Oxygen 6r1h23

aboratory Preparation of Oxygen Any of the above mentioned methods could be used to prepare oxygen in the laboratory. Mercuric and silver oxides are not used for the preparation of oxygen, as they are very expensive. For the laboratory preparation of oxygen from any of the compounds like lead dioxide, trilead tetroxide, potassium nitrate, sodium nitrate, potassium chlorate or potassium permanganate, the arrangement of apparatus is, as per the diagram (Fig.13.7).

Oxygen is usually collected over water because the solubility of the gas in water is not high. If the gas is needed dry, then it can be ed through a drying agent, like anhydrous calcium chloride or quick lime, or concentrated sulphuric acid, and then collected over mercury.

Lab preparation of oxygen To prepare oxygen; you would need the following apparatus: 1.Test tubes 2.Manganese (IV) dioxide (MnO2) 3. Hydrogen peroxide (it must be fresh and kept away from light)(H2O2) 4. Wooden splinter (only needed if you are going to check how oxygen helps in combustion). 5.Candle and matchsticks.

Method: 1.First, take the test tube and put a little bit of MnO2 (Manganese dioxide) 2. At this time, you will need a friend's or someone else's help (only if you are requiring it to check how oxygen helps in combustion). First, tell your friend to light the candle and to ignite the splinter using the candle. At that time, take a small amount of hydrogen peroxide in a beaker or test tube. Then, tell him/her to to bring the wooden splinter close to the test tube. As soon as he/she brings it, put a little bit of hydrogen peroxide (not more than 1ml). You should see the reaction forming a gas, which looks like smoke. This gas is Oxygen. 3. What happens to the splinter when you bring it close to Oxygen? Of course! The splinter burns more brightly and intensely. 4. Should you want to only collect Oxygen, you need not do the second part of the second step. Precautions: 1. Do not drop the test tubes. 2. Always wear gloves while performing chemical experiments. 3. Always wear lab coats while doing the same. 4. Do NOT eat or manganese oxide or rub them on your eyes. Serious problems may occur, which even might result in blindness or death. 5. Do NOT put warmed hydrogen peroxide on your skin. You might get a boil. 6. Never stand too close to the test tube. 7. If you are untrained, always seek for someone who is better at you in performing lab experiments, or anyone who already has done the lab preparation of Oxygen. 8. Keep H2O2 and MnO2 away from children.

9. If Oxygen gets into your eyes and you get an irritation, wash your eyes with cold water immediately.

What is the balanced equation for the laboratory preparation of oxygen? and why is water displacement method used in collecting oxygen? pls. explain.. need help in this.. Method 1 - Decomposition of H2O2 using MnO2 catalyst 2H2O2 --MnO2--> O2(g) + 2H2O(l) Method 2 - Decomposition of potassium chlorate 2KClO3(s) --> 2KCl(s) + 3O2(g) Method 3 - Electrolysis of water 2H2O --electricity--> 2H2(g) + O2(g) http://www.chemistryland.com/CHM130FieldLab/Lab7/Lab7.html

When required in tonnage quantities, oxygen is prepared by the fractional distillation of liquid air. Of the main components of air, oxygen has the highest boiling point and therefore is less volatile than nitrogen and argon. The process takes advantage of the fact that when a compressed gas is allowed to expand, it cools. Major steps in the operation include the following: (1) Air is filtered to remove particulates; (2) moisture and carbon dioxide are removed by absorption in alkali; (3) the air is compressed and the heat of compression removed by ordinary cooling procedures; (4) ... (100 of 1,727 words)

Oxygen gas is "collected over water" in order to produce "pure" oxygen. It is contaminated only with water vapor. It works because oxygen is not very soluble in water.

Preparation of Oxygen Preparation of Oxygen from Potassium Trioxochlorate(V) The most common laboratory method of preparation of oxygen gas is by heating a mixture of potassium trioxochlorate(V), KClO3, and manganese(IV) oxide, MnO2, in a test tube. The potassium trioxochlorate(V) is decomposed in the presence of the heat to form potassium chloride, KCl, and the oxygen gas, O2. 2KClO3(s) + heat → 2KCl(s) + 3O2(g)

The oxygen formed may be collected as either  

Wet Oxygen – The oxygen is collected over water or Dry Oxygen – The oxygen oxygen is collected over mercury Oxygen gas formed may be transferred to the bottom of a water trough and collected at the top of an inverted glass cylinder as wet oxygen. The oxygen from the heated test tube may also be conveyed via a delivery tube to a U-tube containing anhydrous calcium chloride. The anhydrous calcium chloride is a drying agent that removes moisture from the oxygen gas so that dry oxygen is formed. The dry oxygen is finally delivered via another delivery tube into a glass saucer containing mercury and collected at the top of an inverted test tube on the mercury. Preparation of Oxygen from Hydrogen Peroxide Solution Another laboratory preparation of oxygen is the preparation from hydrogen peroxide in the absence of heat by,

 

Decomposition in the presence of manganese(IV) oxide, MnO 2, catalyst and Oxidation in the presence of potassium tetraoxomanganate(VII), KMnO4.Preparation of Oxygen from Air

Commercial methods

All About Oxygen Oxygen, O2, is a colourless odourless gaseous main group element which belong to Group VIb of the periodic table.     

Atomic Number : 8 Atomic Mass : 15.9994 Melting Point : -214 degC Boiling Point : -183 degC Density : 1.429

Atmospheric oxygen is of vital importance for all aerobic organisms. For industrial purposes, oxygen is obtained by fractional distillation of liquid air. It is used in metallurgical processes, in high-temperature flames and in breathing apparatus.

Occurrence of Oxygen: Oxygen occurs in the free state as a gas, to the extent of 21 per cent by volume or 23 per cent by weight in the atmosphere. Combined Oxygen also occurs    

in water, in vegetable and animal tissues, in nearly all rocks and in many minerals.

Oxygen occurs to a larger extent in the earth's crust than any other element.

Laboratory Preparation of Oxygen: Because oxygen is a component of air, it has been studies extensively over the centuries and there is a large number of different methods for its 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. Preparation of oxygen Using potassium chlorate

Potassium chlorate decomposes at a low temperature if previously mixed with manganese dioxide which is a catalyst for the decomposition. Only the potassium chlorate is decomposed, and no perchlorate is formed : 2 KClO3

==>

2 KCl

+

3 O2

Other methods in preparing oxygen: Preparation of oxygen using hydrogen peroxide

The decomposition of hydrogen peroxide using manganese dioxide as a catalyst also results in the production of oxygen gas. 2 H2O2

==>

2 H2O

+

O2

Preparation of oxygen by the chemical decomposition of water

Oxygen is obtained from water by ing a mixture of steam and chlorine through a strongly heated silica tube containing pieces of broken porcelain. 2 H2O

+

2 Cl2

==>

4 HCl

+

O2

The hydrogen chloride is removed by a wash-bottle containing sodium hydroxide solution and the Oxygen collected over water. Preparation of oxygen By decomposition of oxides

Oxygen may be obtained by heating some metallic oxides. 

  

  

  

When mercuric oxide is strongly heated in a hard glass tube, it decomposes, globules of mercury collect in the cooler part of the tube and oxygen gas is evolved. It may be collected over mercury in a pure and dry state. 2 HgO

==>

2 Hg

+

O2

Silver oxide decomposes at a lower temperature than mercuric oxide. When the silver oxide is prepared by precipitation from a solution of silver nitrate by a solution of pure potassium hydroxide in absence of atmospheric carbon dioxide the silver oxide formed gives very pure oxygen. 2 Ag2O

==>

4 Ag

+

O2

Many higher oxides of metals decompose on heating forming the lower oxides and oxygen gas. o 2 BaO2 ==> 2 BaO + O2 o 3 MnO2 ==> Mn3O4 + O2 o 2 PbO4 ==> 6 PbO + O2 o 2 PbO2 ==> 2 PbO + O2 Manganese dioxide evolves oxygen more readily when heated with concentrated sulphuric acid. 2 MnO2

+

2 H2SO4

==>

2 MnSO4

+

2 H2O

+

O2

Preparation of oxygen by the decomposition of salts

Some salts containing oxygen decompose and release oxygen gas on heating. 



Potassium nitrate melts on heating and at a slightly high temperature decomposes, giving off bubbles of oxygen and forming potassium nitrite which solidifies on cooling.

 

2 KNO3

==>

  

+

O2

Potassium chlorate crystals melt when heated in a hard glass tube at 360 degC and then decompose to form potassium chloride and releasing oxygen.

  

2 KNO2

2 KClO3

==>

2 KCl

+

3 O2

Potassium permanganate which is a purple crystalline solid, decomposed without fusing on heating to 240 degC, forming a black powder consisting of a mixture of potassium manganate and manganese dioxide and releasing oxygen. 2 KMnO4

==>

K2MnO4

+

MnO2

+

O2

Potassium permanganate explodes violently when heated with concentrated sulphuric acid. However, when a solution of hydrogen peroxide is mixed with a solution of the permanganate and diluted sulphuric acid added, the two compounds decompose together, forming a nearly colourless solution, and oxygen is evolved.

 

2 KMnO4

+

3 H2SO4

+

5 H2O2

==>

K2SO4

+

2MnSO4

+

8H2O

+5O2 

Chromic trioxide which is a red crystalline solid, melts on heating at about 420 degC, leaving a green residue of chromic oxide and evolves oxygen.

  

4 CrO3

  

==>

2 Cr2O3

+

3 O2

Potassium dichromate which is a bright-red crystalline solid, melts on heating and when strongly heated releases oxygen leaving a mixture of yellow potassium chromate which is soluble in water, and green chromic oxide, which is insoluble in water. 4 K2Cr2O7

==>

4 K2CrO4

+

2 Cr2O3

+

3 O2

Chromium trioxide and potassium dichromate when heated with concentrated sulphuric acid forms chromic sulphate and releases oxygen.

   

4 CrO3 2 K2Cr2O7

+

+

6 H2SO4

10H2SO4

==>

==>

2 Cr2(SO4)3

4 KHSO4

+

+

6 H2O

2 Cr2(SO4)3

+

+3 O2 8 H2O

+3 O2

Preparation of oxygen from air

Oxygen may be obtained from the atmosphere in a chemical process, by heating mercury in a confined volume of air, when the oxygen reacts with the mercury to form mercuric oxide. The mercuric oxide so formed is then heated strongly, when it decomposes and pure oxygen is evolved.

In a similar process, if yellow lead monoxide is carefully heated in an iron dish and freely exposed to air, it takes up oxygen from the air and forms red lead. 6 PbO + Yellow Lead Monoxide

O2

==> Red Lead

2 Pb3O4

On heating strongly, the red lead decomposes into lead monoxide and Oxygen gas which is evolved. 2 Pb3O4

==>

6 PbO

+

O2

Commercial Preparation of Oxygen

One commercial method of preparing oxygen involves the electrolysis of water, which consists of breaking up the water compound by the means of an electric current. A dilute acid, such as sulfuric acid, is added to the water to make it a conductor of electricity. Direct current is then ed through the solution, and the water is decomposed into oxygen and hydrogen gases. The oxygen collects in a water tube containing the positive (+) electrode (anode) at the hydrogen collects in a water tube containing the negative (-) electrode (cathode). 2H2O → H2↑ + O2↑ Another commercial method involves the distillation of liquid air. When air is applied with high pressure and low temperature, it can be liquefied. As it is allowed to warm up, nitrogen—which has a lower boiling point than oxygen—escapes as a gas, leaving nearly pure oxygen as a liquid. It can then be stored either as a liquid or as a compressed gas in metal containers.

Industrial Preparation of Oxygen The industrial method of making oxygen involves two stages:

 

Liquefaction of air and Fractional distillation of liquid air. Liquefaction of air Gaseous air is initially ed through caustic soda to remove carbon(IV) oxide and then delivered into a compressor operating at a pressure of 200 atm where it is cooled and allowed to escape rapidly through a minute aperture into a low pressure chamber to form liquid air. The liquid air is then delivered to a fractionating column to undergo fractional distillation. Fractional distillation of liquid air Here, the liquid oxygen is distilled to evolve, first, nitrogen at a boiling point of -196°C leaving behind oxygen-rich liquid. The liquid is further heated to -183°C to form gaseous oxygen which is dried, compressed and stored under pressure (at 100 atm) in steel cylinder.

Summary Oxygen is a colorless gas that is essential for life. It is slightly soluble in water and also s water-borne life. Oxygen combines with many other elements by the process of oxidation. It is the most abundant element found on the Earth and makes up 21% of the atmosphere. As a compound, oxygen is present in water, living things, and much of the solid material that makes up the earth. Oxygen can be prepared by heating certain oxygen compounds, through electrolysis or by liquefying air.