Chemistry 8 Lesson 24: Properties of oxygen
1. Summary of theory
1.1. Physical properties
– A gas, colorless, odorless, slightly soluble in water, heavier than air. Liquefaction at -1830C.
1.2. Chemical properties
a. Effect on nonmetals
Reaction with sulfur (S)
– How to proceed: Place an iron ladle containing S powder into the flame of an alcohol lamp. Then put the burning S into a glass jar containing oxygen gas.
Video 1: The reaction between sulfur and oxygen gas
– Phenomena: Sulfur burns more intensely in oxygen than in air, giving a blue flame.
– Explain: Because sulfur burns in oxygen to form sulfur dioxide (SO2), also known as sulfur gas) and very little sulfur trioxide (SO3)
– Reaction equation: S + O2 → SO2
Effects with Phosphorus
– How to proceed: Burning Red Phosphorus in Oxygen
Video 2: Phosphorus burns in oxygen gas
– Phenomena: Phosphorus burns vigorously in oxygen with a bright flame, producing dense white smoke that adheres to the walls of the vial as a water-soluble powder.
– Explain: The white powder formed at the bottom of the vial is phosphorus pentaoxide with the chemical formula P .2O5
– Chemical equation: 4P + 5O2 → 2P2O5
b. Effect with metal
– How to proceed: Add a piece of charcoal to the iron wire (the purpose is to provide heat for the iron wire thanks to the combustion reaction of Carbon) and then burn the iron wire red hot and then put it into an oxygen tank.
Video 3: Iron burns in oxygen gas
– Phenomena: When the iron wire wrapped with embers is placed in the oxygen cylinder, the piece of coal burns first, creating a temperature high enough for the iron to burn. Iron burns strongly, brilliantly, without flame, without smoke, producing small brown molten particles.
– Explain: Small brown molten particles are Iron(II, III) oxide, chemical formula is Fe3O4 commonly known as ferromagnetic oxide.
– Reaction equation: 3Fe + 2O2 → Fe3O4
c. Effects with compounds
Methane gas is present in pond sludge, the combustion reaction of methane in the air to form carbon dioxide and water, and at the same time give off a lot of heat.
ONLY4 + 2O2 → HAVE2 + 2 HOUSES2O
2. Illustrated exercise
2.1. Form 1: Write a chemical equation
Write a mathematical equation to represent the combustion reaction in oxygen of:
a) Nonmetals: C, S, P. Know that P forms P2O5.
b) Metals: Na, Zn, Al, Fe, Cu. Knowing Fe forms Fe3O4.
c) Compounds: CO, NO, ON4,2H6,3H8, know CO and NO when burned in oxygen to form CO2 and NO2, the remaining compounds form CO . gas products2 and steam.
a. The equations of the reaction taking place are:
C + O2 → CO2
S + O2 → SO2
4P + 5O2 → 4P2O5
b. The equations of the reaction taking place are:
4Na + O2 → 2Na2O
2Zn + O2 → 2ZnO
4Al + 3O2 → 2Al2O3
3Fe + 2O2 → Fe3O4
2Cu + O2 → 2CuO
c. The equations of the reaction taking place are:
2CO + O2 → 2CO2
2NO + O2 → 2NO2
ONLY4 + 3O2 → CO2 + 2 HOUSES2O
2 C2H6 + 7O2 → 4CO2 + 6 HOUSES2O
C3H8 + 5O2 → 3CO2 + 4 HOURS2O
2.2. Form 2: Calculate according to the chemical equation
Complete combustion of 20 dm3 of acetylene gas (C2H2) contains 3% non-combustible impurities.
a. Write the equation for the combustion reaction.
b. Calculate the volume (dktc) of oxygen gas needed.
c. Calculate the mass of carbon dioxide gas and the mass of water formed.
a. The combustion reaction equation:
2 C2H2 + 5O2 → 4CO2 + 2 HOUSES2O
b. 2 C2H2 + 5O2 → 4CO2 + 2 HOUSES2O
2 5 4 2
0, 87 → 2.175 → 1.74 → 0.87
1 dm3 = 1 liter
C gas2H2 purity accounted for 97%.
Gas volume C2H2 pure:
(20.97): 100 = 19.4 liters
Molar C2H2 pure:
n = VC2H2: 22.4 0.87 mol
Oxygen gas volume (dktc): VO2 = nO2.22.4 2,175.22.4 = 48.72 liters
c) Mass of CO2: mCO2 = nCO2. MCO2 = 1.74. 44 = 76.56 g
Volume of water: mH2O = nH2O. MH2O = 0.87. 18 = 15.66 g
2.3. Form 3: Math form about impurities
People prepare quicklime CaO by heating limestone CaCO3. The amount of quicklime obtained from 1 ton of limestone containing 10% impurities is how many tons? Know the main component of limestone is CaCO3.
We have: (1.90): 100 = 0.9 tons = 900 kg
CaCO3 → CaO + CO2
100 (g) 56 (g)
900 (kg) x (kg)
Mass of CaO obtained:
x = (900.56) : 100 = 504 (kg)
3.1. Essay exercises
Question 1: Burning 3.1 g of phosphorus in an oxygen tank produces diphosphate pentaoxide. Calculate the mass of oxide obtained
Verse 2: Let 0.56 g Fe react with 16 g oxygen to produce ferromagnetic oxide. Calculate the mass of ferromagnetic oxide and indicate the residue left after the reaction
Question 3: Calculate the volume of oxygen gas that reacts when 3.6 g C . is burned
Verse 4: Burning sulfur in oxygen, after the reaction, 4.48 liters of sulfur trioxide gas are obtained (dktc).
a) Write the equation for the reaction.
b) Calculate the mass of sulfur participating in the combustion reaction.
c) Calculate the volume (dktc) of oxygen needed for the reaction to take place completely.
Question 5: Complete combustion of 17.6 g of propane (C3H8) in the air.
a) Calculate the volume of carbon dioxide gas obtained after the reaction (dktc).
b) Calculate the volume of water formed.
3.2. Multiple choice exercises
Question 1: How many times heavier is oxygen than air?
A. 1.1 times
B. 0.55 times
C. 0.90625 times
D. 1,8125 times
Verse 2: Strong, bright, smoke-free fire is a reaction phenomenon
A. C+O2 → CO2
B. 3Fe+2O2 → Fe3O4
C. 2Cu+O2 → 2CuO
D. 2Zn+O2 → 2ZnO
Question 3: Burning in oxygen with a small flame has a light blue color, burning in air is more intense than a reaction phenomenon
A. 2S + 3O2 → 2SO3
B. S + O2 → SO2
C.P + O2 → P2O5
D.P + O2 →P2O5
Verse 4: Burns vigorously in oxygen with a bright flame, produces dense white smoke that adheres to the walls of the vial in the form of a water-soluble powder that is the reaction
A. 4P + 5O2 → 2P2O5
B.P + O2 → P2O3
C. S + O2 →SO2
D. 2Zn + O2 →2 ZnO
Question 5: Choose the correct answer
A. Oxygen is not able to combine with hemoglobin in the blood
B. Oxygen gas is a very active metal element
C. Oxygen is heavier than air
D. Oxygen has 3 valences
After the lesson to know:
- Elemental oxygen, about the nonmetallic element oxygen? What do you think about the color, taste and water solubility of oxygen gas?
- Can oxygen react with other substances? If yes, is it strong or weak?