"Preparing Oxygen" Air Around Us PPT Courseware 6

"Preparing Oxygen" Air Around Us PPT Courseware 6

catalyst:

A substance that can change the reaction rate of other substances in a chemical reaction, but its own quality and chemical properties do not change before and after the chemical reaction is called a catalyst (also called a catalyst)

in chemical reaction

"One change": changing the reaction rate of other substances

"Two unchanged": its own quality and chemical properties remain unchanged

Remark

1. The catalyst cannot determine the occurrence and stop of the reaction.

2. Cannot increase or decrease the quality of the product

3. Manganese dioxide does not act as a catalyst under all circumstances.

Catalysis: The role of catalysts in chemical changes is called catalysis

practise:

Which of the following statements about catalysts is correct ( )

A. A substance that accelerates the reaction rate of other substances in a chemical reaction without changing its quality and properties before and after the chemical reaction is called a catalyst.

B. Manganese dioxide is a catalyst

C. A substance that changes the reaction rate of other substances in a chemical reaction but does not change its mass and chemical properties before and after the chemical reaction is called a catalyst.

D. In order for the hydrogen peroxide solution to decompose into oxygen, manganese dioxide must be added, otherwise the decomposition reaction cannot occur.

5. Things to note:

1. When fixing the test tube, why should the mouth of the test tube be slightly lower than the bottom of the test tube?

Prevent condensed water from flowing back to the bottom of the hot test tube and bursting the test tube

2. When should we start collecting using the drainage and gas collection method?

Start collecting when the bubbles are released continuously and evenly;

(Which method obtains purer oxygen? The gas collected by the drainage method is purer)

3. At the end of the experiment, should the tube be moved away from the water first or should the heating be stopped first? Why?

Move the conduit away from the water first, and then stop heating, otherwise the water will flow back along the conduit back to the bottom of the heated test tube and burst the test tube.

4. When using potassium permanganate to produce oxygen, why is it necessary to plug a ball of cotton into the mouth of the test tube?

Can prevent potassium permanganate powder from entering the catheter during heating

practise:

1. The method to identify oxygen is: put a wooden stick with sparks into the gas collecting bottle. If the wooden stick ignites again, it proves that the gas is oxygen.

The way to check that the oxygen is full is to place a wooden stick with sparks on the mouth of the gas collecting bottle. If the wooden stick ignites again, it proves that full oxygen has been collected.

The method to identify carbon dioxide is: inject clear lime water into the gas collecting bottle. If the lime water turns turbid, it proves that the gas is carbon dioxide.

The way to check that the carbon dioxide is full is to put a burning wooden stick on the mouth of the gas collecting bottle. If the wooden stick goes out, it proves that the carbon dioxide has been collected.

2. The picture on the right is a diagram of the device for producing and collecting oxygen using potassium permanganate in the laboratory:

(1) Point out the name of the instrument with a label in the picture

(2) During the experiment, please pay attention to: ① The mouth of the test tube must be ____________; its purpose is ____________________________;

②When heating the test tube, ____ first, and when stopping heating, ____________ first and then __________ to avoid __________________.

(3) The above method of collecting gas is called ________. How to make the collected gas basically free of nitrogen? ____________________.

(4) Using the above device to produce gas should meet the following conditions _____ (fill in the serial number)

A. The reactants are all solid B. The reaction requires heating C. The gas produced is not easily soluble in water D. The gas produced is denser than air

Student experiments:

1. Inventory experimental instruments and medicines;

2. Organize the experimental bench;

3. Experiment

Check:

Installation: Use a paper trough on the sink to add potassium permanganate and stuff it with cotton

Solid: The mouth of the test tube should be slightly lower than the bottom of the test tube

Add: Use external flame to heat the medicine from front to back

Collection and drainage method: extend the mouth of the conduit to the mouth of the gas collecting bottle

Upward emptying method: The pipe mouth is extended to the bottom of the gas collecting bottle

Move: Move the catheter out of the water first

Extinguish: extinguish the alcohol lamp

4. Disassemble and clean instruments, organize experimental benches, and count instruments

1. Through recent study and information review, students in the extracurricular activity group summarized the following methods of producing oxygen:

A. Electricity decomposes water: H2O Electricity H2 ↑ + O2 ↑

B. Heating potassium chlorate to decompose: KClO3 KCl + O2 ↑

C. Heating potassium permanganate to decompose: KMnO4 △ K2MnO4 + MnO2 + O2↑

D. Decomposition of mercury oxide by heating: HgO △ Hg + O2 ↑

E. Catalytic decomposition of hydrogen peroxide: H2O2 MnO2 H2O + O2 ↑

Please discuss with your classmates in the extracurricular activity group, laboratory

What is the best way to produce oxygen and why?

Plan E is the best. Because Plan E has the advantages of safety, simplicity, environmental protection, energy saving, and easy recovery of manganese dioxide.

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