Please explain the silver mirror reaction with silver ammonia solution, thank you.

Silver Mirror reaction. Experimental Methods.

Add 1ml of 2% silver nitrate solution to a clean test tube, and then drip 2% dilute ammonia drop by drop while shaking the test tube, only the initial precipitate is just dissolved (this is the resulting solution called silver ammonia solution).Add another 3 drops of acetaldehyde, shake and warm the tube in hot water. Soon you can see that a layer of metallic silver is attached to the inner wall of the test tube, which is as bright as a mirror.

Reaction essence. In this reaction, the silver ammonia solution produced by silver nitrate and ammonia contains silver ammonia hydroxide, which is a weak oxidizing agent that oxidizes acetaldehyde to acetic acid, which in turn reacts with ammonia to form ammonia acetate, and the silver ions are reduced to metallic silver.

Experimental phenomenon. The original silver adheres to the wall of the test tube, forming a silver mirror, and this reaction is called the silver mirror reaction.

Reaction equations.

ch3cho+2ag(nh3)2oh→ch3coonh4+2ag↓+3nh3+h2o

The principle is the weak oxidation of silver ammonia solution.

In this test, other reducing substances can be used instead of acetaldehyde, such as glucose.

Silver ammonia solution Chemical formula: AG(NH3)2OH

Configuration method. 1.Prepare the tube: Inject a small amount of NaOH solution into the tube, shake, and then heat and boil. Pour off the NAOH and wash it with distilled water for later use.

2.Prepare the solution: In a washed tube, inject 1 ml of Agno3 solution, then add ammonia drop by drop, shaking while dropping until the initially generated precipitate is just dissolved.

Silver Mirror reaction. Add three drops of acetaldehyde dilute solution along the wall of the test tube, place the tube in a beaker with hot water, and let it sit for a few minutes. Soon, a layer of mirror-like metallic silver could be observed attached to the inner wall of the test tube.

Notes:1One of the keys to the success or failure of the silver mirror reaction is whether the instrument used is clean.

2.When preparing a silver ammonia solution, it should be prevented from adding excessive ammonia. The silver ammonia solution must be used with the mixture and cannot be used for a long time.

3.After the experiment, the silver ammonia solution in the test tube should be treated in time, a small amount of hydrochloric acid should be added first, the mixed solution should be poured out, and then a small amount of dilute nitric acid should be used to wash off the silver mirror, and washed with water.

The silver ammonia solution produced by silver nitrate and ammonia contains silver hydroxide diaminohydroxide, which is a weak oxidizing agent that can oxidize acetaldehyde into acetic acid, which in turn reacts with the generated ammonia to form ammonium acetate, and the silver ions are reduced to metallic silver. The silver produced by reduction adheres to the wall of the test tube, forming a silver mirror.

Silver ammonia: silver ammonia hydroxide (Ag(NH3)2OH) silver mirror reaction: CH

cho+ag(nh

oh (water bath) ch

coonhag↓+

nhho

Silver Mirror reaction. Principle: Silver ammonia solution has weak oxidizing properties.

Phenomenon: Add 1ml of 2% silver nitrate solution to a clean test tube, then add 2 drops of 10% sodium hydroxide aqueous solution, shake the test tube, and you can see the white precipitate. Then drop 2% dilute ammonia dropwise until the initial precipitate is dissolved (the resulting solution is called silver ammonia solution).

Finally, 3 drops of acetaldehyde are added, and the test tube is warmed in hot water after shaking. Soon it will be seen that a layer of bright metallic silver is attached to the heated area of the inner wall of the test tank.

Silver mirror reaction is a chemical reaction in which the solution of silver (AG) compound is reduced to metallic silver, and the resulting metallic silver is attached to the inner wall of the container, which is as bright as a mirror, so it is called silver mirror reaction.

A common silver mirror reaction is the reduction of silver ammonia complexes (ammonia-silver complexes, also known as Toren reagents) to silver by aldehyde compounds, and the oxidation of aldehydes to the corresponding carboxylic acid ions, but in addition, some silver compounds (such as silver nitrate) can also be reduced by reducing agents (such as hydrazine) to produce silver mirrors.

Silver ammonia solution undergoes a silver mirror reaction:ch3cho+2[ag(nh3)2]oh==ch3coonh4+2ag↓+3nh3+h2o。

1. Preparation of silver ammonia solution stuffy:

nh3·h2o + agno3 ==agoh + nh4no3 ；AgoH + NH3·H2O ==AG(NH3)2OH + H2O (Operation: Add ammonia dropwise to the silver nitrate solution until the initial precipitate happens to be completely dissolved!) ）

Second, the silver mirror reaction:

The silver mirror reaction is a chemical reaction in which the solution of silver compounds is reduced to metallic silver, and it is called the silver mirror reaction because the metallic silver produced is attached to the inner wall of the container and is as bright as a mirror. A common silver mirror reaction is a reaction in which the silver ammonia complex is reduced to silver by aldehyde compounds, and the aldehyde is oxidized to the corresponding carboxylate ions.

3. Reaction conditions:

1. The reaction is under alkaline conditions, which needs to be heated in a water bath; Formaldehyde, acetaldehyde, acetaldehyde and other aldehydes contain aldehyde groups (such as various aldehydes, as well as a certain ester of formate, etc.) (glyoxal requires 4mol silver ammonia solution because there are two aldehyde groups);

2. Formic acid and its salts, such as HCOOH, HCOONA, etc.; Formate, such as ethyl formate HCOOC2H5, propyl formate HCOOC3H7, etc.; Sugars containing aldehyde groups in molecules such as glucose and maltose.

Fourth, the application:

1. The silver mirror reaction is a qualitative repentant slip experiment used to test aldehydes and reducing sugars, mainly used to detect the existence of aldehyde groups (i.e., -cho). This experiment is simple to operate, the phenomenon is obvious, and it is easy to observe. This reaction is used in the laboratory to identify compounds containing aldehyde groups.

2. In industry, this reaction is used to coat glass with silver mirrors and thermos flasks. This experiment is mainly used in the mirror industry, and is also used for the concentration identification of organic raw materials in the industrial laboratory.

Preparation of silver ammonia solution: NH3·H2O + AGNO3 ==AGoh + NH4NO3, AGoh + NH3·H2O ==AG(NH3)2OH + H2O

Operation: Add ammonia dropwise to the silver nitrate solution until the initial precipitate happens to be completely dissolved!

Acetaldehyde silver mirror early reaction: CH3CHhe + AG(NH3)2OH = water bath heating = NH4COOH + H2O + AG +3NH3

Acetaldehyde (CH3CHO) reacts with silver ammonia solution (Tollens reagent) in silver mirror, which is a commonly used experimental method in organic chemistry. The specific reaction process is as follows:

Silver ions (Ag+) are reduced to colorless Ag(NH3)2+ ions by ammonia water (NH3).

Under alkaline conditions, acetaldehyde is oxidized to carboxylic acids, and at the same time, Ag(NH3)2+ ions are reduced, and Shengkai is formed into a reddish-brown AG precipitate, which precipitates at the bottom of the test tube to form a silver mirror.

The reaction equation is:

2ag(nh3)2+ +2oh- +ch3cho → 2ag + ch3coo- +4nh3 + 2h2o

In the experiment, we added Tollens' reagent to the acetaldehyde solution to be detected, heated the reaction, and observed whether a silver mirror was formed. If a silver mirror is generated, acetaldehyde is present in the sample. This method can be used to detect low-molecular-weight aldehydes such as formaldehyde and acetaldehyde in food, and can also be used to detect ascending nuclear reducing substances such as glucose in urine.

It is known that the chemical formula of silver ammonia solution is: Ag(NH3)2OH After the reaction, there is a black precipitate at the bottom of the test tube C, and the upper supernatant and the bottom black solid are separated for later use (1) Formic acid (HCOOH) is decomposed into CO and H2O when it encounters concentrated sulfuric acid, and the reaction reflects the dehydration of concentrated sulfuric acid (2) The function of the hose in device A is to balance the pressure up and down the funnel, so that the formic acid solution can be dropped smoothly (3) Duan is used to verify the composition of the product in the upper supernatant in C, and the following experiments are carried out:

a The pH of the supernatant was measured to be 10 b A few drops of Ba(OH)2 solution were added to the supernatant, and white turbidity was found, and a gas that could be used to turn the wet red litmus paper blue was produced c A few drops of Ba(Oh)2 solution were added to the newly prepared silver ammonia solution, and there was no obvious phenomenon The purpose of experiment C was to compare the test and exclude the interference of silver ammonia solution on the product inspection According to the above experimental phenomena, the product composition in the upper supernatant was (NH4)2CO3 (chemical formula).

1.Silver hydroxide hydroxide will generate AG3N for a long time, and the equation is:

3ag(nh3)2oh+2h2o==ag3n↓+5nh3·h2o

2.The silver ions of diaaminomy will be weakly ionized, releasing silver ions:

ag(nh3)2+==ag++2nh3

Silver diamine hydroxide [chemical formula: Ag(NH3)2OH]The essence of silver diaaminohydrate is actually silver hydroxide, Ag(NH3)2OH] is actually AgoH·2NH3, and the following components are present in the solution of silver hydroxide diaaminomy: [AG(NH3)] + ions, NH3 molecules, NH3·H2O molecules, NH4+ ions, OH- ions and very small amounts of H+ and AG+ ions.

Silver diamine hydroxide is a complex with weak oxidizing properties. It is a strong alkali, corrosive, has the universality of alkali, dissolves in water and ethanol, and can be completely ionized.