Hydrogen gas

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30th April 2012
Hydrogen gas
Industrial preparation
a) Electrolysis of acidulated water
Water is acidified with sulphuric acid to conduct electricity. Heavy current is passed
through acidulated water. It liberates hydrogen gas at cathode and oxygen gas at anode.
Process is applied where the electricity is cheap and it is 99.9% pure
2H2O
2H2 + O2
b) From water gas (Bosch Process)
Water gas is mixed with double the volume of steam and passed through catalyst at 5000
C.
Fe2O3 / Cr2O3
[CO + H2] + H2O
CO2 + H2
5000 C
The water gas is passed through water where carbon dioxide is absorbed. Then hydrogen
gas passed through ammoniac cuprous chloride to remove carbon monoxide. Finally
hydrogen gas is passed through calcium chloride to remove moisture (water vapor).
Properties of hydrogen gas
a) Physical properties
1. It is colorless, odorless and tasteless.
2. It has low density (lightest gas)
3. It is insoluble in water.
4. It get liquefied at -2400C at 20atm.
5. It is good conductor of heat
6. It is readily absorbed by metals
B)Chemical properties
1. It is neutral to litmus paper
2. It is combustible and inflammable gas
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3. Reaction of hydrogen with non – metal
a. With chlorine- hydrogen combines with chlorine slowly in presence of diffused
sunlight to form hydrochloric acid.
H2 + Cl2
2HCl
b. With nitrogen- when the mixture of nitrogen and hydrogen gas in ratio 1:3 is
compressed to 200-500 atm and passed over heated iron catalyst, containing
molybdenum (promoter) at 450-5000C, combine to form ammonia.
N2 + H2
2NH3
c. With sulphur- when dry hydrogen is bubbled through molten sulphur, it reacts
with sulphur to form hydrogen sulphide which smells like rotten egg.
H2 + S
H2 S
4. Reaction with metals. When dry hydrogen gas is passed through heated steam,
highly active metal such as sodium, potassium, calcium, etc they react to form the
corresponding metal hydrides. When the metal hydrides are unstable and decompose
to liberate hydrogen gas on treatment with water.
2Na + H2
2K + H2
2NaH [NaH + H2O
2KI [KH + H2O
NaOH + H2]
KOH + H2]
5. Action with metal oxides (reducing property). When dry hydrogen gas is passed
over strongly heated oxides of copper, iron, lead, etc. hydrogen removes oxygen of
the oxides to form water and free metal.
CuO + H2
Cu + H2O
PbO + H2
Pb + H2O
Fe2O3 + 3H2
2Fe + 3H2O
Uses of hydrogen
1. As a fuel. Because of its high heat of combustion, hydrogen is used as an industrial fuel.
2. Oxy-hydrogen torch. A mixture of hydrogen and oxygen when burnt in a specially
designed apparatus called oxy-hydrogen torch produces temperatures around 25000C
which is used for cutting and welding of metals.
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3. Atomic-hydrogen torch.
4. Synthesis of compounds.
N2 + 3H2
2NH3 ; H2 + Cl2
CO + 2H2
2HCl
CH3OH
5. Hydrogenation of oils.
Oil + H2
Fat (ghee)
6. Synthesis of petrol. (synthetic petrol)
Oxygen
Industrial preparation
a) Fractional distillation of liquid air
The air is passed through fine filters to remove dusts. The air is cooled to about -800 C to
remove water vapor and carbon dioxide as solid. Cold air is compressed to about 100atm
and this warms air. Then air is passed through cool pipes to cool down. The process of
compression followed by expansion is repeated until the air reaches a temperature below
-2000 C and air gets liquefied. Liquid air is fractionally distilled and separated base on
their boiling points. The liquid air is slowly warm up and other gases vaporized and
liquid oxygen remain at the bottom of fractionating column. It change to gas and then
filled in compressed state in steel cylinders.
b) Electrolysis of water.
Water is acidified with sulphuric acid to conduct electricity. It is taken in Hoffman’s
Voltameter. Heavy current is passed through acidulated water. It liberates hydrogen gas
at cathode and oxygen gas at anode. Process is applied where the electricity is cheap and
it is 99.9% pure
2H2O
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2H2 + O2
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Propertied of oxygen gas
a) Physical properties
1. It colorless, odorless & non-poisonous gas
2. It is slightly heavier than gas
3. It is slightly soluble in water
4. It liquefied at normal pressure at -1860C and solidifies at -2180C.
b) Chemical properties
1. It is neutral to litmus gas
2. It is non-combustible substance but help other substance to burn.
3. Oxygen is oxidizing agent and it oxidize all metals (except Ag & Au) and non-metals
(except halogens) to form their oxides.
a) Non – metals
1. With hydrogen – pure hydrogen burns in presence of oxygen to produce the
water
2H2 + O2
2H2O
2. With carbon – red hot charcoal is put in a jar containing oxygen to produce
carbon dioxide
C + O2
CO2
3. With sulphur – when burning sulphur is introduce in the jar containing
oxygen, it burns brightly to produce sulphur dioxide
S +O2
SO2
4. With phosphorus – when a yellow phosphorus is warmed in a deflagrating
spoon and then lowered in a jar containing oxygen, it burns to produce
phosphorus pentaoxide
4P + 5O2
2P2O5
b) Metals
1. With sodium – sodium burns in presence of oxygen to produce sodium oxide
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4Na + O2
2Na2O
2Na + O2
Na2O2
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2. With calcium – when burning Ca is introduced in the jar of oxygen, it burns
to form white ash of calcium oxide.
Ca + O2
2CaO
3. With magnesium – when burning magnesium is introduced in the jar of
oxygen, it burns to form white powder of magnesium oxide.
2Mg + O2
2MgO
4. With iron – when hot iron is introduced in a jar of oxygen, it produces sparks
and form the tri-ferric tetroxide
3Fe + O2
Fe3O4
c) Oxidation of lower oxides to higher oxides
1. Nitric oxides combines with oxygen at room temperature to form nitrogen
dioxide
2NO + O2
2NO2
2. Carbon monoxides burn in oxygen to form carbon dioxide
2CO + O2
2CO2
3. Sulphur dioxide on heating with oxygen at 450 degree centigrade in presence
of catalyst form sulphur trioxide.
2SO2 + O2
2SO3
4. Ammonia gas burns with pale flame in an atmosphere of oxygen to form
nitrogen gas and steam
4NH3 + 3O2
2N2 + 6H2O
5. Iron (II) oxides heating in presence of oxygen form iron (III) oxides
4FeO + O2
2Fe2O3
Uses of oxygen
Oxygen has number of uses in our daily life and industry as described below:
a. Industrial uses
1. In the iron and steel industry.
2. In chemical industries
3. For welding and cutting metals
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4. For blasting of rocks
5. As a rocket fuel.
b. Uses in medicines
1. Artificial respiration
2. Carbogen
3. Anaesthesia.
c. General uses
1. For respiration of all living beings.
2. Helps in quick disposal of dead plants and animals by oxidation.
3. It helps in burning of fuels
4. Oxygen masks.
Nitrogen gas
Industrial preparation
a) Fractional distillation of liquid air
The air is passed through fine filters to remove dusts. The air is cooled to about -800 C to
remove water vapor and carbon dioxide as solid. Cold air is compressed to about 100atm
and this warms air. Then air is passed through cool pipes to cool down. The process of
compression followed by expansion is repeated until the air reaches a temperature below
-2000 C and air gets liquefied. Liquid air is fractionally distilled and separated base on
their boiling points. The liquid air is slowly warm up and other gases vaporized. At -1950
C nitrogen vaporizes and nitrogen gas is collected.
Properties of nitrogen gas
Physical properties
1. It is colorless, odorless & tasteless gas
2. It is slightly lighter than air
3. It s slightly soluble in water
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4. It can be liquefied at -1950 C and solidifies at – 210.50C
5. It is non-poisonous gas
Chemical properties
1. It s chemically inert gas at room temperature
2. It is neutral to litmus
3. It is neither combustible nor supporter of combustion
4. Reaction with non-metals
a) Hydrogen – when nitrogen and hydrogen are put in the ratio of 1:3 and compressed to
200-900atm passed over heated iron (catalyst) containing promoter (molybdenum),
they combine to form ammonia
N2 + 3H2
2NH3
b) Oxygen – nitrogen combines with oxygen during thunder and lightning or under
electric arc at a temperature of 30000C t form NO
N2 + O2
2NO
5. Reaction with metals: nitrogen combines with highly electropositive metals like lithium,
calcium, magnesium, aluminum, etc on strong heating to form their respective nitrides.
And nitrides on treatment with boiling water form ammonia and respective hydroxides
6Li + N2
2Li3N
3Ca + N2
Ca3N2
Ca3N2 + 6H2O
3Ca(OH)2 + 2NH3
2Al + N2
2AlN
AlN + 3H2O
Al(OH)3 + NH3
3Mg + N2
Mg3N2
Mg3N2 + 6H2O
3Mg(OH)3 + 2NH3
6. Reaction with chemical compounds : on strong heating, nitrogen combines with
compound like Al2O3 and CaC2
Al2O3 + N + 3C
CaC2 + N
2AlN + 3CO
CaNCN + C
Uses of nitrogen
The major uses of nitrogen are based on the three characteristics of nitrogen as follows:
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a. Uses based on inert nature
1. Dilutes the effect of oxygen in the air.
2. Used in high temperature thermometers
3. Canned food stuffs
4. Electric bulbs
5. In industries
6. In welding
b. Uses based on low boiling point
1. As refrigerant for freezing food stuff
2. Liquid nitrogen is used to store living cells and biologically important tissues.
c. Uses based on nitrogen being a constituent of proteins
1. Used by the plants for the protein synthesis.
2. Used for the manufacture of fertilizers.
Nitrogen dioxide
Preparation
Nitrogen dioxide is produced by following method:
a) Oxidation of nitric oxide by air (oxygen)
2 NO + O2
2 NO2
b) The thermal decomposition of some metal nitrates also liberate nitrogen oxide
2 Pb(NO3)2
2 PbO + 4 NO2 + O2
Properties of nitrogen dioxide
Physical properties
 It is a reddish brown gas.
 It has pungent smell.
 It is heavier than air (denser than air)
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 The substance is corrosive to the skin and the respiratory tract.
 Boiling point 21.2°C and melting point is -11.2°C
Chemical properties
1. Reaction with water
It reacts with water to form a mixture of two acids.
2NO2 (g) + H2O (l)
HNO2(aq) + HNO3(aq)
2. Reaction with alkalis
It reacts with alkalis to form salts and water.
2KOH (aq) + 2NO2 (g)
KNO3(aq) + KNO2(aq) + H2O(l)
3. Action of heat.
On heating it gives nitrogen oxides and oxygen.
2NO2 (g)
2NO (g) + O2 (g)
4. Reduction by reducing agent
Nitrogen dioxide can also be reduced to lower oxide or nitrogen by reducing agents.
Heated copper reduce nitrogen dioxide to nitrogen gas and copper will form copper(II)
oxide (CuO) and nitrogen gas.
4Cu(s) + 2NO2 (g)
4CuO(s) + N2 (g)
5. Support of combustion
Nitrogen dioxide will support the combustion of burning substances when heated enough
to release its oxygen for combustion. Oxygen produces as a byproduct help in
combustion.
2NO2 (g)
N2(g) + 2O2(g)
Uses
 Nitrogen Dioxide is used as rocket fuel, a flour bleaching agent
 Used in increasing the wet strength of paper
 Nitrogen is used for the production of ammonia, nitric acid and fertilizers.
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Nitrous oxide (laughing gas)
Industrial preparation
Nitrous oxide is most commonly prepared by careful heating of ammonium nitrate, which
decomposes into nitrous oxide and water vapor.
NH4NO3 (s) → 2 H2O (g) + N2O (g)
Properties of nitrous oxide
Physical properties
 It is 1 1/2 times denser than air,
 It is colorless, tasteless, and has a slightly sweet odor
 It’s boiling point (°F) is -128.3and melting point (°F) is -131
Chemical properties
 it decomposes to produce nitrogen and oxygen gas.
2N2O(g) → 2N2(g) + O2(g)
 Reaction with sulphur
S(s) + 2N2O(g) → SO2(g) + 2N2(g)
 Reaction with magnesium
Mg(s) + N2O(g) → MgO(s) + N2(g)
 Reaction with copper
Cu(s) + N2O(g) → N2(g) + CuO(s)
Uses
 Nitrous oxide can be used as an oxidizer in a rocket motor
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 In vehicle racing, nitrous allows the engine to burn more fuel by providing more oxygen
than air alone, resulting in a more powerful combustion
 The gas is approved for use as a food additive
 nitrous oxide has been used for anesthesia in dentistry
 use in the recreation
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CARBON DIOXIDE
Industrial Preparation
u
CALCIUM
CARBON
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+ HYDROCHLORIC
=
CALCIUM +
WATER
+
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CARBONATE
30th April 2012
ACID
CHLORIDE
DIOXIDE
(MARBLE)
CaCO3
+
2HCl
=
CaCl2 + H2O
+ CO2
Physical Properties of CO2

CO2 gas has a slightly irritating odor, is colorless and heavier than air.

It cannot sustain life.

It freezes at -78.5 °C to form carbon dioxide snow.

Liquid density : 1032 kg/m3 · Liquid/gas equivalent: 845 vol/vol

Colorless

Inert, non flammable
Chemical Properties of CO2

In an aqueous solution it forms carbonic acid.

Latent heat of vaporization : 571.08 kJ/kg

Vapor pressure : 58.5 bar

It will not burn or support combustion.
Applications/Uses
Precursor to chemicals
In the chemical industry, carbon dioxide is mainly consumed as an ingredient in the production of urea
and methanol.
Foods
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Carbon dioxide is a food additive used as a propellant and acidity regulator in the food industry.
Beverages
Carbon dioxide is used to produce carbonated soft drinks and soda water.
Wine making
Carbon dioxide in the form of dry ice is often used in the wine making process to cool down bunches of
grapes quickly after picking to help prevent spontaneous fermentation by wild yeasts.
Fire extinguisher
Carbon dioxide extinguishes flames, and some fire extinguishers, especially those designed for electrical
fires; contain liquid carbon dioxide under pressure.
Agricultural and biological applications
Plants require carbon dioxide to conduct photosynthesis. Greenhouses may enrich their atmospheres with
additional CO2 to sustain and increase plant growth. A
Refrigerant
Liquid and solid carbon dioxide are important refrigerants, especially in the food industry, where they
are employed during the transportation and storage of ice cream and other frozen foods. Solid carbon
dioxide is called "dry ice" and is used for small shipments where refrigeration equipment is not practical.
Carbon dioxide can be used as a mean of controlling the pH of swimming pools, by continuously adding
gas to the water, thus keeping the pH level from rising.
Carbon monoxide
Industrial production
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A major industrial source of CO is producer gas, a mixture containing mostly carbon monoxide
and nitrogen, formed by combustion of carbon in air at high temperature when there is an excess
of carbon. In an oven, air is passed through a bed of coke. The initially produced CO2
equilibrates with the remaining hot carbon to give CO. The reaction of O2 with carbon to give
CO is described as the Boudouard equilibrium. Above 800 °C, CO is the predominant product:
O2 + 2 C → 2 CO (ΔH = −221 kJ/mol)
Another source is "water gas", a mixture of hydrogen and carbon monoxide produced through
endothermic reaction of steam and carbon:
H2O + C → H2 + CO (ΔH = +131 kJ/mol)
Other similar "synthesis gases" can be obtained from natural gas and other fuels.
Carbon monoxide is also a byproduct of the reduction of metal oxide ores with carbon as shown
below.
MO + C → M + CO
Since CO is a gas, the reduction process can be driven by heating, exploiting the positive entropy
of reaction.
Physical properties

is a colourless, odourless, neutral, gaseous oxide, which is highly poisonous,

Is sparingly soluble in water, but is soluble in ethanol and in benzene.

It has
o
Melting Point : -199 degC
o
Boiling Point : -91.5 degC
o
Relative density : 1.25
Chemical properties
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
is a flammable and highly toxic gas,

is a neutral oxide which burns in air to give carbon dioxide,

is a good reducing agent, and is used for that purpose in industry,

CuO + CO ==>

And, is an important industrial gas, which is widely used as a fuel.

It is also an important reducing agent in the chemical industry.
Cu + CO2
Applications/Uses
Chemical industry
Carbon monoxide is an industrial gas.
Large quantities of aldehydes are produced by the hydroformylation reaction of alkenes, carbon
monoxide, and H2..
It is also used for the industrial production of acetic acid.
Industrial preparation of methane gas
Methane gas is prepared on large scale from natural gas by liquefaction. We also prepared by
following processes
(a) From carbon monoxide: A mixture of carbon monoxide and hydrogen is passed over a
catalyst containing nickel and carbon at when methane is formed.
Bi + C
CO + 3 H2 ————→ CH4 + H2O
250o C
(c) Synthesis: By striking an electric arc between carbon electrodes in an atmosphere of
hydrogen at 1200oC, methane is formed.
1200o C
C + 2 H2 ————→ CH4
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By passing a mixture of hydrogen sulphide and carbon disulphide vapor through red hot copper,
methane is formed.
High temperature
CS2 + 2H2S + 8Cu ————→ CH4 + 4Cu2S
Properties of methane (marsh gas)
Physical properties
1. Methane gas is colorless, odorless & tasteless gas
2. Methane gas has density lighter than air.
3. Methane becomes liquid below 112 K and solidifies at 90.5 K.
4. This gas is slightly soluble in water but soluble in organic solvents.
Chemical properties
1. It reacts with oxygen to give huge amount of energy
CH4 + 2O2
CO2 + 2H2O
2. It reacts with chlorine gas
CH4 + 5Cl2
CH3Cl+ CH2Cl2+ CHCl3+ CCl4
3. It decomposes to acetylene at high temperature
4. 2CH4
C2H2+3H2
Uses of methane gas
 Methane is useful in the testing of gas appliances which are to be used for natural gas
areas.
 It is one of the raw materials used in the production of ethanol, methyl chloride, ethylene
chloride, and is also used to produce ammonia and acetylene.
 High purity methane is burned to form a high quality carbon black which is used in a
variety of electronic components.
 Gas is widely used as a fuel in homes, commercial establishments, and factories
Industrial preparation of acetylene
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The industrial preparation of acetylene was discover by the Friedrich Wohler in 1862. Acetylene
is produce by hydrolysis of water on calcium carbide.
CaC2 + 2H2O
Ca(OH)2 + C2H2
Properties of acetylene
Physical properties
 It is a colorless and flammable gas.
 It has a ginger like odor (100% pure is odorless)
 Boiling point is -120.60 F
 Melting point is -113.00 F
Chemical properties
 Acetylene can be decomposed to its elements with the liberation of heat
 Together with air it forms an explosive mixture
 Thermal decomposition produces carbon monoxide that is poisonous
 It possesses a reactive triple bond between carbon and carbon.
 it reacts with strong bases to form acetylide salts
Uses of acetylene
 In chemical synthesis
 As Oxyacetylene gas welding and cutting due to the high temperature of the flame.
Propane preparation
Propane is produced as a by-product of two other processes, natural gas processing and petroleum
refining. The processing of natural gas involves removal of butane, propane, and large amounts of ethane
from the raw gas, in order to prevent condensation of these volatiles in natural gas pipelines. Additionally,
oil refineries produce some propane as a by-product of cracking petroleum into gasoline or heating oil.
Properties of propane
Physical properties
 Propane is heavier than air (1.5 times as dense).
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 Propane is a liquid at -50°F and boils at -44°F
 In its raw state, propane sinks and pools at the floor
 Liquid propane will flash to a vapor at atmospheric pressure and appears white due to
moisture condensing from the air
 Propane is non-toxic however it causes mild asphyxiation lack of oxygen
Chemical properties
 In the presence of excess oxygen, propane burns to form water and carbon dioxide.
C3H8 + 5 O2
3 CO2 + 4 H2O + heat
 Incomplete burning of the propane yields water, carbon monoxide, carbon dioxide and
carbon
2 C3H8 + 7 O2
2 CO2 + 2 CO + 2 C + 8 H2O + heat
Uses
 Propane is also being used increasingly for vehicle fuels
 As a gas absorption refrigerator
 As domestic and industrial fuel
 Propane is the primary fuel for hot air balloons.
 It is used in semiconductor manufacture to deposit silicon carbide
Preparation of ammonia
a) Haber process
It is prepared at 300-3500C and 150-250bar. The gas is passed over beds of catalyst with
cooling between each pass to maintain a reasonable equilibrium constant. On each pass of
gases, 15% of gases are converted to ammonia and unused gas is recycled.
N2 (g) + 3 H2 (g)
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2 NH3 (g)
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Properties of ammonia
Physical properties
 Ammonia is extremely soluble in water and is frequently used as a water solution called
aqua ammonia.
 anhydrous ammonia is a clear, colorless liquid or gas, free from visible impurities
 It is 99.95 percent pure ammonia.
 Anhydrous ammonia is nonflammable.
Chemical properties
 Ammonia, especially in the presence of moisture, reacts with and corrodes copper, zinc,
and many alloys.
 Ammonia will combine with mercury to form a fulminate which is an unstable explosive
compound.
Uses of Ammonia
 Most of the ammonia used in the world is used in fertilizer either in salt or liquid form.
 Almost all synthetically derived nitrogen is made from ammonia. Nitric acid is used in
fertilizers and explosives.
 Household ammonia is used as a surface cleaner in a diluted form.
 Ammonia is used in industrial refrigeration applications and hockey rinks as it has
favorable vaporization properties
 It is used in geothermal power plants in an ammonia-water mixture that is boiled.
 Ammonia is used to scrub Sulfur dioxide from the burning fossil fuels used in power
plants. It is also used to neutralize the nitrogen oxide produced by diesel engines.
 It is used in animal feed as an antimicrobial. It is also used to disinfect beef products
before sale.
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 Liquid ammonia is used in textiles to treat cotton materials and in the pre-washing of
wool
Preparation of ethane
Ethane is mostly separated from methane by liquefying it at cryogenic temperatures. In this
process, chilled gas expands through a turbine. As the gas expands, its temperature drops to
about 100°C. At this low temperature, gaseous methane can be separated from the liquefied
ethane and heavier hydrocarbons by distillation. Further distillation then separates ethane from
the propane and heavier hydrocarbons.
Properties of ethane
Physical properties
 Odorless and colorless gas at STP
 The melting point of ethane is -181.76° C and boiling point is -88.6° C
 It is soluble in polar solvents like water.
Chemical properties
 Incomplete or partial combustion of the gas leads to the production of single-carbon
compounds like carbon monoxide and formaldehyde.
 Additional trivial products produced during ethane's partial combustion are
acetaldehyde, methanol, ethanol, and methane
Uses
 Ethane is primarily used for the production of ethylene through the process of steamcracking
 Use as a fuel
 Ethane can be used as a refrigerant in cryogenic refrigeration systems.
Preparation of Ethylene
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Ethylene is produced in the petrochemical industry by steam cracking. In this process, gaseous or
light liquid hydrocarbons are heated to 750-950 °C, inducing numerous free radical reactions
followed by immediate quench to stop these reactions. This process converts large hydrocarbons
into smaller ones and make it unsaturated hydrocarbon. Ethylene is separated from complex
mixture by repeated compression and distillation. Heavier feed stocks require two quench towers
downstream of the cracking furnaces to process water.
Physical properties
 colorless gas at room temperature and pressure
 Melting point -169oC and Boiling point -104oC
 slightly sweet smell
 flammable
 non-polar molecule
 soluble in non-polar solvents & insoluble in polar solvents like water
Chemical properties
 Action of bromine
CH2=CH2 + Br2
CH2BrCH2Br (1,2-dibromoethane)
 Addition of Chlorine
CH2=CH2 + Cl2 AlCl3
CH2ClCH2Cl (1,2-dichloroethane)
 Addition of Hydrogen bromide
CH2=CH2 + HBr
CH3CH2Br (bromoethane)
 Addition of Hydrogen chloride
CH2=CH2 + HCl
 Addition of Hydrogen
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CH3CH2Cl (chloroethane)
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CH2=CH2 + H2
30th April 2012
CH3CH3 (ethane)
 Addition of Water
CH2=CH2 + H2O H3PO4
CH3CH2OH (ethanol)
 Combustion
CH2=CH2 + 3O2
2CO2 + 2H2O
Uses
 Production of Polythene
 Production of Industrial Alcohol
 Ethylene is also used as a plant hormone to control the ripening and colour development
of fruit
References
About ethylene gas. (n.d). Retrieved on March 15th from http://www.ethylenegas.com/
Ethylene. htm
Acetylene. (n.d). Retrieved on April 25th from http://en.wikipedia.org/wiki/Acetylene
Ethane gas. (n.d). Retrieved on March 15th from http://www.wisegeek.com/what-is-ethane
.htm
Ethene (ethylene): Properties, Production & Use. (n.d). Retrieved on March 25th from
http ://www.ausetute.com.au/ethene.html
Properties of acetylene. (n.d). Retrieved on March 18th fromhttp://encyclopedia.airliquide.
com/ Encyclopedia.asp?GasID=1
Properties of acetylene. (n.d). Retrieved on March 20th from http://encyclopedia.airliquide
.com/Encyclopedia.asp?GasID=29
Properties of ammonia. (n.d). Retrieved on March 26th from http://www.osha.gov/
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SLTC /etools/ammonia_refrigeration/ammonia/index.html
Properties of propane. (n.d). Retrieved on March 30th from http://www.propane101.
com/aboutpropane.htm
Uses of ammonia. (n.d). Retrieved on April 15th from http://wanttoknowit.com/
uses-of-ammonia/
Helium
Industrial Preparation
Helium is separated by liquefying the other gases present in the natural gas; it is then either
further purified or stored for later purification and use. Some helium is extracted directly from
the atmosphere. It is the end product of energy-releasing fusion processes in stars.
Properties (Physical and Chemical properties)
The nucleus of the helium-4 atom is identical with an alpha particle.
Helium is the least reactive noble gas after neon and thus the second least reactive of all
elements. Because of helium's relatively low molar (atomic) mass, its thermal conductivity,
specific heat, and sound speed in the gas phase are all greater than any other gas except
hydrogen.
Uses/applications
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 A mixture of helium and oxygen is often supplied as a breathing mixture for deep-sea
divers and caisson workers.
 Helium can also be used in electric arc welding, in growing crystals of silicon and
germanium for semiconductors, and in refining titanium and zirconium metals..
Neon
Industrial Preparation
Fractional distillation from liquid air. Air is liquified, and as the temperature is raised slowly,
different gases come out of the mix based on their boiling point.
Properties (Physical and Chemical properties)
A colorless, odorless, nonflammable, inert Gas.
Applications/applications
 Used as a filling gas in spark chamber particle detectors, Geiger tubes and other
detectors, fluorescent lamps, sodium discharge lamps, digital display tubes, stroboscope
lights, in signs in mixtures with argon, filament lamps, and telephone line surge arrestors.
 Used as a buffer gas or the active medium in various types of gas lasers such as
helium/neon, excimer or copper vapor lasers.
 Used as a carrier gas in chromatography applications.
 Liquid neon is used in the following: liquid hydrogen replacement studies, cryo-sorption
and cryo-pumping, nuclear particle detection in bubble chambers, and in lung diffusion
gas
Argon
Industrial Preparation
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Argon is produced industrially by the fractional distillation of liquid air in a cryogenic air
separation unit; a process that separates liquid nitrogen, which boils at 77.3 K, from argon, which
boils at 87.3 K and liquid oxygen, which boils at 90.2 K.
Properties (Physical and Chemical properties)
Argon is colorless, odorless, and nontoxic as a solid, liquid, and gas.
Argon is chemically inert under most conditions and forms no confirmed stable compounds at
normal temperature.
Applications/Uses
 Argon is mostly used as an inert shielding gas in welding and other high-temperature
industrial processes where ordinarily non-reactive substances become reactive.
 Argon gas also has uses in incandescent and fluorescent lighting, and other types of gas
discharge tubes.
 Argon is sometimes used for extinguishing fires where damage to equipment is to be
avoided.
Medical use
 Cryosurgery procedures such as cryoablation use liquefied argon to destroy cancer cells.
 Incandescent lights are filled with argon, to preserve the filaments at high temperature
from oxidation. It is used for the specific way it ionizes and emits light. Gas-discharge
lamps filled with argon provide blue light. Argon is also used for the creation of blue and
green laser light.
Krypton
Industrial Preparation
Making liquid air
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1 .Air is first passed through filters to remove particulate matter such as dust. The clean air is
then exposed to an alkali which removes water and carbon dioxide.
2. The clean, dry air is compressed under high pressure. Iit is then cooled by refrigeration.
3. The cooled, compressed air passes through coils winding through an empty chamber. A
portion of the air, which is compressed to a pressure about two hundred times greater than
normal, is allowed to expand into the chamber. This sudden expansion absorbs heat from the
coils, cooling the compressed air.
Separating the gases
4. Gases with very low boiling points are not transformed into liquids and can be removed
from the others directly.
5. A process known as fractional distillation separates the various elements found in liquid
air.
6. The liquid air is allowed to warm slowly. As the temperature increases the substances
with the lowest boiling points become gases and can be removed from the remaining
liquid. Krypton and xenon have higher boiling points and remain in the liquid state.
7. The liquid krypton and xenon are absorbed onto silica gel or onto activated charcoal.
They are then once again subjected to fractional distillation. The liquid mixture is
warmed slowly until the krypton is transformed into a gas. The xenon has a somewhat
higher boiling point and remains behind as a liquid.
8. The krypton is purified by passing it over hot titanium metal.
Properties (Physical and Chemical properties)
Under normal conditions, krypton is a colorless, tasteless, odorless gas.
Its density at normal temperature and pressure is about 0.5 oz per gallon.
At extremely low temperatures, krypton may exist as a liquid or a solid.
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Its B.P -243.81° F and F.B is -251.27° F
Applications/Uses
 Krypton is used with argon in fluorescent lights to improve their brightness
 And with nitrogen in incandescent lights to extend their lifetime.
 It is also used in flashbulbs to produce a very bright light and
 For use in high-speed photography.
Xenon
Industrial Preparation
Xenon is obtained commercially as a byproduct of the separation of air into oxygen and nitrogen.
After this separation fractional distillation is applied in a double-column plant, the liquid oxygen
produced will contain small quantities of krypton and xenon. By additional fractional distillation
steps, the liquid oxygen may be enriched to contain 0.1–0.2% of a krypton/xenon mixture, which
is extracted either via adsorption onto silica gel or by distillation. Finally, the krypton/xenon
mixture may be separated into krypton and xenon via distillation
Properties (Physical and Chemical properties)
Colorless gas, exhibiting a blue glow when placed in a high voltage electric field.
At standard temperature and pressure, pure xenon gas has a density of 5.761 kg/m3
Applications/Uses
 Xenon is used in light-emitting devices called xenon flash lamps, which are used in
photographic flashes and stroboscopic lamps.
 Xenon has been used as a general anesthetic.
 Xenon is finding application in treating brain injuries.
 Gamma emission from the radioisotope
lungs, and brain.
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133
Xe of xenon can be used to image the heart,
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Radon
Industrial Preparation
Radon is obtained as a by-product of uraniferous ores processing after transferring into 1%
solutions of hydrochloric or hydrobromic acids.
Radon is produced by a solution of radium-226 . Radium-226 decays by alpha-particle emission
also produces radon which collects over samples of radium-226 at a rate of about 1 mm3/day per
gram of radium.
Properties (Physical and Chemical properties)
Physical properties
Radon is a colorless and odorless gas, and therefore not detectable by human senses alone. At
standard temperature and pressure its density of 9.73 kg/m3. Radon is one of the densest gases at
room temperature and is the densest of the noble gases. its freezing point of 202 K.
Chemical properties
Radon is sparingly soluble in water, but more soluble than lighter noble gases. Radon is
appreciably more soluble in organic liquids than in water.
Radon can be oxidized by a few powerful oxidizing agents such as fluorine, thus forming radon
fluoride. It decomposes back to elements at a temperature of above 250 °C. It has a low
volatility
Applications/Uses
 It is applied in the treatment of maladies.
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 Radon's molecule-damaging radioactivity has been used to kill cancerous cells.
 Health mines and spas
 Radon is used to study atmospheric transport and to explore petroleum and uranium.
A. CHLORINE
Preparation
On a commercial scale chlorine is prepared by electrolysis of an aqueous solution of sodium
chloride (brine solution) when Cl2 is evolved at the anode and H2 is evolved at the cathode.
Electrolysis
2NaCl + 2H2O ———————> 2NaOH + Cl2 + H2
It can also be prepared by electrolysis of molten NaCl (Down’s cell for the manufacture of
metallic sodium). When Cl2 is evolved at the anode and sodium metal at the cathode.
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Electrolysis
2NaCl + 2H2O ———————> 2Na + Cl2
Properties: It combines with metals and non metals to form chlorides. It decomposes water
forming HCl and HClO which is unstable and decomposes giving nascent oxygen which is
responsible for oxidizing and bleaching action of chlorine.
Cl2 + H2O ——> HCl + HClO; HClO —> HCl + [O]
Colored matter + O —> Colorless matter.
The bleaching action is permanent and color is not restored on standing. However, it cannot
be used for bleaching delicate articles such as straw, silk, wool etc. which are damaged by it.
Cl2 oxidizes Br– and I– ions to Br2 and I2 respectively.
Cl2 + 2X– ——> 2Cl– + X2 (X = Br or I).
It combines with alkalies forming hypochlorite and chlorate salts in cold and hot conditions
respectively.
Cold
2NaOH (dil.) + Cl2 ————> NaCl + NaClO + H2O
Heat
2NaOH (conc.) + 3Cl2 ————> 5NaCl + NaClO3 + 3H2O
During these reactions, halogen is simultaneously reduced to X– ion and is oxidized to
either hypohalite (XO–) or halate (XO–3) ion. Such reactions are called disproportionation
reactions.
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With slaked lime, Cl2 gives bleaching powder (CaOCl2)
Ca (OH)2 + Cl2 ———> CaOCl2 + H2O
With ammonia, Cl2 reacts as follows:
8NH3 (excess) + 3Cl2 ———> 6 NH4Cl + N2
NH3 + 3Cl2(excess) ———> NCl3 + 3HCl
With SO2 and CO, addition compounds are formed
SO2 (dry) + Cl2 ——> SO2Cl2 (Sulfuryl chloride)
CO + Cl2 ——> COCl2 (Carbonyl chloride or phosgene)
Uses of Chlorine
1. Chlorine is largely used for the sterilization of municipal supply water.
2. It is used as a bleaching agent in paper industry and textile industry
3. It is used in the manufacture of several dyestuff and explosive
4. It is used in the manufacture of synthetic plastics such PVC
5. It is used in the manufacture of refrigerants such as Freon (CCl2F2)
B. FLUORINE
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Preparation: F2 is now prepared by electrolysis of a solution of KHF2 (1 part) in anyhydrous
HF (5 parts) in a vessel (modern method) made of Ni — Cu alloy or Ni — Cu — Fe alloy called
the Monel metal using carbon electrodes. During the electrolysis following reactions occur.
KHF2 ————> KF + HF; KF ———> K+ + F–;
At cathode: K+ + e– ———> K; 2K + 2HF ———> 2 KF + H2
At anode:
F– ————> F + e– ; F + F ———> F2
Properties: It is the most reactive of all the halogens. It combines with metals as well as nonmetals to form fluorides. It decomposes water forming O2 and O3 and reacts vigorously with
hydrogen of hydrocarbons leaving behind fluorinated hydrocarbons.
Cold
2H2O + 2F2 ————> 4HF + O2
Oxidation
Hot
3H2O + 3F2 ————> 6HF + O3
Oxidation
(HF being a volatile liquid fumes in air)
F2
F2
F2
F2
CH4 ———> CH3F ———> CH2F2 ———> CHF3 ———> CF4
It is a strong oxidizing agent and oxidizes KClO3 to KClO4, KIO3 to KIO4 and bisulfates to
peroxy sulfates.
KCIO3 + F2 + H2O ———> KCIO4 + H2F2
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2NaHSO4 + F2 ———> Na2S2O6 + 2HF
It reacts with to form nitrogen and with H2S forming SF6.
2NH3 + 3F2 ——> N2 + 6 HF (oxidation reaction)
H2S + 4F2 ——> SF6 + 2 HF
Fluorine reacts with cold and dilute sodium hydroxide solution to give oxygen difluoride (OF2)
2F2 + 2NaOH (cold, dil) ——> 2NaF + H2O + OF2
However, with hot and concentrated sodium hydroxide solution it gives oxygen
2F2 + 4NaOH (hot, conc.) ——> 4NaF + 2H2O + O2
Since F2 is the strongest oxidizing agent, it is always reduced and hence does not show
disproportionation reactions while others halogens do.
F2 oxidizes all other halide ions to the corresponding halogens (F2 + 2 X– ———> 2F– + X2); (X
= Cl, Br or I)
Uses of fluorine
1. Fluorine is largely used in the manufacture of UF6 for nuclear generation and SF6 for high
voltage insulation.
2. It is used in the preparation of DDFT which is more efficient fungicide than DDT
3. It is used to obtain the polymer such as Teflon. The
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SULPHUR DIOXIDE
Chemical properties (Reactions)
As a reducing agent:
Sulphur dioxide acts as a reducing agent by supplying electrons or gaining oxygen from other
substances. Examples include:
The bleaching action: This is due to sulphurous acid which removes oxygen from the dye.
Equations of reaction
With acidified dichromate (VI) solution
Equation of reaction:
Observation:
Solution turns from orange to green.
With potassium manganate(VII) solution
Equation of reaction
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Observation:
Solution turns from purple/pink to colourless
With iron (III) sulphate solution
Iron (III) ions in solution are reduced by sulphur dioxide to iron (II) ions.
Equation of reaction
Observation:
Solution turns from brown to green
With bromine solution
Bromine in reduced to bromide ions.
Equation of reaction
With iodine solution
Iodine is reduced to iodide ions.
Equation of reaction
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With sodium hydroxide solution
With a little sulphur dioxide bubbled through an excess of the alkali, a normal salt is formed but
equimular quantities react to form an acid salt.
Equation of reaction
(ii) Examples in which sulphur dioxide acts as an oxidising agent include:
With burning magnesium ribbon
Equation of reaction
Mixture of white and yellow solids deposited at the bottom and sides of the jar.
Equation of reaction
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References
Srivastava,H.C.(2011). Nootan ISC Chemistry. pp. 570-611. Uttar Pradesh : Nageen Prakashan
private limited.
Madan,R.D. & Bisht,B.S.(2007). ISC Chemistry for Class XI. Pp.484-561. New Delhi: S Chand
and company pvt limted.
http://www.transtutors.com/chemistry-homework-help/S-and-P-block-elements/occurrencepreparation-of-fluorine.aspx
References
Radon (n.d). Retrieved on 15th April 2012 from http://en.wikipedia.org/wiki/Radon
Natural occurrence and Preparation (n.d) Retrieved on 15th April 20120 from
http://www.infoplease.com/ce6/sci/A0858584.html#ixzz1sl2iqBCM
Retrieved on http://www.infoplease.com/ce6/sci/A0858585.html#ixzz1sl6MaPnH
Retrieved on 23rd March 2012 from
http://answers.yahoo.com/question/index?qid=20071201122849AAKVH31
Krypton (n.d) retrieved on 28th April 2012 from http://www.enotes.com/kryptonreference/krypton-192060
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Retrieved on 30th March 2012 from http://www.uigi.com/argon.html
Industrial preparation of Carbon dioxide (n.d). Retrieved on 17th April 2012 from
http://www.lcc.ukf.net/KS3Chem/gasco2.htm
Industrial
production
(n.d).
Retrieved
on
http://www.ucc.ie/academic/chem/dolchem/html/comp/co.html
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April
2012
from
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