"Preparing Oxygen" Life-Sustaining Gas - Oxygen PPT Courseware 3

"Preparing Oxygen" Life-Sustaining Gas - Oxygen PPT Courseware 3

Learning Content

Oxygen laboratory preparation method

Checking the air tightness of the device

Catalysts and catalysis

decomposition reaction

Industrial production of oxygen - separation of liquid air

1. Laboratory preparation method of oxygen

1. Medicines

Hydrogen peroxide (colorless liquid) Common name: hydrogen peroxide

H2O2

Manganese dioxide (black solid)

MnO2

Potassium permanganate (dark purple solid)

KMnO4

2. Reaction principle

Produce oxygen by decomposing hydrogen peroxide solution or heating potassium permanganate

Will wooden strips with sparks re-ignite when hydrogen peroxide is not heated?

When heating hydrogen peroxide, will the wood strips with sparks re-ignite?

Without heating, if manganese dioxide is added to hydrogen peroxide, will it re-ignite?

catalyst

Catalyst: A substance that can change the rate of chemical reactions of other substances without changing its own quality and chemical properties before and after the chemical reaction.

Catalysis: The role of catalysts in chemical reactions

Catalysts should be mastered

① It can change the reaction rate of other substances. The "change" here includes two meanings: speeding up and slowing down.

②The chemical properties of the catalyst do not change before and after the chemical reaction, but the physical properties may change.

③ Catalysts are for specific reactions. For example, manganese dioxide can act as a catalyst when hydrogen peroxide is decomposed to produce oxygen. However, manganese dioxide is not a catalyst for all chemical reactions.

④In a certain chemical reaction, different substances can be selected as catalysts. For example, when hydrogen peroxide is decomposed to produce oxygen, either manganese dioxide or iron oxide can be used as the catalyst.

decomposition reaction

The reaction in which one substance produces two or more other substances is called a decomposition reaction.

The type of decomposition reaction can be expressed concisely by the following general formula: AB→A+B+…

It can be referred to as "one becomes many".

5. Operation steps

first step

Check the air tightness of the device

Immerse one end of the tube into the water and place your hands against the outer wall of the test tube. If the device does not leak, the air inside will expand when heated and bubbles will appear at the mouth of the tube. Release your hands and allow it to cool. A column of water will form in the tube.

Step 2

Put the medicine into the test tube and plug the test tube tightly with the rubber stopper with the catheter

The medicine should be spread flat on the bottom of the test tube and heated evenly

third step

Secure test tubes and other instruments

Precautions

① The mouth of the test tube should be slightly tilted downward to prevent the moisture in the medicine from turning into water vapor when heated, and then condensing into water droplets and flowing back to the bottom of the test tube, causing the test tube to burst.

② The rubber stopper can be slightly exposed in the tube inside the test tube to facilitate gas discharge.

③When using potassium permanganate to produce oxygen, a ball of cotton should be placed at the mouth of the test tube

④The iron clamp should be clamped 1/3 away from the mouth of the test tube.

2. Decomposition reaction

Compare the following three chemical reactions and find out what they have in common:

�1. Hydrogen peroxide → water + oxygen

�2.Potassium permanganate→potassium manganate+manganese dioxide+oxygen

�3. Potassium chlorate → potassium chloride + oxygen

From the number of types of reactants and products, let's take a look at what they have in common. There is only one type of reactant but there are multiple types of products.

Decomposition reaction: A reaction in which two or more new substances are produced from one substance.

General formula: AB→A+B

Features: Pay attention to one "point", changing from one to many

Note the difference between decomposition reactions and combination reactions. . . .

3. Industrial production method of oxygen

industrial manufacturing

Industrial production of large amounts of oxygen is achieved by separating liquid air (physical change)

The air is pressurized at low temperatures to convert it into liquid air, which then evaporates. Since the boiling point of liquid nitrogen is lower than that of liquid oxygen, the nitrogen evaporates first from the liquid air, leaving mostly liquid oxygen.

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