What is Microammonia? What is the nature of ammonia

For the preparation of EDTA solution, EDTA solution was indirectly prepared with ethylenediaminetetraacetic acid disodium salt, and calcium carbonate was used as the reference substance to calibrate it. Chrome black T indicator, the total hardness of water is determined with EDTA standard solution. Adjust the pH and determine the Ca hardness in water with EDTA.

Ethylenediaminetetraacetic acid disodium salt (commonly known as EDTA) is an organic coordination agent, which can form a stable 1:1 chelate with most metal ions, and the measurement relationship is simple, so it is often used as a standard solution for coordination titration.

EDTA standard solutions are typically prepared by the indirect method. The reference materials for calibrating EDTA solution were Zn, ZNO, CaCO3, Bi, Cu, MgSO4 · 7H2O, Ni, Pb and so on. The selected calibration conditions should be consistent with the measurement conditions as much as possible to avoid systematic errors.

It is even more desirable if the pure metal or compound of the element to be measured is used as the reference material. In this experiment, CACO3 was used as the reference to calibrate EDTA, and CA indicator was used as the indicator.

Water containing calcium and magnesium ions is called hard water. The determination of the total hardness of water is to determine the total content of calcium and magnesium ions in the water, which can be determined by EDTA coordination titration. During titration, interfering ions such as Fe3+ and Al3+ can be masked with triethanolamine; Heavy ions such as Cu2+, Pb2+, and Zn2+ can be masked with KCN, Na2S, or thioglycolic acid.

The hardness of water can be expressed in a variety of ways, and this experiment requires that the total amount of Ca2+ and Mg2+ contained in each liter of water (converted to the mass of CaO) be expressed in mg·l 1.

1. EDTA-2Na·2H2O dissolves slowly in water, and can be heated to dissolve or left overnight.

2. Rigid glass bottles should be used for storing EDTA solution, and it is best to store the bottle of EDTA solution for a long time, so as to avoid the interaction between EDTA and metal ions in the glass. It is better if stored in polyethylene bottles.

3. When neutralizing HCL in the reference material, phenolphthalein can not be used to replace methyl red, ammonia neutralizes hydrochloric acid, the product NH4Cl is a strong acid and weak alkali salt, which is weakly acidic, and phenolphthalein is an alkaline indicator, so phenolphthalein can not be used as an indicator, and the discoloration range of methyl red is that it can be used as an indicator.

4. In order to prevent calcium carbonate and sodium hydroxide from precipitating in alkaline solution, the calcium and magnesium content in the water sample taken for titration should not be exceeded. Otherwise, it should be diluted with distilled water. It must be titrated immediately after the addition of the buffer solution and completed within 5 min.

5. If the sample water is acidic or alkaline, it needs to be neutralized first. If the sample water contains heavy metals such as Cu2+ and Pb2+, 1 ml of 2% Na2S solution can be added to generate sulfide precipitate. If the sample water contains A13+ and Fe3+, 2ml of triethanolamine can be added to mask it.

This is an inexact statement and can only be understood as a trace amount, such as micrograms, microliters, micromoles. The discussion can continue if necessary.

NH4+ tends to absorb an OH- in water to form ammonia monohydrate NH3·H2O so it is acidic.

You can't use the price to determine the strength or weakness. It can be judged by the difference in the stability of the product before and after the reaction.

The more stable the product, the stronger its oxidation!

It has nothing to do with the reaction conditions, but only related to the products before and after the reaction, which can be explained by the electric pair, because the electric pair only talks about the potential difference between the products before and after the reaction, such as: Cu Cu2 + electric pair.

The strength cannot be judged by the price state.

Ammonia is dissolved in water to form ammonia monohydrate, ammonia monohydrate is a weak base, and hydroxide ions and ammonium ions are reversibly ionized in water.

Ammonium ions are soluble in water, and specific problems should be analyzed: according to the different anions bound to ammonium ions, different acids and alkalinity are presented. When the anion is a strong acid ion, it is acidic, and the ammonium ion is mainly hydrolyzed.

When it is acetate, the degree of hydrolysis of the two is the same, and it is neutral, when the acidity of the acid root is less than that of acetic acid, the hydrolysis of the acid root is greater than that of ammonium and the hydrolysis of the ammonium is alkaline.

First of all, NH3 is a gas that is very soluble in water (1:700, that is, 1 volume of water can dissolve 700 volumes of NH3), NH3 is alkaline after being dissolved in water, and is called ammonia or ammonia monohydrate (chemical formula:

There is also a common gas that is very soluble in water: HCL (1:500 that is, 1 volume of water can dissolve 500 volumes of HCl) is acidic after being dissolved in water, which is called hydrochloric acid.

The difference between NH3 and HCl when dissolved in water is that ammonia is a weak alkali solution, while hydrochloric acid is a strong acid solution.

Alkaline. Because NH3+H2O<==NH3·H2O<==NH4+ +OH-

Hydroxide ions are generated, so they are alkaline.

n is -3 valence, which can be raised, generating n2 and so on.

Because of his chemical nature.

The nitrogen element in NH3 is the lowest price state of N and is easily oxidized.

So, NH3 is reductive!

n from -3 to +5.

Since ammonia acetate is a weak acid and alkaline salt, it is necessary to know its acidity and alkalinity, it depends on the acetate and ammonium ions whose hydrolysis ability is strong, if the acetate hydrolysis ability is strong, the hydroxide produced by hydrolysis will be more than hydrogen ions, it will be alkaline, and vice versa. After checking the table, it is known that acetic acid has strong hydrolysis ability, so it is alkaline.

Answer: Since the degree of hydrolysis of acetate and ammonium ions is not much different, the pH of the solution is about 7, which is neutral.

Neutral because the ionization of acetic acid and ammonia water are the same, and the degree of hydrolysis of acetate and ammonium ions is the same.

One grabs the hydrogen ions in the water, and the other grabs the hydroxide The hydrogen ions in the water have the same concentration of hydroxides, so they are neutral.

【Chemical Properties】Aqueous solution is neutral (this property is very important); Prone to deliquescent; Ammonia gas is decomposed in case of strong alkali.

It is ammonium acetate.

The ionization of ammonia and acetic acid are equal under the same conditions, so the pH of the aqueous solution of ammonia acetate should be close to 7Neutral.

Since the degree of hydrolysis of acetate and ammonium ions is basically the same, the solution is neutral.

The aqueous solution is neutral, weak acid, weak alkali salt.