Luo Ying
1. Which is more non-metallic, nitrogen or phosphorus, and which is more active, nitrogen or phosphorus, and how to explain it?
Answer: According to the position of nitrogen and phosphorus in the periodic table, nitrogen is more non-metallic than phosphorus.
It is easy to know the difficulty of the reaction of oxygen with nitrogen and phosphorus respectively, and the chemical properties of phosphorus are more active than that of nitrogen.
The ease with which an atom can obtain electrons can be used to explain the strength of the non-metallic nature of an element. For example, the easier it is for an atom to get electrons, the stronger the non-metallic nature of the element, and the more difficult it is for an atom to get an electron, the weaker the non-metallic nature of the element. The strength of an element's non-metallic properties is judged by the relationship between the position of the element in the periodic table and the properties of the element.
The ease with which a chemical reaction occurs is the activity of the element. For example, the reaction conditions between sodium and water at room temperature are relatively low, so the properties of sodium are more active, and the chemical reaction with high requirements for reaction conditions is more difficult, so the activity of the elemental is weaker. When judging the activity of the element, it is more intuitive to analyze and judge according to the requirements of the chemical reaction conditions and the intensity of the reaction. Judging from the perspective of chemical bonds, that is, the essence of the chemical reaction of a substance is the formation of new chemical bonds and the breaking of old chemical bonds, and there is an inseparable relationship between the activity of a substance and the chemical bonds within its molecule. The bond energy of the covalent bond in the nitrogen molecule is very large, while the bond energy of the covalent bond in the phosphorus molecule is small, so the phosphorus element is more chemically active than the nitrogen element.
2. What is the reason why ammonia is so easily soluble in water?
A: Mainly because:
(1) Ammonia molecules and water molecules are easily bonded by hydrogen bonds.
(2) NH3 and H2O are both polar molecules, and it can be seen from the principle of similar missolution that solvents composed of polar water molecules can dissolve NH3, a solute composed of polar molecules, so NH3 is easily dissolved in water. And at room temperature, under normal pressure, 1 volume of water dissolves about 700 volumes of ammonia.
3. What particles are present in ammonia?
答:氨水中共存在6种粒子， 其中有3种分子：NH3、H2O、NH3· H2O; 3种离子： NH+4、OH-、H3O+(常简写为H+)。
4. Who has strong oxidizing properties of concentrated HNO3 or dilute HNO3?
Answer: The oxidation of concentrated NHO3 is stronger than that of dilute HNO3. The strength of the oxidation of the oxidant refers to the strength of the ability of the oxidant to seize electrons in the chemical reaction, that is, the ability to oxidize other elements, not the degree to which the oxidant itself is reduced, that is, the valence state of nitrogen in the reduction product cannot be used as a criterion. In fact, the strength of the oxidizing capacity of nitric acid is determined by the amount and concentration of nitric acid - the greater the concentration of nitric acid, the stronger its oxidizing capacity. For example, dilute HNO3 can only oxidize hydroiodic acid to I2, while concentrated HNO3 can oxidize hydroiodic acid to iodic acid.
5. What is the product of the combustion of phosphorus in chlorine gas?
A: Due to
PCl3 can also react with chlorine:
Therefore, in general, the combustion of phosphorus in chlorine usually produces a mixture of PCl3 and PCl5.
6. What are the positive and negative valencies of phosphorus and chlorine in PCl3 and PCl5, and why does this happen?
Answer: In PCl3 and PCl5, both are phosphorus positive valence, chlorine is negative, the reasons are as follows: in the periodic table, phosphorus and chlorine are both in the third period, but phosphorus is in group V.A, chlorine is in group VII.A, and chlorine is more non-metallic than phosphorus. The chemical bonds in PCl3 and PCl5 molecules are all covalent bonds P—Cl, because the non-metallic phosphorus of the element is weaker than that of chlorine, and the attraction ability of the nucleus to the shared electron pair is also weaker than that of chlorine, so that the shared electron pair deviates from the phosphorus atom and biases towards the chlorine atom. Therefore, in PCl3 and PCl5, phosphorus is positive and chlorine is negative.
7. In PCl3 and PCl5 molecules, do the individual atoms reach a stable structure with the outermost electron shell of 8 electrons?
Answer: In PCl3 molecule, the phosphorus and chlorine atoms have reached a stable structure with the outermost electron shell of 8 electrons, while in the PCl5 molecule, the chlorine atom has reached a stable structure with the outermost electron shell of 8 electrons, while the phosphorus atom is not.
8. Is NO2 the anhydride of HNO3?
Answer: NO2 is not the anhydride of HNO3, N2O5 is the anhydride of HNO3, because anhydride refers to the oxide produced by the dehydration of oxygenated acid (excluding organic anhydride), its main feature is that the acid-forming elements contained in the anhydride are consistent with the valence of the acid-forming elements in the hydrate corresponding to the anhydride (i.e., oxygenated acid).
9. Why is ammonium chloride used instead of ammonium nitrate, ammonium sulfate or ammonium carbonate in ammonia production?
Answer: Ammonium chloride mixed with calcium hydroxide has a fast reaction rate. Ammonium nitrate undergoes an explosive decomposition reaction when heated. Ammonium sulfate and calcium hydroxide produce calcium sulfate, which is easy to make the reaction mixture agglomerate, so that the generated ammonia is not easy to escape. Ammonium carbonate is separated by heat to release carbon dioxide, making the prepared ammonia impure.
10. How to check that the ammonia is full?
Answer: (1) Put the moist red litmus test paper at the mouth of the test tube where the gas is collected, if the test paper turns blue, it means that the ammonia has been collected.
(2) Put a glass rod dipped in concentrated hydrochloric acid at the mouth of the test tube for gas collection, if a large amount of white smoke is produced, it means that the ammonia has been collected.
11. How to dry ammonia and absorb excess ammonia?
Answer: The prepared gas is passed through a drying tube containing soda lime or solid sodium hydroxide to obtain dry ammonia. Excess ammonia is absorbed with a sulfuric acid solution.
12. Can ammonia be produced by reacting with strong alkali without ammonium salts?
Answer: In addition to the reaction of ammonium salt with strong alkali, the methods for preparing ammonia in the laboratory are:
(1) Concentrated ammonia is decomposed by heat;
(2) Solid strong alkali mixed with concentrated ammonia, quicklime mixed with ammonium chloride;
(3) Hydrolysis reaction of urea or magnesium nitride, etc.
13. How can I tell the difference between nitrogen dioxide gas and bromine vapor?
A: Nitrogen dioxide gas and bromine vapor are both reddish-brown gases with a pungent odor, but they can exhibit different properties and phenomena in aqueous solutions. Common methods for identifying these 2 gases are:
(1) Water solubilization method: pour an appropriate amount of distilled water into the gas collection cylinders containing nitrogen dioxide gas and bromine vapor respectively, and shake the gas collection cylinders to dissolve the gas and observe the phenomenon. If a colorless solution is formed in the gas collector cylinder, the dissolved gas is nitrogen dioxide gas, and if a yellow solution is formed in the gas collector cylinder, the dissolved gas is bromine vapor.
(2) Experimental method of silver nitrate solution: two kinds of differentiated gases are respectively passed into dilute silver nitrate solution to observe the phenomenon. If there is no new phenomenon in the solution, the gas to be tested is nitrogen dioxide, and if a yellowish precipitate is formed in the solution, the gas to be tested is bromine vapor.
(3) Organic solvent method: NO2 and bromine vapor are passed into CCl4 solution, and the orange-red one is bromine vapor.
14. Whether aluminum and iron react with cold concentrated nitric acid
Answer: Aluminum and iron can react with cold concentrated nitric acid, and the reaction belongs to redox reaction, and the oxidation product is metal oxide. Such oxides have a compact structure, dense texture, thin and uniform, firmly attached to the surface of metal solids, and extremely poor permeability, so that concentrated nitric acid cannot be penetrated, preventing the further reaction between concentrated nitric acid and metal, this phenomenon is called passivation. The passivation of aluminum and iron in cold concentrated nitric acid is the result of the redox reaction between aluminum and iron and cold concentrated nitric acid. If the oxide film on the surface of aluminum and iron is scraped off, passivation will occur again under the oxidation of cold concentrated nitric acid. Aluminum and iron are also passivated in cold fuming nitric acid. It must be noted that hot concentrated nitric acid, fuming nitric acid and cold dilute nitric acid cannot passivate aluminum and iron.
