic hydrides to be useful for
hydrogen storage?
Explain.
9.13 How does the atomic hydrogen or oxy-hydrogen torch function
for cutting and
welding purposes ? Explain.
9.14 Among NH3, H2O and HF, which would you expect to have
highest magnitude of
hydrogen bonding and why?
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.
9.16 Arrange the following
(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.
9.17 Compare the structures of H2O and H2O2.
9.18 What do you understand by the term ’auto-protolysis’ of
water? What is its
significance?
9.19 Consider the reaction of water with F2 and suggest, in
terms of oxidation and
reduction, which species are oxidised/reduced.
9.20 Complete the following chemical reactions.
(i) ( ) ( ) 2 2 PbS s + H O aq →
(ii) – ( ) ( )
4 2 2 MnO aq + H O aq →
(iii) ( ) ( ) 2 CaO s + H O g →
(v) ( ) ( ) 3 2 AlCl g + H O l →
(vi) ( ) ( ) 3 2 2 Ca N s + H O l →
Classify the above into (a) hydrolysis, (b) redox and (c)
hydration reactions.
9.21 Describe the structure of the common form of ice.
9.22 What causes the temporary and permanent hardness of water ?
9.23 Discuss the principle and method of softening of hard water
by synthetic ionexchange
resins.
9.24 Write chemical reactions to show the amphoteric nature of
water.
9.25 Write chemical reactions to justify that hydrogen peroxide
can function as an
oxidising as well as reducing agent.
9.26 What is meant by ‘demineralised’ water and how can it be
obtained ?
9.27 Is demineralised or distilled water useful for drinking
purposes? If not, how can
it be made useful?
9.28 Describe the usefulness of water in biosphere and
biological systems.
9.29 What properties of water make it useful as a solvent? What
types of compound
can it (i) dissolve, and (ii) hydrolyse ?
9.30 Knowing the properties of H2O and D2O, do you think that D2O
can be used for drinking purposes?
9.31 What is the difference between the terms ‘hydrolysis’ and ‘hydration’
?
9.32 How can saline hydrides remove traces of water from organic
compounds?
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.
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 equations wherever necessary.
9.35 How does H2O2 behave as a bleaching agent?
9.36 What do you understand by the terms:
(i) hydrogen economy (ii) hydrogenation (iii) ‘syngas’ (iv)
water-gas shift reaction
(v)
fuel-cell ?