"Nitrogen and Its Compounds" Important non-metallic elements in chemical production PPT (Lesson 2: Ammonia and ammonium salts)

"Nitrogen and Its Compounds" Important non-metallic elements in chemical production PPT (Lesson 2: Ammonia and ammonium salts)

Part 1: Essential knowledge and foundation of literacy

1. Ammonia

1.Physical properties

【Situation·Thinking】

The refrigerant is liquid and can change into a gaseous state at a certain temperature. That is, it can evaporate in the evaporator of the refrigeration system and absorb heat from the object being cooled to vaporize, and then transfer the heat to the surrounding medium (water) in the condenser. or air) and become a liquid. There are many types of refrigerants. Commonly used refrigerants in air conditioners include ammonia, Freon, etc. Ammonia is currently the most widely used medium-pressure and medium-temperature refrigerant.

As a refrigerant, what properties of ammonia are used? Try to analyze its shortcomings?

Tip: Ammonia gas easily liquefies into liquid, and liquid ammonia will absorb a lot of heat when it changes into gas. The disadvantages are that it has a pungent smell, is toxic, can burn and explode.

2. Chemical properties

(1) Experimental research:

【Micro thinking】

If NH3 is replaced by NO2, can a fountain be formed? If it can be formed, can the liquid fill the flask after the experiment?

Tip: Can form a fountain, but cannot fill a flask. NO2 is easily soluble in water and reacts with water: 3NO2+H2O====2HNO3+NO, NO gas is produced, so when doing fountain experiments with NO2 and H2O, the liquid can only fill 2/3 of the volume of the flask.

【Situation·Thinking】

Plumbers use concentrated ammonia to check whether the chlorine pipeline is leaking. If there is a leak somewhere in the pipeline, white smoke will be produced. What is the principle? (It is known that 2NH3+3Cl2====N2+6HCl) Ammonia will also produce when it meets concentrated sulfuric acid. White smoke?

Tip: If the chlorine pipeline leaks, reactions will occur: 2NH3+3Cl2====N2+6HCl, NH3+HCl====NH4Cl, and the white smoke produced is solid NH4Cl; non-volatile acids such as H2SO4 and H3PO4 cannot be formed Steam will not produce white smoke when encountering ammonia.

2. Ammonium salt

1.Use and physical properties

(1) Usage: Commonly used as chemical fertilizers in agriculture, such as ammonium sulfate, ammonium bicarbonate, ammonium nitrate, etc.

(2)Physical properties:

2. Chemical properties

(1) Chemical properties of ammonium salts

[Error-prone reminder] Not all ammonium salts produce ammonia gas when decomposed by heat, such as ammonium nitrate.

(2) Experimental research

【Situation·Thinking】

A farmer uncle saw that a bag of ammonium bicarbonate fertilizer he bought was damp, so he put it in the sun to dry. When he picked it up in the afternoon, he found that it was much less. Please explain the relevant reasons?

Tip: Under the irradiation of sunlight, ammonium bicarbonate is thermally decomposed to generate NH3, CO2, and water vapor, so the solids are reduced.

3. Laboratory preparation method of ammonia gas

【Smart Judgment】

(1) Add dilute NaOH solution to a certain solution, and the wet red litmus paper does not change blue, then there must be no ____ in the original solution. ()

Tip:×. When dilute NaOH solution is added to a certain solution, even if NH3·H2O is generated, ammonia gas will not be released without heating.

(2) NH4Cl decomposes when heated, so NH4Cl and NaCl can be separated by heating. ()

Tips:√. NH4Cl decomposes when heated to form NH3 and HCl, which break away from the solid. When they reach a low temperature location, they react to form NH4Cl, thereby achieving the purpose of separating NH4Cl and NaCl.

(3) Soda lime can be used to dry ammonia in the ammonia preparation experiment. ()

Tips:√. Ammonia gas is alkaline when dissolved in aqueous solution and does not react with soda lime, so soda lime can be used to dry ammonia gas.

Nitrogen and its compounds PPT, part 2 content: key abilities and literacy formation

Knowledge Point 1: Fountain Experiment

[Key points to clarify doubts]

1.Principle and device

(1) Ammonia fountain experiment

Formation principle

When the gas comes into contact with external water or solution, the gas dissolves in large amounts or chemically reacts with the solute in the solution, resulting in a rapid decrease in the air pressure in the container. Under the action of external atmospheric pressure, the external liquid quickly enters the container and is ejected through the pointed nozzle tube. , forming a fountain.

trigger action

Open the water stop clamp, squeeze the rubber tip of the dropper, or other operations that create a pressure difference that causes the liquid to flow and spray into the container.

(2) The key to a successful experiment—“Three Essentials”

①The air tightness of the device should be good.

②Flask and gas--be dry.

③The ammonia gas in the flask should be full.

【Think·Discussion】

Fountain refers to spring water that is ejected from the ground to the ground. It is a combination of water or other liquids with a specific shape that is sprayed through a nozzle under a certain pressure. A classmate assembled a fountain experimental device (as shown in the picture).

(1) How to trigger the fountain experiment?

Tip: Open the water stop clamp and heat the flask with your hands (or hot towel, etc.). The ammonia gas will expand when heated, causing the ammonia gas to contact the water through the conduit, which will produce a fountain. (Or use a towel soaked in ice water to "cold compress" the flask so that the water enters the flask and the ammonia gas in the flask dissolves in the water)

(2) When a student was doing the fountain experiment in the textbook, he opened the water stop clamp and squeezed the water from the rubber dropper into the flask, but no fountain was produced. What are the possible reasons for the experimental error?

Tips: ① The air tightness of the device is not good; ② The purity of the collected NH3 is low; ③ The flask is not dry, etc.

【Case Demonstration】

[Typical example] (2019 Yueyang High School First Test) Substance A is a white crystal. It is heated with a concentrated NaOH solution to release colorless gas B. Use a round-bottomed flask to collect the dry gas B.

Install the instrument as shown in the figure, open the water stop clamp, and squeeze the rubber tip of the dropper to get a blue fountain. Add dilute nitric acid to the solution that releases gas B to acidify it, and then add silver nitrate solution to produce a white precipitate.

(1)The chemical formula of A is ____________.

(2) The desiccant that can be used to remove moisture from B is ________. The method of collecting gas B is _____________.

(3) The reason why the solution appears blue is ____________ (expressed in chemical terms).

(4) Take the solution in the flask after the experiment and heat it. The observed phenomenon is ____________________.

[Problem-solving guide] To answer this question, you need to pay attention to the following three points:

(1) The solubility of common gases and the acidity and alkalinity of their aqueous solutions.

(2) The principle of forming a fountain and the operation of initiating the fountain.

(3) Master the alkalinity and instability of ammonia.

Knowledge point 2: Laboratory preparation method of ammonia and testing of

[Key points to clarify doubts]

1. Laboratory preparation method of ammonia gas

(1) Reaction principle:

2NH4Cl+Ca(OH)2 2NH3↑+CaCl2+2H2O

(2)Device:

(3) Selection of equipment for each part of the ammonia gas preparation experiment:

2. Other preparation methods of ammonia

3. NH4 testing method

(1)Principle:

(2)Method:

[Error-prone reminder] (1) The test tubes and conduits of the collection device and reaction device must be dry.

(2) The test tube opening of the generating device is slightly inclined downward.

(3) Since the density of ammonia is smaller than that of air, when collecting ammonia, the conduit port should be inserted into the bottom of the test tube.

(4) The cotton ball is dipped in dilute sulfuric acid to prevent air convection and ammonia gas from escaping and polluting the air.

(5) P2O5, concentrated sulfuric acid and other acidic desiccants cannot be used to dry NH3, nor can CaCl2 be used for drying. The reason is that CaCl2 reacts with NH3 to form CaCl2·8NH3.

【Think·Discussion】

(1) When preparing ammonia in the laboratory, NaOH and KOH are not used as bases. What is the reason?

Tip: Slaked lime cannot be replaced by NaOH and KOH. The reason is that NaOH and KOH are hygroscopic and easy to agglomerate, which is not conducive to the production of ammonia gas and will corrode the test tube under heating conditions.

(2) Based on the thermal decomposition properties of ammonium salts, a classmate thinks that heating NH4Cl can be used to prepare ammonia gas. What do you think?

Tip: No. NH4Cl decomposes to obtain NH3 and HCl. The two gases react when cold at the mouth of the test tube to form NH4Cl, and ammonia is not obtained.

【Case Demonstration】

[Typical example] A learning interest group explored the experiment of producing ammonia:

(1) Student A plans to use the following experimental methods to prepare ammonia gas, of which the reasonable one is ____.

A. Decompose ammonium chloride solid by heating

B. Drop concentrated ammonia water into the solid sodium hydroxide

C. Add solid sodium hydroxide to concentrated ammonia water

D. Drop the dilute ammonium chloride solution into the solid sodium hydroxide

(2) Based on the above correct principles, the student wants to use the following common laboratory gas production equipment to produce ammonia gas. The suitable equipment is ________.

(3) The properties of gas are the main basis for the selection of gas collection methods. The following properties have nothing to do with the collection method: __________.

① Density ② Color ③ Solubility ④ Thermal stability ⑤ Reaction with oxygen

(4) The picture below shows several devices designed by student A to collect ammonia gas. Among them, the feasible one is ____________, and the principle of gas collection is ____________.

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