[Chemistry Class Notes] on Dioxygen Pdf for Exam

Dioxygen, one of the common allotropes of elemental oxygen, and it is represented with the chemical formula O₂. It is generally known as oxygen, but to avoid confusion with elemental oxygen, it is also called dioxygen, molecular oxygen, or oxygen gas. Oxygen gas reacts with almost all the elements with the exception of noble gases. The resulting compound is known as oxides. Oxygen gas is very important for combustion, though it is not flammable on its own. It is also a life-giving gas as mammals breathe in oxygen to live, as it helps to release energy.

Laboratory Preparation of Dioxygen

There are numerous ways of preparing dioxygen in the laboratory.

1. Catalytic decomposition of Sodium Potassium Chlorate with Magnesium dioxide as the catalytic produces dioxygen.

[ 2KClO_{3}  rightarrow  2KCl + 3O_{2} ]

This reaction occurs on heating, in the presence of MnO₂ at 420K.

2. Thermal decomposition of metal oxides with relatively low electrode potential in the electrochemical series like that of Mercury and Silver oxides etc. produces Dioxygen.

[2HgO (s) rightarrow 2Hg (l) + O_{2} (g)]

[ 2PbO_{2} (s) rightarrow 2PbO (s) + O_{2} (g) ]

3. Salts rich in oxygen, like nitrates and permanganates, produce Dioxygen when decomposed thermally.

[ 2KNO_{3} rightarrow 2KNO_{2} + O_{2} ]

[ 2KMnO_{4} rightarrow K_{2}MnO_{4}  + MnO_{2} + O_{2} ]

[2NaNO_{3}  rightarrow 2NaNO_{2}  + O_{2} ]

4. The decomposition of Hydrogen Peroxide also produces oxygen and to increase the rate of decomposition, manganese(IV) oxide is added as a catalyst. 

[2H_{2}O_{2}(aq) rightarrow 2H_{2}O(l) + O_{2} (g)]

Industrial Production of Oxygen

There are two primary methods used for the industrial production of O₂ from the air.

1. Fractional distillation of liquified air with N₂  distilling as a vapor while O₂ is left as a liquid. Here liquid air is a mixture of liquid Nitrogen and liquid Oxygen. Nitrogen is more volatile because of the lower boiling point. It boils up first, leaving behind the pure oxygen. 

2. Another method includes passing clean, dry air through one bed of a pair of zeolite molecular sieves, which absorbs the N₂ gas, and delivers the gas which is 90%-93% oxygen.

 

Physical Properties of Dioxygen

• It’s an odorless, colorless, and tasteless gas.

• It is heavier than air with a density of 1.429 g/L.

• It is slightly soluble in water, which is just sufficient to support aquatic life.

• The melting point of oxygen is around 54.36 K and the Boiling point is around 90.188 K.

• Oxygen exists in all three forms, i.e solid, liquid, and gas depending upon the temperature and pressure. 

Chemical Properties

[4Na + O_{2} rightarrow 2Na_{2}O ](With Metal)

[C + O_{2} rightarrow CO_{2} ](With Non-metal)    

• It is paramagnetic in nature.

• Oxygen normally does not react with acids and bases. 

• Oxygen is a good oxidant and hence supports combustion. 

[Fuel + O_{2} rightarrow CO_{2} + H_{2}O]

Example,   CH₄ + O₂ ⟶ CO₂ + H₂O

[Fe  + O_{2}+ H_{2}O  ⟶ Fe_{2}O_{3}n.H_{2}O ](Hydrated Iron Oxide)

Uses of Dioxygen

• Dioxygen is vital for the respiration process.

• It is used in oxygen cylinders which are used in hospitals and for mountaineering.

• It is used for welding and cutting metals in the form of oxy-acetylene.

• Oxygen gas combines with acetylene gas and produces an oxy-acetylene flame used for cutting and welding metals.

• It is used in rocket fuel in liquid form. 

• It is used in the production of Nitric acid.

• It is used for artificial respiration mixed with Carbon dioxide or methane.

• Oxygen is used in laser cutting. 

• Oxygen is used in combustion processes. Materials that do not normally burn in air, burn easily in oxygen, so mixing oxygen with air enhances the combustion process. 

• Oxygen is used in water treatment processes, for purifying wastewater and treating sewage.

Fun Facts About Dioxygen

1. 21 % of the earth’s atmosphere is made up of oxygen gas.

2. Warm water holds less dissolved oxygen than cold water because molecules are moving faster in warm water than cold water which allows oxygen to escape from the water. 

3. The liver consumes the highest oxygen in the human body. 

4. The health level of the water is measured by its oxygen gas content.

5. Pure oxygen is toxic. We can’t inhale 100 % Oxygen gas. In reality, we inhale air which is 21% oxygen. 

6. The mass of the sun is made up of around 1% Oxygen. 

7. Oxygen is essential for our respiratory system, whereas its allotrope ozone (O₃) is highly toxic. 

Conclusion

In the above-given information, ’s expert team has described Dioxygen – Preparation, Properties, and Uses which are to be studied by the students to provide and get the best result in the examination. Candidates appearing for chemistry examination should know that Dioxygen is an important chapter that has a good weightage and question based on this topic can be of any type multiple choice question, very short answer question, short answer question or long answers question, therefore students should prepare accordingly so that they are able to write answers properly and get prepared for the examination.

To study this chapter properly students should cover everything about these like dioxygen -preparation, properties and uses. Candidates can get involved in the studies with the help of ’s experts and get a better understanding of all the topics. Candidates should also study the important questions and the sample papers to get ready for the examination. Chemistry needs learning of the formulas so students can prepare revision notes for all the formulas and study thoroughly to get a command in the formulas of Chemistry.