Oxi: Tính chất, ứng dụng và cách điều chế [Tổng hợp Lớp 8 + 10]

Accounting for 49.4% of the mass of the Earth's crust, oxygen is considered a common chemical element. This is also an important curriculum content in the Chemistry program at both middle and high school levels. The article below will help you synthesize important knowledge about the properties, preparation methods as well as important applications of this element in life.

What is the definition of oxygen?

Oxygen (English name is Oxygen) is a chemical element with the symbol O. The chemical formula of single element (gas) oxygen is O2; The atomic mass is 16 and the molecular mass is 32. Oxygen is known to be the common chemical element with the largest mass in the Earth's crust. In the form of elemental oxygen compounds found in sugar, water, ores, rocks, human and animal bodies…

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Oxygen has an atomic number of 8, belongs to group VIA, period 2 of the periodic table of chemical elements.

The oxygen atom has an electron configuration of 1s22s22p4, with an outer shell of 6e. Under normal conditions, an oxygen molecule has two atoms linked together by a nonpolar covalent bond. The structural formula of an oxygen molecule can be written as O=O.

Physical properties of oxygen

To clarify the physical properties of oxygen gas, chemistry textbook 8 (Vietnam Education Publishing House) has provided observation situations as well as questions to suggest knowledge for you to visualize more clearly.

Observation: There is a bottle of oxygen gas sealed. The learner's task is to comment on the color of oxygen gas. Next, uncork the bottle, bring it close to your nose and use your hand to gently flick oxygen into your nose to observe its smell.

The next 2 questions asked to learn about the properties of oxygen are:

• 1 liter of water at 20 degrees Celsius can dissolve 31 ml of oxygen gas. There are gases (for example ammonia) that dissolve 700 liters in 1 liter of water. So is oxygen gas more or less soluble in water?

• Determine whether oxygen is heavier or lighter than air? (Indicate that the density of oxygen to air is 32 : 29).

After answering the questions and observations above, we can easily conclude that the typical physical properties of oxygen gas are:

• Oxygen gas is a colorless, odorless, tasteless gas and heavier than air (d= 32/29, approximately equal to 1.1).

• Under atmospheric pressure, oxygen liquefies at a temperature of -183 degrees Celsius.

• Oxygen gas is slightly soluble in water. 100ml of water at 20 degrees Celsius, 1 atm can dissolve 3.1ml of oxygen gas.

• The solubility of oxygen gas at 20 degrees Celsius and 1 atm is 0.0043g in 100g of H2O.

Chemical properties of oxygen

Learning about oxygen cannot ignore its basic chemical properties. In general, oxygen is a very active nonmetal, especially at high temperatures, easily participating in chemical reactions with many nonmetals, metals and compounds. In chemical compounds, the element oxygen has valence II.

Oxygen reacts with metals

Chemistry Textbook Grade 8 gives an example of an experiment to prove that oxygen can react with metals as follows:

Take a small piece of iron wire and put it in a bottle of oxygen gas. Observe the experiment to see if any chemical reactions occur. Continue to wrap a piece of wooden charcoal around the end of the iron wire, burn until the iron and charcoal are red hot, then put it in a bottle containing oxygen. Through observation, we can draw the following conclusion: When putting an iron wire wrapped with a piece of ember into a bottle of oxygen, the piece of charcoal burns first, creating a temperature high enough for the iron to burn. Iron burns strongly and brightly without flame or smoke, creating small brown molten particles called iron (II, III) oxide, chemical formula Fe3O4 (magnetic iron oxide).

The chemical equation occurs as follows:

3Fe (r) + 2O2 (k) → Fe3O4 (Condition: Temperature)

Another example: Mg + O2 → 2MgO (Condition: Temperature)

Oxygen reacts with nonmetals

Perform an experiment by placing an iron spoon containing a small amount of sulfur powder into the flame of an alcohol lamp to observe. Continue to put burning sulfur into the bottle containing oxygen gas and compare the phenomenon of sulfur burning in oxygen and in air.

Observing the experiment, we can draw conclusions:

Sulfur burns in air with a small pale blue flame. When burned in air more intensely, it forms sulfur dioxide gas (or sulfur dioxide) and very little sulfur trioxide (SO3).

The combustion of sulfur in air and oxygen is represented by the following chemical equation:

S (r)+ O2 (k) → SO2 (k) (Condition: Temperature)

Carry out the experiment by adding an amount of red phosphorus to an iron spoon (red-brown solid, insoluble in water). Insert the iron spoon containing phosphorus into the oxygen bottle. Observe for signs of a chemical reaction. Burn red phosphorus in air, then quickly put it in a vial containing oxygen and compare the burning of phosphorus in air and in oxygen. Comment on the substances formed in the vial and the walls of the vial.

Through observation, we can easily draw conclusions: Phosphorus burns strongly in oxygen gas with a bright flame, creating dense white smoke that sticks to the walls of the vial in the form of a water-soluble powder. That white powder is phosphorus pentoxide, with the chemical formula P2O5.

We have the following chemical equation:

4P (r) + 5O2 (k) → 2P2O5 (r) (Condition: Temperature)

C + O2 → CO2 (Condition: Temperature)

Oxygen reacts with compounds

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In addition to its effects on metals and non-metals, its effects on compounds is also one of the important chemical properties of oxygen.

Methane gas (found in pond mud gas, biogas gas) burns in air due to the interaction with oxygen gas, emitting a lot of heat. We have PTHH:

CH4 (k) + 2O2 (k) → CO2 (k) + 2H2O (h) (Condition: Temperature)

2CO + O2 → 2CO2

C2H5OH + 3O2 → 2CO2 + 3H2O

See more: What is IoT? Properties and most common applications

How to prepare oxygen?

There are many ways to prepare oxygen, depending on its purpose. Below are the most common ways to prepare and produce oxygen in the laboratory and in industry!

Prepare oxygen in the laboratory

In the laboratory, oxygen gas is prepared by decomposing compounds that are rich in oxygen and less stable to heat such as KMnO4 (solid), KClO3 (solid)… For example:

2KMnO4 → K2MnO4 + MnO2 + O2 (Condition: Temperature)

Oxygen production in industry

There are two ways to produce oxygen in industry: from air and from water.

• Producing oxygen from air: After removing all water, dust, and carbon dioxide, the air is liquefied. Fractional distillation of liquid air will yield oxygen. Oxygen is transported in steel tanks with a capacity of 100 liters under a pressure of 150 atmospheres.

• Producing oxygen from water: Carrying out electrolysis of water (with a small amount of H2SO4 or NaOH dissolved in water to increase the water's electrical conductivity), we obtain oxygen gas at the anode and hydrogen gas at the cathode. PTHH is as follows:

2H2O → (electrolysis) 2H2 + O2 (k)

Application of oxygen in life

Oxygen gas plays an important role in human life as well as in the fuel combustion industry.

The role of oxygen in the life of humans and animals

Oxygen has many important applications, playing a decisive role in the lives of humans and animals. Every day, we need about 20-30m3 of oxygen to maintain life.

Firefighters, pilots and divers, when performing their duties, need to breathe oxygen contained in special tanks.

Application of oxygen in industry – fuel combustion

When fuels burn in oxygen, they create much higher temperatures than burning in air. Oxygen's industrial application in fuel combustion is also demonstrated through the manufacture of rock-breaking mines and liquid oxygen used to burn fuel in rockets. A fairly close application of oxygen in the iron and steel industry is blowing oxygen gas to create greater temperatures, improving the performance and quality of iron and steel.

Exercises about oxygen in Chemistry textbooks with detailed explanations

After you have mastered the basic theoretical knowledge about oxygen, start practicing and doing the exercises to understand the lesson faster. Below are a few exercises about oxygen in Chemistry Textbooks 8 and 10 timhieulichsuquancaugiay.edu.vn compiled with detailed explanations for your reference.

Exercises about oxygen in Chemistry Textbook Grade 8

Lesson 1 (Chemistry Textbook Grade 8, page 84)

Use appropriate words from the box to fill in the blanks in the following sentences:

Metals, nonmetals, very active, very active nonmetals, compounds.

Oxygen gas is a single element… Oxygen can react with many…, …, …

Suggested answer:

Oxygen gas is a very reactive nonmetal. Oxygen can react with many nonmetals, metals, and compounds.

Lesson 2 (Chemistry Textbook Grade 8, page 84)

Give examples to prove that oxygen is a very active element (especially at high temperatures).

Suggested answer:

Oxygen is a very reactive element (especially at high temperatures), for example:

3Fe + 2O2 → Fe3O4.

S + O2 → SO2.

Lesson 3 (Chemistry Textbook Grade 8, page 84)

Butane has the formula C4H10 when burned, creating carbon dioxide and water vapor, and giving off a lot of heat. Write the chemical equation to represent the combustion of butane.

Suggested answer:

Chemical equation:

2C4H10 + 13O2 → (temperature) 8CO2 + 10H2O

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Lesson 4 (Chemistry Textbook Grade 8, page 84)

Burning 12.4g of phosphorus in a tank containing 17g of oxygen gas forms diphosphorus pentoxide P2O5 (a white solid).

a) Which phosphorus or oxygen substance is left over and how many moles of the substance are left over?

b) What substance is formed? What is the volume?

Suggested answer:

a) We have nP = 12.4/31 = 0.4 (mol); nCO2 = 17/32 = 0.53 (mol).

4P + 5O2 → 2P2O5

Considering the ratio of the number of moles in the problem to the number of moles in the equation of P and O2, we have:

0.4/4 P reacts completely with excess O2 reaction.

nO2 p = 5/4 x nP = 0.5 (mol).

Determine residual nO2 = 0.53 – 0.5 = 0.03 (mol).

b) The substance formed is phosphorus pentoxide P2O5.

We have nP2O5 = ½ x nP = 0.4/2 = 0.2 mol

mP2O5 = nM = 0.2 x (31x 2 + 16 x 5) = 28.4 (g).

Exercises about oxygen in Chemistry Textbook Grade 10

Exercise 1 (Chemistry textbook grade 10, page 127)

Match the electron configuration with the appropriate atom.

Electron configuration: A. 1s22s22p5; B. 1s22s22p4; C. 1s22s22p63s23p4; D. 1s22s22p63s23p5

Atomic: a/ Cl; b/ S; c/O; d/F

Suggested answer:

A – d; B – c; C – b; D – a.

Lesson 2 (Chemistry Textbook 10, page 127)

Which substance has a nonpolar covalent bond?

A. H2S; B. O2; C. Al2S3; D. SO2.

Suggested answer:

B. O2

Lesson 4 (Chemistry Textbook 10, page 127)

Present methods for preparing oxygen gas in the laboratory and in industry. Why not apply the method of preparing oxygen gas in the laboratory to industry and vice versa?

Suggested answer:

Preparing oxygen in the laboratory:

In the laboratory, oxygen is prepared by decomposing compounds rich in oxygen and low in heat with heat such as KMnO4, KClO3, …

2KMnO4 → K2MnO4 + MnO2 + O2

2KClO3 → 2KCl + 3O2

Oxygen preparation in industry:

There are 2 production methods:

• Producing oxygen from air: The air, after removing all water, dust, and carbon dioxide, is liquefied. Fractional distillation of liquid air will yield oxygen. Oxygen is transported in steel tanks with a capacity of 100 liters under a pressure of 150 atmospheres.

• Producing oxygen from water: By electrolysis of water (water with a small amount of H2So2 or NaOH dissolved to increase the water's electrical conductivity), we obtain oxygen gas at the anode and hydrogen gas at the cathode. PTHH is as follows:

2H2O → (electrolysis) 2H2 + O2 (k)

The two processes cannot be interchanged because industrial preparation requires a large amount of oxygen at a low cost, while in the laboratory only a small amount is needed.

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