Hydrogen, Oxygen and Water
Chemistry of Non-Metals
9.1
Hydrogen
Ø
Discovered by Henry Cavendish (1776) by
passing steam through iron.
Ø
Named inflammable air, then.
Ø
Later Lavoisier named it hydrogen as it
produced water when burnt.
Ø
Lightest element, the most abundant
element in the known universe.
Symbol: H Molecular formula: H2
Atomic
number: 1 Atomic
mass: 1.008 amu
Atomic
radius: 0.37 Ao Ionic
radius (H-): 2.1 Ao
Ionization energy: 1310 KJ mol-1 Electronegativity: 2.1
9.1.1 Chemistry of atomic and nascent
hydrogen
Atomic
hydrogen
Ø Generally
produced by passing molecular hydrogen through
an electric arc between two tungsten electrodes at about 30000C.
Ø
Strong
reducing agent more powerful than nascent hydrogen;
can reduce oxides and chlorides of metals like silver, mercury, copper and
lead.
It can reduce BaSO4 to BaS and CO to
formaldehyde (Methanal).
Uses of atomic hydrogen:
·
As
reducing agent
·
As
atomic hydrogen torch for welding metals of very high melting points.
Nascent Hydrogen
Ø Hydrogen formed by a chemical reaction at the moment
of its origin or Newly formed hydrogen in situ.
Ø Ordinary
molecular hydrogen gas, when passed through acidified KMnO4, K2Cr2O7
& FeCl3 solutions separately doesn’t reduce them.
Ø
But nascent hydrogen produced in situ,
in the medium itself containing the oxidizing agents, reduces them. This shows
nascent hydrogen is a more powerful reducing agent than ordinary hydrogen gas.
Ø
Earlier assumed that nascent hydrogen
is the atomic hydrogen.
Ø
But at present, it is thought that a
part of the heat change of the chemical reaction is imparted to the hydrogen in
situ, making it more energetic.
Ø The
internal pressure of the tiny bubbles formed in the solution also contributes
to its higher reactivity.
Uses of nascent hydrogen:
·
As
a reducing agent.
1. Distinguish
between nascent and atomic hydrogen. 2
|
Nascent
Hydrogen |
Atomic
Hydrogen |
|
Can be produced at ordinary temperature by reaction
between acid, alkali, alcohols or water with reactive metals. |
Can be produced only at high temperatures (about
30000C) by the dissociation of H2 molecules
at low pressure. |
|
Couldn’t be isolated. |
Could be isolated. |
|
Relatively less powerful reducing
agent. |
More powerful reducing agent. |
2. What
is nascent hydrogen? Show that nascent hydrogen is a more powerful reducing
agent than molecular hydrogen. 2
3. Mention
one important use of nascent hydrogen. 1
4.
Illustrate with
an example that nascent hydrogen is a more powerful reducing agent than
dihydrogen. 2
5.
Give a reaction
to show that nascent hydrogen is a more powerful reducing agent than molecular
hydrogen. 2
6.
What happens
when zinc dust is added to an acidified solution of potassium permanganate? 2
9.1.2 Isotopes
of hydrogen and their uses
|
|
|
1p 2n |
|
1p 1n |
|
1p |
Protium,
1H1, Deuterium, 1H2,
D, Tritium,
1H3
These isomers
differ from one another in the number of neutrons in the nucleus as shown
above. Protium does not have any neutrons. Deuterium has 1 neutron and tritium
has 2 neutrons in the nucleus. Their mass numbers are 1, 2 and 3 respectively.
The three isotopes
have the same atomic number and
electronic configuration. Hence they have the same chemical properties.
Due to the different atomic masses, their physical properties
and rate of reactions differ.
The relative abundances
of protium, deuterium and tritium are 99.985 %, 0.015 % and 10-15 %
respectively.
7. Write
short notes on isotopes of hydrogen. 3
8.
In what respect
do the isotopes of hydrogen differ from one another? 1
9.
List all the
possible isotopes of hydrogen. 1
10.
Mention the most
abundant isotope of hydrogen. 0.5
11.
Which is the
least abundant isotope of hydrogen? 0.5
12.
Name the
isotope which does not contain a neutron. 0.5
Uses of Hydrogen (or Protium)
·
In the industrial synthesis of
ammonia by Haber’s process.
·
In the hydrogenation of vegetable oil
into vegetable ghee (margarine).
·
In filling balloons and airships
·
In metallurgical processes as a reducing
agent.
·
In rockets and missiles as a fuel.
·
Hydrogen could be used as our future
fuel, without polluting the environment, if water could be decomposed
economically by using solar or other renewable energy.
13. Mention
an important use of Dihydrogen. 1
Uses
of Heavy hydrogen (deuterium)
·
As a tracer in the study of the reaction
mechanism.
·
In the transformation of elements (i.e.,
nuclear reactions to transform one element into another)
14. Mention
one important use of heavy hydrogen. 1
15.
Mention an
important use of deuterium. 0.5
Uses
of Tritium (Radioactive
isotope)
·
As a radioactive tracer in biology,
chemistry, medicine etc.
·
In nuclear reactions to produce energy.
·
In exit signs in dark halls.
16.
Mention an important use of tritium. 0.5
17. Which
of the isotope of hydrogen is radioactive? 1
9.1.3 Application of hydrogen as fuel
Because of high inflammability, pollution-free combustion
and high enthalpy of combustion of hydrogen, it is used as a fuel and
considered a very potential future fuel. It can be used in fuel
cells and internal combustion engines.
A wide variety of
research is being conducted currently on this topic.
Hydrogen is currently used in rockets and missiles as fuel.
It
could be used as our future fuel, without polluting the environment, if water
could be decomposed economically by using solar or other renewable energy.
Advantages of hydrogen as a fuel:
·
High energy efficiency
·
Mitigation of
greenhouse gases (green fuel)
·
Reduction of
petroleum use
·
Reduction of
air pollution
·
Zero carbon
emission
Challenges in the use of hydrogen as a fuel
·
High cost of hydrogen, its storage,
transportation and distribution technology.
·
Takes more space to store in the fuel
tank
·
Difficult to store in the high-pressure
tank or cryogenic tank.
9.1.4 Heavy water
and its applications
Deuterated water (D2O or 1H22O)
or deuterium oxide is called heavy water. It is obtained in residual water
after electrolysis of a large amount of water. This is employed
·
In the preparation of heavy hydrogen
(deuterium, D2).
·
As a moderator in nuclear reactors to
slow down the fast-moving neutrons.
18. What
is meant by heavy water? Mention it’s any two applications. 2
19.
Mention one
important use of deuterated water. 0.5
20.
Mention one
important use of heavy water. 1
- Which of
the following is the most reactive form of hydrogen
a. Nascent
hydrogen c. Atomic
hydrogen
b. Ortho hydrogen d. Para hydrogen
- When a
piece of zinc metal is added to acidified potassium permanganate solution,
the colour changes into
a.
Pink b.
Orange c. Green d. Colourless
3.
Which has one proton and one neutron?
a.
2He4 b.
H2 c.
1T3 d.
1D2
4.
Which of the followings are isotopes of hydrogen?
a.
Atomic hydrogen and nascent hydrogen
b.
Protium, deuterium and tritium
c.
Molecular hydrogen and atomic hydrogen
d.
Atomic hydrogen and heavy hydrogen
- Which of
the following is known as heavy hydrogen?
a.
Protium c.
Deuterium
b.
Tritium d.
Ortho hydrogen
- The
composition of the nucleus of deuterium is
a. one electron,
one proton c. one proton, one
neutron
b. one neutron,
one electron d. two protons, one
electron
- Which of
the following is known as radioactive hydrogen?
a.
Protium b.
Deuterium c. Tritium d. Ortho hydrogen
- Tritium is
an isotope of
a. Tellurium b. Titanium c. Hydrogen d.
Tantalum
9.
Naturally occurring hydrogen contains maximum proportions of
a.
Protium b.
deuterium c. tritium d. heavy hydrogen
10.
Heavy water is
a.
D2O b.
H2O c. T2O d. H2 + CO
- Heavy
water is obtained by
a.
Prolong electrolysis of water d. Distillation of water
b.
Dissolving heavy salt in water
c.
Removing impurities of Calcium and Magnesium in water.
- Heavy
water is used as
a.
Drinking water c.
washing water
b.
Blood purifier d.
moderator
- Heavy water
is used in atomic reactors as
a.
Coolant c.
Both coolant and moderator
b.
Moderator d. Neither coolant nor moderator
9.2
Oxygen
·
Discovered by Joseph Priestly in 1772
and Sceelee in 1773.
·
Named by Antoine Lavoisier after its
detailed study.
·
3rd most abundant element in
the earth’s crust & the human body.
Atomic number: 8 Atomic
mass: 15.999amu
Molecular mass (O2): 32 Valency:
2
Oxidation number: -2 (-1 in peroxide
and -1/2 in superoxide)
Electronegativity: 3.5 (2nd
most electronegative element after F)
Ionization energy or IP: 1317KJ/mol
·
Oxygen has 3 isotopes 8O16,
8O17, 8O18, their relative
abundances are 99.76%, 0.03% and 0.204% respectively.
The property by virtue of which an element exists
in different forms with different physical properties and the same chemical
properties is called allotropy.
Such different forms of the same element are called allotropes.
Oxygen shows
allotropy. Oxygen (O2) and ozone (O3) are allotropes.
21. Name
the allotropes of oxygen. 1
22.
Mention one example
of an allotrope of oxygen. 0.5
9.2.2 Types of
oxides
Binary
compounds of other elements with oxygen are called oxides. These can
be classified on different basis as discussed below.
·
Classification
on the basis of acidic or basic behaviour
a) Basic
oxides
The
oxides that form a base on combination with water are called basic oxides.
Generally, metal oxides are basic. e.g.
The basic oxides react with acid to form salt and water.
b) Acidic
oxides
The oxides that form acid on combination with water are
called acidic oxides. Generally, oxides of non-metal are acidic. E.g.
Acidic oxides react with bases to form salt and water.
c) Neutral
oxides
Neutral oxides do not react with an
acid or a base to form salt e.g., NO, CO, H2O, N2O etc.
d) Amphoteric
oxides
These are oxides that react with acids as well as bases to
form salts. Oxides of Al, Zn, Sn and Pb are
amphoteric oxides.
ØAs
we move from the left to right in the periodic table, the behaviour of the
oxides gradually changes from basic to amphoteric then acidic.
|
Na2O, MgO, Al2O3, SiO2, P2O5, SO3, Cl2O7 basic amphoteric acidic strongly
acidic |
·
Classification
of oxides based on structure
a) Peroxides
These oxides contain the group (-O-O-)2-,
in which the oxidation number of oxygen is -1. E.g. H2O2,
Na2O2, BaO2, R-O-O-R (ROOR) etc.
b)
Mixed oxides
These oxides behave as if they were the mixtures of two
simpler oxides of the same element.
e.g. Fe3O4
(FeO + Fe2O3) - ferroso ferric oxide, Pb3O4 (PbO+PbO2)
23. What
are oxides? 1
24. Write
an example of mixed oxide. 0.5
25. Write
an example of amphoteric oxide. 0.5
26. Write
the names of any two neutral oxides with their formulae. 2
27. Mention
one example of Peroxide 1
28. What
are Neutral and Amphoteric oxides? Give 1 example of each. 2
29. Give reason: a) CO2 is an acidic oxide.
b) Al2O3 is an amphoteric oxide.
30.
Classify the
following oxides with reason: Al2O3, CO2 2
31. Classify
the following oxides justifying the classification:
a) NO b) CO2
c) ZnO d) CaO 1
32. Choose
oxide from the following that you would expect to be acidic. Give reactions to
justify your choice. Na2O, ZnO, MgO, and SO3. 2
33.
Give reason
to show a) Al2O3 is an amphoteric oxide b) BaO2
is peroxide.
34.
Classify the
following oxides giving a suitable reason:
i) BaO2 ii) Al2O3
35. Classify
the following oxides: N2O3, NO, BaO2,
Fe2O3 2
36. Classify the following oxides: BaO2, Al2O3,
Fe3O4, N2O3 2
9.2.3 Applications
of hydrogen peroxide
Ø One of the common peroxides with
molecular formula H2O2.
Ø Clear liquid with disinfectant,
antiviral and antibacterial activities.
Applications
·
As
an oxidising agent in laboratories and many industries
·
As
a mild bleaching agent for silk, wool, pulp, paper etc.
·
As
antiseptic, to clean wounds & in some sanitisers also
·
To
prepare mouthwash (for dental hygiene - due to antiseptic properties)
·
As
propellant in rockets
·
To
produce organic peroxides(ROOR), some of which are explosives too
9.2.4 Medical and
industrial application of oxygen
It is the most
essential element for life on earth. Apart from being used in respiration and
combustion. It is used in
-
Artificial respiration in hospitals
All living cells need a constant supply of oxygen for
aerobic respiration. It is used by the cells to oxidise the food to produce
energy.
Lack of oxygen for a few minutes leads to cell death.
Therefore in a wide variety of medical conditions (hypoxemia, chronic
obstructive pulmonary disease, pneumonia, heart attack, respiratory diseases,
during surgeries etc.), oxygen should be given to the patients.
-
Mountaineering, diving and space travelling.
-
Manufacture of steel
-
Oxy-hydrogen and oxy-acetylene flame in
the cutting and welding of metals.
-
As an oxidising and bleaching agent.
-
Fuel for rockets and missiles.
14.
The most abundant element on the earth’s surface is
a.
Oxygen b.
Silicon c. Aluminium d. Iron
15.
Oxygen and ozone are regarded as
a.
Allotropes b.
isotopes c. isomers d. isobars
16.
Which of the following is acidic oxide?
a.
SiO2 b.
Al2O3 c.
SnO2 d.
PbO2
- Which of
the following is basic oxide?
a.
Copper oxide c.
Silicon oxide b. Calcium oxide d. Both (a) and (b)
- Which of
the following would form basic oxide?
a.
Sulphur b. Carbon c. Silicon d. Calcium
- Which of
the following is amphoteric oxide?
a.
H2O b.
CaO c. Al2O3 d. Cl2O7
- Which of
the following is amphoteric oxide?
a.
SnO b. BaO c. BaO2 d. Mn3O4
- Which of
the following is not an amphoteric oxide?
a.
PbO b. ZnO c. MgO d. Al2O3
- Which of
the following oxides reacts with both HCl and NaOH?
a.
ZnO b. CO c. P2O5 d. N2O
- Which of
the following is the most acidic oxide?
a.
Na2O b.
MgO c. P2O5 d. SO3
- Which of
the following is peroxide?
a.
KO2 b.
K2O c.
BaO2 d.
Pb3O4
- The
electronic configuration of an element is 2, 8, 1. Which of the following
statements is true?
a.
It is diatomic. c.
It is a nonmetal.
b.
It is a transition metal. d.
It forms basic oxide.
Ozone
9.3.1 Occurrence
The
ozone layer lies in the stratosphere, 12 to 24 km from the surface of the
earth. Ozone is naturally formed in the stratosphere as O2 molecules
absorb the high-energy ultraviolet rays of the sun. UV radiation splits O2
molecules into oxygen atoms that combine with oxygen molecules to form ozone.
37. How
does the formation of ozone take place in the stratosphere? 2
38.
How is ozone
formed in the stratosphere? 1
39. What
is the ozone layer? 2
40. How
does ozone protect plant and animal life on earth? 1.5
9.3.2 Preparation of ozone from oxygen
It
is prepared in the laboratory by passing silent electric discharge (i.e.
without any spark) or ultraviolet radiation in a spherically designed
instrument called an ozonizer. It is an endothermic reaction.
9.3.3 Structure of ozone
It has been established that the ozone molecule has an
angular shape.
Its structure may be
represented by a resonance hybrid of the following two Lewis dot structures.
But it is found to have a dipole moment of 0.53D. Hence its
structure may be represented as:
41. Give
resonance structure of ozone. 2
9.3.4 Test for
ozone
Test
of ozone may be based on one of its following properties.
1. It
is a pale blue gas with a distinctively pungent fishy smell.
2.
When ozone is passed into a
mixture of KI solution and starch solution, blue colouration appears. The
involved reaction may be shown as;
3. Tailing
of mercury test: Mercury does not stick to the glass surface. However, when
exposed to the atmosphere of ozone, it loses its meniscus and sticks to the
glass surface. This is due to the formation of mercurous oxide as shown below.
42. What
happens when Mercury is exposed to an ozonized atmosphere?
43. What
is meant by the tailing of mercury? 2
9.3.5 Ozone
layer depletion (causes, effects and control measures)
(Study from books)
44. How
does CFC (Chlorofluorocarbons) deplete the Ozone layer? 2
45. What
is meant by ozone hole? 2
46. Name
any one gas responsible for the depletion of the ozone layer of the upper part
of our atmosphere. Why is it harmful to living beings, if the ozone layer gets
depleted? 2
47. Suggest
your ideas to protect the Ozone layer from its depletion. 2
48.
Why do you
think depletion of the ozone layer from the atmosphere will be harmful to
plants and animal life? 2
49.
Mention one
important use of the ozone layer. 0.5
9.3.6 Uses of
ozone
1. As
a germicide and as a disinfectant for sterilising water and improving the
atmosphere of crowded places.
2. As
an oxidising agent.
3. In
the ozonolysis of unsaturated hydrocarbons.
4. For
bleaching oils, ivory articles and other soft materials.
5.
For the manufacture of potassium permanganate
(KMnO4), a very useful compound, from potassium manganate.
50.
Give any two
uses of ozone. 1
51. Give one important use of
ozone. 1
26.
Ozone is
a.
A compound of oxygen c.
An isotope of oxygen
b.
An isomer of oxygen d.
An allotrope of oxygen
27.
Ozone is in high concentration in
a.
Troposphere b. Stratosphere c. Mesosphere d. Thermosphere
- Ozone is
formed in the upper layer of the atmosphere by
a.
Combination of O2 d.
The action of UV rays on O2
b.
High pressure on O2
c.
The action of electric discharge on O2
29.
The ozone layer protects us from
a.
Ultraviolet radiation c.
Infra-red light from the Sun
b.
Visible light from the sun d.
X-ray from the sun
- The ozone
layer in the stratosphere is depleted by
a.
SO2 b.
CO2 c.
Freons d. N2
- Freon is
a.
CF2Cl2 b.
CCl4 c.
CF4 d.
CHCl3
- Ozone hole
in the stratosphere is mainly due to
a.
Chloroform c.
Tetrachloromethane
b.
Carbon dioxide d.
chlorofluorocarbon
- The main
species produced by CFCs to deplete the ozone layer is
a.
O. b. Cl. c. Cl2 d. O2
- Which of
the following statements is true about the ozone layer?
a.
It is harmful because ozone is dangerous to the living
organisms.
b.
It is beneficial because oxidation reactions can proceed
faster in the presence of ozone.
c.
It is beneficial because ozone cuts the ultraviolet
radiation of the sun.
d.
It is harmful because ozone cuts out the important radiation
of the sun which is vital for photosynthesis.
- One
molecule of CFC can destroy up to … molecules of ozone.
a.
100 b.
1000 c. 10000 d. 100000
36.
The structure of ozone molecule is
a.
Triangular b.
Trigonal c. Bent d. Linear
37.
Ozone is
a.
Colourless gas c.
Pale green gas
b.
Pale blue gas d.
Pale yellow gas
- Tailing of
mercury is caused by
a.
O2 b.
Cl2 c.
O3 d.
N2
39.
Ozone is used to purify
a.
Sugar solution c.
Ethyl alcohol
b.
Water d.
Acetic acid
- The gas
used in sterilising water is
a.
Oxygen b.
Ozone c. Hydrogen d. Nitrogen
- Ozone can
act as
a.
Oxidising agent c.
Germicide
b.
Disinfectant d.
Oxidising, germicide and disinfectant
- The bleaching
action of ozone is due to
a.
Oxidation b. Reduction c. Both d.
None
NaCl is
dissolved in water, then the Na+ ion is
- Hydrolysed c.
Hydrated
- Oxidised d.
Reduced (IOM 2016)
*** This is not a complete note. It is just to guide
you. It is recommended to study prescribed textbooks along with this material.
***
Labels: Chemistry class 11 NEB, chemistry notes, concise and comprehensive, Inorganic chemistry, nonmetals
posted by Subarnam Oli @ March 23, 2023
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