UNIT# 11
HYDROGEN AND WATER
|
Q# |
Question |
Year |
|
Q# 01 |
Write Uses of hydrogen per oxide. |
[2014] |
|
Q# 02 |
Write three uses of
Hydrogen. |
[2012] [2010] |
|
Q# 03 |
Differentiate
between soft water and hard water. |
[2013] |
|
Q# 04 |
Define Soft water. |
[2019] [2010] |
|
Q# 05 |
Define
Hard water. |
[2018][2011][2010] |
|
Q# 06 |
Define heavy water. |
[2018][2010] |
|
Q# 07 |
What
are the methods of removal of hardness of water by Clerks method and Zeolite
Permutitt? |
[2013]
[2015] [2011] |
|
Q# 08 |
Difference between ordinary
water and heavy water. |
[2017] [2015] |
|
Q# 09 |
What
causes the permanent hardness? |
[2018] |
|
Q# 10 |
Define crystallization;
write names and chemical formulae of two hydrated salts. |
[2014] |
|
Q# 11 |
Write
chemical reaction of water with the following elements with balanced chemical
equations: ·
Magnesium ·
Chlorine ·
Silicon |
[2010] |
Q. Write few lines on Hydrogen.
INTRODUCTION
TO HYDROGEN
Cavendish discovered the
hydrogen in the year 1766 by the action of zinc metal over dilute hydrochloric
acid.
Zn + 2 HCl ⟶ ZnCl2 + H2
In Greek, hydro
means ‘water’ and ‘genan’ means ‘producer’.
So, Hydrogen means ‘water producers’.
Hydrogen is the lightest
element known. It exists in diatomic molecular gas.
Q. Describe the occurrence of
Hydrogen.
OCCURRENCE
OF HYDROGEN
1. Hydrogen is one of the most
abundant elements in the universe.
2. About 70% of the universe is
composed of hydrogen.
3. The sun and the stars are
largely composed of hydrogen.
4. It is mostly found in the
combined state of water (H2O).
5. Hydrogen is present in the water
11.11% by mass is oxygen.
6. In the earth crest, hydrogen
is the 9th most abundant element.
Q. Describe industrial
preparation of Hydrogen.
INDUSTRIAL
PREPARATION OF HYDROGEN
1) From Natural Gas (Hydrocarbon
– Steam Process)
Natural gas contains methane (CH4)
is partially oxidized by the steam at about 10000C in the presence
of Nickel catalyst.
CH4 + H2O
® CO + 3H2
2) By the electrolysis of water
Hydrogen gas can be prepared
by the electrolysis of water. When electric current is passed through the water
in the presence of few drops of acid or base, H2 gas is liberated at
the cathode and O2 gas as a by-product collects at anode.
2H2O ® 2H2 + O2
3) By the thermal decomposition
of methane
When methane is heated above
7000 C in the absence of air, CH4 decomposes thermally to
produce Carbon black and H2 gas.
CH4 ® C
+ 2H2
4) By passing steam over coke (Coke
steam process)
When steam is passed over red
hot coke at about 10000 C, a mixture of CO and H2 called
water gas is produced.
C + H2O ® CO
+ H2 [Mixture
of H2 & CO is called water gas]
Water gas is used in the
preparation of methanol (methyl alcohol).
Q. Describe method of separation
of Hydrogen from water gas.
SEPARATION OF HYDROGEN FROM
WATER GAS
From water gas, H2
gas can be separated by two methods.
i.
Liquefaction
ii.
Oxidation
OXIDATION
(BOSCH PROCESS)
In this process, more steam
is passed though the water gas at 5000C in the presence of iron
oxide (FeO) OR chromium oxide (Cr2O3) catalyst.
CO gas in H2O
oxidizes to the CO2 gas which is soluble in water under pressure liberating
pure H2 gas.
CO + H2 +H2O ® CO2
+ 2H2
LIQUEFACATION
When water gas is cooled up
to -2000 C, CO liquefies and leaving behind H2 gas. Traces
of CO gas if left in the mixture then it is treated with the caustic soda
(NaOH). As a result, pure H2 gas is released.
CO + NaOH ® HCOONa
Q. Describe Physical properties
of Hydrogen.
PHYSICAL
PROPERTIES OF HYDROGEN
1. It is colorless, odorless and
tasteless gas.
2. It is highly inflammable gas
and burns with the blue flame.
3. It is absorbs on the surface
of the some metals and makes the surface spongy.
4. Its electro negativity is 2.1.
5. Its ionization energy is
13.54 electron volt (eV).
6. It liquefies at -252 0C.
7. It solidifies at -2590C.
8. It is insoluble in water.
Q. Describe Chemical properties
of Hydrogen.
CHEMICAL
PROPERTIES OF HYDROGEN
1)
Decomposition of molecular hydrogen (H2)
Molecular hydrogen contains
stable covalent bonding and is relatively inert at ordinary conditions. Its bond
dissociation energy is 104 K cal.
H-H ® H+ H
2) As a reducing agent
Hydrogen shows greater
affinity for oxygen and reduces many metals oxides into free metals.
CuO + H2 ® Cu
+ H2O
WO3 + 3H2 ® W +
3H2O
3) Reactions with metals
Alkali metals like Na, K etc.
and alkaline earth metals like Ca, Ba react with H2 to form ionic hydrides.
2Na + H2 ® 2NaH
Ca + H2 ® CaH2
4) Reaction with non-metals
Hydrogen reacts with non-metals
under different conditions to form addition products
2H2 + O2 ® 2H2O
N2 + 3H2 ® 2NH3
H2 + Cl2 ® 2HCl
H2 + S ® H2S
5) Hydrogenation reaction
The addition of hydrogen into
other molecular compound is called hydrogenation reaction. When molecular
compounds and hydrogen are heated in the presence of Pt/ Pd give addition
products.
CO + 2H2 ® CH3
– OH
CH2 = CH2
+ H2 ® CH3 – CH3
Q. Describe Uses of Hydrogen.
USES
OF HYDROGEN
1. Hydrogen is used in the
manufacture of fertilizers.
2. It is used in the
manufactures of vegetable ghee from edible oils.
3. It is used for the
purification of metals.
4. It is used in the manufacture
of tungsten bulb filaments.
5. It is used in the weather
balloons.
6. It is used in the preparation
of chemicals like NH3, CH3OH etc.
7. It is used as a fuel in the
form of water gas.
Q. Write short note on Nascent
Hydrogen.
NASCENT HYDROGEN
Chemically,
the newborn hydrogen is more reactive than the molecular hydrogen. As because
at the time of birth it occurs in atomic form. Such hydrogen is known as
Nascent hydrogen.
FeCl3
+ H2 ® No
reaction
FeCl3 +
[H] ® FeCl2 + HCl
Q. What is Isotopes? Write note
on Isotopes of Hydrogen.
ISOTOPES
Those elements which have
same charge number but different mass number are called Isotopes.
OR
Atoms
of an element having same number of protons but different number of neutrons
are called isotopes.
ISOTPOES OF HYDROGEN
There are three isotopes of
hydrogen.
1. Protium
2. Deuterium
3. Tritium
PROTIUM
It has one proton and no
neutron in the nucleus.
Its atomic number is 1 and
mass number is also 1.
It is used in ordinary water.
DEUTRIUM
It has one proton and one
neutron in the nucleus.
Its atomic number is 1 and
mass number is 2.
It is used in heavy water.
TRITIUM
It has one proton and two
neutrons in the nucleus.
Its atomic number is 1 and
mass number is 3.
It is used in crackers. It is
also known as radioactive isotope of Hydrogen.
Q. What do you know about water?
WATER
Water
is colorless, odorless and tasteless liquid. Its freezing point is 0oC
and it boils at 100oC.
Q. Describe chemical properties
of Water.
CHEMICAL
PROPERTIES OF WATER
1)
REACTION OF WATER WITH METALS
Water
reacts with metals in number of ways.
·
With More Electropositive
Metals
Sodium,
potassium and calcium etc. react with the cold water to form their hydroxides
with the liberation of H2 gas.
2Na
+ 2H2O ® 2NaOH + H2
2K
+ 2H2O ® 2KOH + H2
Ca
+ 2H2O ® Ca(OH)2 + H2
·
With Less Electropositive
Metals
Reaction
of water with the less electro positive metals results in the formation of
oxides and liberation of H2 gas
Mg
+ H2O ® MgO + H2
Zn
+ H2O ® ZnO + H2
3Fe
+ 4H2O ® Fe3O4
+ 4H2
2) REACTION OF WATER WITH NON METALS
Chlorine
reacts with water to produce hydrochloric acid and hypochlorous acid.
Cl2
+ H2O ® HCl + HClO
HClO
® HCl
+ [O]
C +
H2O ® CO + H2
Si
+ 2H2O ® SiO2 + 2H2
3) ACTION WITH CALCIUM OXIDE [QUICK LIME]
CaO
+ H2O ® Ca(OH)2
Q. Define Soft water, hard water
and heavy water.
SOFT
WATER
The surface water which contains low concentrations of calcium and
magnesium ions is called Soft water.
HARD
WATER
The water which contains high mineral content in contrast to soft water
is called Hard water. It is usually formed by the percolation of water through
the deposition of limestone and chalk [which are in high contents of calcium
and magnesium carbonates]
HEAVY
WATER
The water in which the hydrogen in the molecules is partially or
completely replaced by the isotope deuterium is called Heavy water. It is used
especially as a moderator in nuclear reactors. The chemical formula of D2O.
Q. Describe the causes of
Hardness of water.
CAUSES
OF HARDNESS
As
the rain water falls to the ground, CO2 from the atmosphere
dissolves in it. Moreover, due to floating of this water across the soil and
rocks, Ca and Mg also gets dissolved in it. These changes in the molecular
structure of water results in the hardness of water; if certain changes are
soluble in water, thus named as Temporary hardness.
CaCO3
+ CO2 + H2O ⟶ Ca(HCO3)2
MgCO3
+ CO2 + H2O ⟶ Mg(HCO3)2
Q. Describe the types of Hardness
of water.
TYPES
OF HARDNESS
There
are two types of hardness in water:
·
Temporary Hardness
·
Permanent hardness
TEMPORARY
HARDNESS
Temporary
hardness is usually caused by the addition of dissolved salts of hydro carbonate
of calcium and magnesium.
Ca(HCO3)2 ⟶ Ca+2 + 2HCO3-1
Mg(HCO3)2
⟶ Mg+2
+ 2HCO3-1
PERMANENT
HARDNESS
Permanent
hardness is due to dissolved chloride and sulphates of Ca and Mg
CaCl2
⟶ Ca+2 + 2Cl-1
MgCl2 ⟶ Mg+2
+ 2Cl-1
Q. Describe the methods of
removal of Hardness of water.
METHODS
OF REMOVAL OF HARDNESS
TEMPORARY
HARDNESS REMOVAL METHODS
Hardness
of water can be removed by the applications of the following methods:
· By Heating
Significantly,
the simplest method of removal of hardness of Ca and Mg salts is boiling which
results in the elimination of water.
Ca(HCO3)2
⟶ CaCO3
+ CO2 + H2O
· Clark’s method
This
method was proposed by Clark, thus named as Clark’s method. In this method,
water is treated with the slaked lime to convert the hydrogen carbonates of Ca
and Mg into their insoluble carbonates. Contrary, the soft water is drained off
for the use.
Ca(HCO3)2
+ Ca(OH)2 ⟶ 2 CaCO3
+ 2H2O
Mg(HCO3)2
+ Ca(OH)2 ⟶ MgCO3 + CaCO3 + 2H2O
PERMANENT
HARDNESS REMOVAL METHODS
· By using washing soda (Na2CO3.
10H2O)
When
washing soda is added to the permanent hard water, insoluble CaCO3
MgCO3 are precipitated from the soluble salts of Ca and Mg
CaSO4 + Na2CO3 ⟶ CaCO3
+ 2Na2SO4
MgCl2 + Na2CO3 ⟶ MgCO3
+ 2NaCl
· By using Caustic soda
The
treatment of permanent hard water with caustic soda results in formation of
precipitate
MgSO4
+ 2NaOH ⟶ Mg(OH)2 +
Na2SO4
· By using Permutit OR Zeolite
CaSO4
+ Na-zeolite ⟶ Ca-zeolite + Na2SO4
Ca-zeolite
+ 2NaCl ⟶ Na-zeolite + CaCl2
Q. Define Crystallization. Name
some rehydrated salts.
CRYSTALLIZATION
Crystallization is the
solid-liquid separation and purification procedure in which mass transfer
occurs from the liquid solution to a pure solid crystalline phase.
HYDRATED
SALTS
·
CuSO4. 5H2O
·
FeSO4. 7H2O
·
Na2CO3.
10H2O
·
AlCl3. 6H2O
·
BaCl2 . 2H2O
Q. Describe classification of
water pollutants.
CLASSIFICATION
OF WATER POLLUTANTS
There are various types of
water pollutant can be classified into different categories.
1. Oxygen demanding waste
2. Diseases causing waste
(Micro- organism)
3. Agriculture water pollutants
OXYGEN
DEMANDING WASTE
It includes:
1. Domestic and animals sewage
2. Bio-degradable organic waste
3. Industrial waste
4. Waste from slaughter hours
5. Wastes from packing plants
All these waste undergo
degradation due to which there is rapid deletion of demand oxygen (D.O).
Demand oxygen from water is
harm full to aquatic animals.
SYNTHETIC
ORGANIC COMPOUNDS
There are the man made
materials
1. Food additives.
2. Synthetic detergent.
3. Insecticides.
4. Paints.
5. Solvent.
These materials are
potentially toxic to plants, animals, humans.
DISEASE
CAUSING WASTE
Disease causing waste
includes pathogenic micro-organism. There micro-organism may enter the water
along with sewage and other wastes. These micro-organisms compromising mainly
of virus and bacteria cause.
1. Typhoid
2. Polio
3. Cholera
4. Dysentery
5. Infectious hepatitis.
AGRICULTURAL
WATER POLLULANTS
In modern agriculture,
pesticides fertilization and organic waste and some inorganic minerals, they
become a cause of collection.
Q. What is Potable water?
Describe the characteristics of Potable water.
POTABLE
WATER
The water which is fit for
drinking purpose is called potable water. It is free from all sorts of
pollutants.
CHARACTERISTICS
1. It is colorless, odorless and
tasteless.
2. It must be free from all
types of micro-organism.
3. It should not stain the
clothes.
4. It must be free from
corrosive substance
Multiple Choice Questions
Choose the correct option for each of the
following statement.
i.
Deuterium is present in the
natural hydrogen in the ratio of:
a.
1:1200
b. 1:15000
c.
100:60000
d. 1:18000
ii.
The electronegativity of
Hydrogen is:
a.
2.1
b.
2.5
c.
2.9
d.
7.0
iii.
Human being consume water
about liters per day.
a.
1
b.
2
c.
5
d.
7
iv.
Molecular mass of heavy water
is:
a.
16
b.
18
c.
20
d.
36
v.
It is the newly born
Hydrogen:
a.
Atomic hydrogen
b.
Nascent hydrogen
c.
Molecular hydrogen
d.
Both a and b
vi.
It is radioactive isotope of
Hydrogen.
a.
Protium
b.
Deuterium
c.
Tritium
d.
Both b and c
vii.
Potable water is:
a.
Fit for chemical
reaction
b.
Fit for drinking
c. Fit pollution
d. Unfit for health
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