SLM- preparation of gases

1. Self Learning Material
Submitted by –
Meenu kumari
14162051
B.Ed Program 2014-15

2. PREPARATION OF GASES
There are many gases in air, such as Oxygen, Carbon dioxide, Hydrogen,
Nitrogen etc. All these are very important for living beings.The atmosphere
of earth is a layer of gases surrounding the planet Earth that is retained by
Earth’s gravity. Air is mainly composed of nitrogen, oxygen and argon.
OXYGEN
Oxygen occurs in the free state as a gas, to the extent of 21 percent by
volume or 23 percent by weight in the atmosphere.
Combined oxygen also occurs
1. in water
2. in vegetable and animal tissues,
3. in nearly all rocks and
4. in many minerals
Oxygen occurs to a larger extent in the earth’s crust than any other
element.
PREPARATION
The most convenient method for preparing oxygen in the laboratory
involves either the catalytic decomposition of solid potassium chlorate or
the catalytic decomposition of hydrogen peroxide.
1. Preparation of oxygen using potassium chlorate
Potassium chlorate decomposes at a low temperature if previously mixed
with magnesium dioxide which is a catalyst for the decomposition. Only the
potassium chlorate is decomposed and no perchlorate formed.

3. 2KClO3 ===> 2 KCl + 3 O2
2. Preparation of oxygen using Potassium permanganate (KMnO4)
Potassium permanganate which is a purple crystalline solid, decomposed
without fusing on heating to 240 degC, producing crackling sound forming a
black powder consisting of a mixture of potassium mangnate and
manganese dioxide and releasing oxygen.
KMnO4 ===> K2MnO4 + MnO2 + O2
Potassium potassium Manganese Oxygen
Permanganate mangnate dioxide
Physical Properties
Oxygen is colorless,odourless and tasteless. It is sparingly soluble in water
and helps in combustion.

4. Chemical Properties
1. Oxygen reacts with metal and forms out metal oxides
2Mg + O2 ---------------> 2MgO
Magnesium Oxygen Magnesium oxide
2. Oxides of metal react with water and form hydroxides of metal.
MgO + 2H2O -----------------> Mg(OH)2
Magnesium oxide Water Magnesium hydroxide
3. Oxygen reacts with non-metals and gives of non metals.
S + O2 ----------------------> SO2
Sulphur Oxygen Sulphur dioxide gas
4.Oxides of non-metals react with water and give salts.
SO2 + H2O -------------------> H2SO3
Sulphur dioxide water Sulphurous acid
Uses of Oxygen
1. Every living being makes use of Oxygen in respiration. It dissolves in
water hence creatures living under water also make use of dissolved
Oxygen for respiration.
2. Hand pumps of specialtypes are made for the patients suffering from the
diseases like Pneumonia and Lung diseases. In this hand pump, there is
an upper valve, when it is pressed a reaction takes place between Sodium

5. peroxide (Na2O2) and water forming oxygen. Using the released Oxygen,
the patient gets instant relief.
3. Oxygen is used to produce flames (31000 –
33000
C). With the help of
these flames, metals can be cut or metals can be joined together.
4. Oxygen is very necessary in the production of chlorine, Nitric acid,
Sulphuric acid etc.
CARBON DIOXIDE
Carbon dioxide is anaturally occurring chemical compound composed of
two oxygen atoms each covalently doubled bonded to a single carbon
atom.Carbon dioxide dissolves in the ocean to form carbonic, bicarbonate
and carbonate.
The oceans act as an enormous carbon sink, and taken up about a third of
CO2 emitted by human activity.
Preparation
Add three spatulas full of calcium carbonate chips to the flask. Pouring
dilute hydrochloric acid into the top of the funnel; ensure that the liquid
covers the tip of the funnel in the flask. Uncover gas jar and place a lit
candle over the mouth of the jar.
CaCO3(s) + 2HCl(aq) ----------> CaCl2(aq) + H2O(I) + CO2(g)
Calcium carbonate Hydrochloric acid Calcium chloride water Carbondioxide

6. Physical Properties:
It is colorless, odourless and tasteless. Sparingly in water and heavier than
other gases.
Chemical Properties:
1. Take water in the bowl. Dissolve slaked lime in this water and allow it to
settle down. Remove the top layer of water from the bowl/dish and let the
precipitation of lime remain in the bowl/dish
By the reaction of Calcium hydroxide with Carbon dioxide, calcium and
water are obtained.
Ca(OH)2 + CO2 ------------------> CaCO3 + H2O
Slaked lime Carbodioxide Calcium carbonate water
2. On reacting Carbon dioxide with Calcium Carbonate and water, it
produces calcium bicarbonate.

7. CaCO3 + H2O + CO2 ----------------> Ca(HCO)3
Calcium carbonate water carbondioxide Calciumbicarbonate
3. On heating Carbondioxide with water at high pressure, Carbonic acid is
CO2(Calciumdioxide) + H2O (water)---------------> H2CO3(carbonic acid)
4. With the process of reaction of Carbon dioxide with metal oxides, metals
carbonates are obtained.
MgO + CO2 -------------> MgCO3
Magnesium oxide carbondioxide Magnesium carbonate
5. With the process of reaction of Carbon dioxide with sodium hydroxide,
water soluble sodium carbonate (washing soda) and sodium bicarbonate.
2NaOH + CO2 --------------> Na2CO3 + H2O
Sodium hydroxide carbon dioxide Sodium carbonate water
2Na2CO3 + H2O + CO2--------------> 2NaHCO3
Sodium Carbonate water carbon dioxide Sodium Bicarbonate
Uses of Caron dioxide:
It is used in photosynthesis by vegetation, extinguishing fire, bringing
fermentation for idli, dhosa etc, preparation of cold drinks, washing soda,
baking soda.
Solid Carbon dioxide is known as ‘Dry Ice’. It is used for cooling agent.
HYDROGEN:
Hydrogen is a chemical element with chemical symbol H and atomic
number 1. It is lightest element and the most abundant element in universe.

8. Preparation:
1. Hydrogen can be made by reaction of any active metal like magnesium
or zinc with a strong acid such as H2SO4 OR HCl. In a test tube,add
magnesium strip or pieces of iron nails in it. Adding hydrochloric acid on the
strip of magnesium.
Mg(s) + 2HCl (aq) ------------> H2(g) + MgCl2(aq)
Magnesium Hydrochloric acid Hydrogen Magnesium chloride
Fe(s) + 2HCl (aq) ------------> FeCl2(aq) + H2(g)
Iron Hydrochloric acid Iron chloride hydrogen
Physical Properties:
It is colorless, odourless and tasteless. Lighter than other gases and
inflammable.

9. Chemical Properties:
1. Some of the reactive metals like sodium, potassium, calcium etc, react
with hydrogen and give hydrides of the metals.
2Na + H2 ------------> 2NaH
Sodium Hydrogen Sodium hydride
2. With the process of reaction of non metals with hydrogen, hydroxide of
non metals are produced.
Cl2 + H2 ---------------> 2HCl
Chlorine Hydrogen Hydrochloric acid
Uses of Hydrogen:
Hydrogen gas is used as fuel and also it is used to obtain electricity. It is
lighter than air, hence this gas is used in the balloons which are used for
the study of the atmosphere above air level.
To fill balloons and airships, as it is the least dense gas. Also used in the
synthesis of ammonia.
In hardening of vegetable and animal oils.

10. NITROGEN:
Nitrogen, N2 is a colorless odourless gaseous non-metallic main group
element which belong to Group Vb of the periodic table.
Preparation
1. Nitrogen is prepared by heating a mixture of mixture of ammonium
chloride and sodium nitite.
NH4Cl + NaNO2 ------------> NH4NO2 + NaCl
Ammonium chloride Sodium nitrite Ammonium nitrite Sodium chloride
NH4NO2 ------------> N2 ↑ + 2 H2O
Ammonium nitrite Nitrogen gas Water
Physical Properties:
It is colorless, odourless and tasteless. It is aneither combustible nor a
support of combustion.
Chemical Properties:
1. It combines with other elements in suitable circumstances and makes
compounds.
2. Nitrogen combines with Oxygen and forms nitric oxide. Combining with
more Oxygen it produces nitrogen dioxide.

11. N2 + O2 ------------> 2 NO
Nitrogen Oxygen Nitric oxide
2 NO + O2 -------------> 2 NO2
Nitric oxide Oxygen Nitrogen dioxide
Nitrogen dioxide dissolves in water and Nitric acid.
Uses to Nitrogen
1. It is used to prepare chemicals like Ammonia, Nitric acid, Calcium
Cyanamide, urea etc.
2. It is used to prepare inert atmosphere e.g. On the inflammable liquid,
instead of air, nitrogen gas should be filled so that there is less possibilityof
fire.
3. It decreases reactivity of oxygen (O2) in air and in films, dramas, to show
unnatural smoke or clouds, nitrogen gas is used.
4. The roots of the plants like peas make use of the nitrogen from the air
and produce food containing plenty of protein. It is filled in the tubes of the
tyres of some of the vehicles.