[Core test center combing].
1. The nature of nitric acid
1.Physical.
Pure nitric acid is a colorless, pungent smell liquid, low boiling point, volatile, in the air in the form of "white mist", the mass fraction of more than 95% of the concentrated nitric acid is called "fuming nitric acid".
2 Chemical properties.
1) Acidity: It is a strong acid and has the general properties of acid, such as CaCO3 reacts with Hno3 CaCO3 2Hno3 (dilute) ===Ca(NO3)2 CO2 H2O.
2) Instability: easy to decompose when exposed to light or heat, the chemical equation is 4Hno3 = 4NO2 O2 2H2O.
Commercially available concentrated HNo3 is yellow, and the No2 produced by the decomposition of nitric acid is dissolved in nitric acid, so the concentrated Hno3 should be stored in a brown reagent bottle, placed in a cold and dark place, and cannot be used with rubber stoppers.
3) Strong oxidation:
Reacts with metals:
Nitric acid is highly oxidizing and can react with most metals except gold, platinum, and titanium.
The chemical equation for the reaction of a Cu with concentrated Hno3 is Cu 4Hno3 (concentrated) ===Cu (NO3)2 2NO2 2H2O.
The chemical equation for the reaction of Cu with dilute Hno3 is 3Cu 8Hno3 (dilute) ===3Cu (NO3)2 2O 4H2O. Note: Experimental phenomena of [Experiment 5-8].
It shows both oxidation and acidity of Hno3, Hno3 No2, NO2, oxidation, Hno3 Cu(NO3)2, acidity.
B Reaction with Fe and Al: concentrated nitric acid at room temperature can form a dense oxide film on the surface of iron and aluminum and passivate, so concentrated nitric acid can be contained in iron containers or aluminum containers.
Reacts with non-metals:
The chemical equation for the reaction of carbon with concentrated nitric acid is C 4Hno3 (concentrated) = CO2 4NO2 2H2O. Only oxidation is expressed.
3 Industrial Method.
Nitric acid is an important chemical raw material, which is used to make fertilizers, pesticides, explosives, dyes, etc. The principle of industrial nitric acid production is to obtain nitric acid by passing ammonia through a series of reactions, as shown in the figure below
Second, the use of nitric acid
Nitric acid is an important chemical raw material, commonly used to make nitrogen fertilizers, explosives, fuels, plastics, nitrates, etc.
Core induction] 1 Strong oxidation of nitric acid.
The 5-valent nitrogen element in HNO3 has a strong electron-gaining ability. The greater the concentration of nitric acid, the higher the reaction temperature, and the stronger its oxidation.
1) Reaction of nitric acid with metals.
Except for a few metals such as Au and Pt, nitric acid can oxidize almost all metals, such as 3AG 4HNO3 (dilute) ===3AGno3 No 2H2O;
The reaction between active metal and nitric acid does not produce H2, and the concentration of nitric acid is different, and the reduction products are different;
At room temperature, concentrated nitric acid can passivate Fe and Al.
2) Reaction of nitric acid with non-metals.
Reaction law: non-metallic elemental concentrated nitric acid most ** oxide or its oxygenated acid NO2 H2O;
Example: C 4Hno3 (concentrated) = CO2 4NO2 2H2O.
3) Reaction of nitric acid with reducing compounds.
The strong oxidation of nitric acid is also manifested in the fact that it can oxidize reducing compounds or ions, such as Hi, HBR, SO2, Fe2, FeO, BR, I, S2, SO32-, etc., which can be oxidized by Hno3.
2 Calculation of the reaction of nitric acid with metals.
1) Conservation of electrons: The reaction between nitric acid and metal is a redox reaction, and the total number of electrons obtained by the nitrogen atom is equal to the total number of electrons lost by the metal atom.
2) Atomic conservation method: when nitric acid reacts with metal, the NO part of nitric acid still exists in the form of NO before the reaction, and part of it is converted into a reduction product, and the sum of the amount of N substances in these two parts is equal to the amount of N substances in the nitric acid consumed by the reaction.
3) Calculation by ion equation: the reaction between nitric acid and sulfuric acid mixture with metal, when the metal is sufficient, can not be calculated by the chemical equation of nitric acid and metal reaction, and the ion equation is used to calculate, because the NO in the generated nitrate and the h ionized by sulfuric acid can still continue to react with the metal. For example, the reaction equation between metal copper and mixed acid is 3Cu 8H 2NO3-===3Cu2 2No 4H2O.
Typical Example Question] Example 1 Which of the following statements about nitric acid is true.
a Nitric acid reacts with active metals to produce hydrogen and the corresponding nitrate.
b The greater the concentration of nitric acid, the stronger its oxidation.
c Dilute nitric acid dissolves Fe(OH)2 to generate Fe(NO3)2 and water.
d Aqua regia is a mixture of concentrated nitric acid and concentrated hydrochloric acid with a volume ratio of 3 1 that dissolves gold and platinum.
Example 2 The following statement is correct.
A Na2O is placed in the air for a long time and is eventually converted to NaHCO3
b. Concentrated nitric acid is decomposed by photoiculture to produce colorless and odorless mixed gas.
c Ammonium salts are easily decomposed when heated, and do not necessarily produce NH3
Sodium peroxide was added to the solution of D alcl3, and a white precipitate was finally formed.
Example 3 will be 768 g of copper reacts exactly completely with 50 ml of nitric acid at a certain concentration, collected under standard conditions448 l gas. Please answer:
1) The volume of no is l, and the volume of no2 is l.
2) The amount of nitric acid that is reduced is mol.
3) The concentration of nitric acid is mol·l 1.
2. Acid rain and prevention
1.The concept of acid rain.
The pH of normal rainwater is about 56. This is because of the dissolution of carbon dioxide in the rainwater. ph＜5.6 of the precipitation is called acid rain.
2.Formation of acid rain.
1) Sulfur dioxide, nitrogen oxides and their reaction products in the atmosphere are dissolved in rainwater to form acid rain.
2) The formation process of sulfuric acid rain.
Write out the chemical equation shown in the designation:
2so2＋o2≒2so3；
so2＋h2oh2so3；
so3＋h2o===h2so4；
2h2so3＋o2===2h2so4。
3) The formation process of nitric acid rain.
Write out the chemical equation shown in the designation:
2no＋o2===2no2；
3no2＋h2o===2hno3＋no。
Core Summary] Common environmental pollution.
Typical example] Example 1Smog seriously threatens the ecological environment in which people live. The following measures are not feasible ( ).
a.Desulfurization of coal to reduce SO2 emissions into the atmosphere
b.Industrial waste gases containing SO2 and other substances are treated harmlessly before being emitted into the atmosphere.
c.In order to increase the industrial output value, vigorously build cement factories and steelmaking plants.
d.Use clean fuels such as natural gas and methanol for vehicles such as automobiles.
Example 2Acid rain is acidic (pH less than 5.).6) A general term for precipitation. The following statement is incorrect ( ).
a SO2 in the air dissolves in water and eventually forms acid rain.
b Nitrogen oxides (NOx) are found in exhaust gases from motor vehicles and from nitric acid and fertilizer plants.
c Arbitrary discharge of industrial wastewater is the main cause of acid rain.
d In order to reduce the formation of acid rain, SO2 emissions must be reduced and fuel desulphurization must be treated.
[Core test center combing].
1. The nature of nitric acid
Typical example] Example 1
Answer] B Explained].
a nitric acid reacts with active metals to produce nitric oxide or nitrogen dioxide gas and the corresponding nitrate, a error;
b The greater the concentration of nitric acid, the stronger its oxidation, b correct;
c Dilute nitric acid can dissolve Fe(OH)2 to form Fe(NO3)3 and water, C error;
d Aqua regia is a mixture of concentrated nitric acid and concentrated hydrochloric acid with a volume ratio of 1 3, which can dissolve gold and platinum, d false;
Therefore, choose B. Example 2
Answer] C Explanation].
A Na2O is placed in the air for a long time and is eventually converted into sodium carbonate, so A is wrong;
b concentrated nitric acid light decomposes into NO2, O2, H2O, NO2 is reddish-brown gas, with a pungent odor, so B is wrong;
c Ammonium salt is unstable, easy to decompose when heated, ammonium chloride is decomposed into ammonia and HCL when heated, if the acid that makes up ammonium salt is a strong oxidizing acid, such as ammonium nitrate is decomposed by heat to produce nitric acid to oxidize ammonia, so C is correct;
d sodium peroxide reacts with water 2Na2O2+2H2O=4NaOH+O2, and then AlCl3 reacts with NaOH solution according to 1 4 to form Naalo2, no precipitation is generated, so D is wrong;
The answer is c. Example 3
Answer] (1)0448 4.032 (2)0.2 (3)8.8
2. Acid rain and prevention
Typical example] Example 1
Answer] C Explanation].
Sulfur dioxide can lead to the occurrence of acid rain, so desulfurization of coal combustion is carried out to reduce the emission of SO2 to the atmosphere, which is conducive to protecting the ecological environment, and item A is correct; Industrial waste gases such as SO2 pollute the environment, which can lead to acid rain, and nitrogen dioxide can also cause photochemical smog, so it is necessary to treat the industrial waste gas harmlessly and then discharge it into the atmosphere, item b is correct; Vigorously build cement plants and steelmaking plants, which will emit dust, waste water and polluting gases, and increase industrial output value cannot be at the cost of destroying the ecological environment. The combustion products of natural gas, methanol, etc. have little pollution to the environment, so the use of clean fuels for vehicles such as automobiles can protect the environment, and item D is correct.
Example 2 Answer C
Analysis The arbitrary discharge of industrial wastewater causes the pollution of rivers and lakes, while acid rain is caused by the dissolution of SO2 and NO2 in water.