membershipSalt and fertilizers
Cheats. 1.In the middle school entrance examination, the properties and uses of common salts are examined in the form of experiments, and the presence of ions in them is tested; In the process of solving the problem, the relevant chemical equations are combined to solve the problem. The question types mainly include multiple-choice questions, inference questions and ** questions, etc., which are mainly combined with the actual examination of production and life, which is more difficult and is also a hot spot in the high school entrance examination;
2.The conditions for the occurrence of the complex decomposition reaction and the writing, coexistence problems and impurities removal methods of the chemical equation are the hot spots of the middle school entrance examination, and the examination forms are diverse, often combined with other knowledge, and the comprehensive is strong. When reviewing, students should be proficient in basic knowledge such as solubility formulas and the conditions under which metathesis reactions occur, and use comparative methods to build a knowledge network for effective review.
3.The high school entrance examination will examine the effects of nitrogen, phosphorus and potassium on plant growth and their deficiencies, the characteristics of common chemical fertilizers and ammonium nitrogen fertilizers, and the judgment ability and knowledge transfer ability of compound fertilizers. This part of the content is often used as multiple-choice questions in the high school entrance examination. Fill-in-the-blank questions appear.
4.This topic focuses on the training and practical application of chemical knowledge and chemical laboratory operation skills, focusing on the combination of learning and application, and paying more attention to the combination of daily life.
Knowledge is essential. 1. Several common salts
Concept: A class consisting of metal ionsor ammonium ionsand acid ions.
Common salts and their uses
[Tips].
Soda ash (Na2CO3) is not a base and belongs to salt.
Hou Debang, a famous chemist in China, has made outstanding contributions to improving the production of soda ash.
Characteristics of common salts
Second, the universality of salt
Chemical properties of salt
Metathesis reaction
1) Definition: The reaction in which two compounds exchange components with each other to generate two other compounds is called metathesis reaction.
2) Features: double exchange, price unchanged.
3) Expression: ab cd ad cb.
4) The conditions under which the reaction occurs.
At least one of the two compounds is soluble in water and must have a precipitate or gas or water formation after exchanging components with each other.
[Special Reminder].
The solubility of salts and alkalis can be judged according to the "solubility table of acids, alkalis, and salts", and the conditions of reactants and products in the metathesis reaction can be combined to determine whether the metathesis reaction can occur.
The eight major precipitates (four salts and four alkalis) that must be mastered in junior high school:
White precipitate: BaSO4, AGCL (insoluble in acid);
White precipitate: CaCO3, BaCO3, Mg(OH)2, Al(OH)3, blue precipitate: Cu(OH)2, reddish-brown precipitate: Fe(OH)3 (soluble in acid).
5) Metathesis reactions can be subdivided into the following five subtypes.
Removal of insoluble impurities in coarse saltSee Experimental Breakthrough for details
3. Chemical fertilizers
Types and functions of chemical fertilizers
[Clever Learning]."NPK, a tendon (leaf rhizome)".
Simple identification of chemical fertilizers
Inspection and precautions of ammonium nitrogen fertilizer
1) Inspection: Ammonium nitrogen fertilizer can release gases with pungent odor when encountering alkaline substances, such as ammonium chloride and hydrated lime The chemical equation of the reaction is 2NH4Cl Ca(OH)2===CaCl2 2NH3 2H2O.
2) Precautions for use: Ammonium ammonia fertilizer cannot be mixed with alkaline substances, because NH4 and OH will generate NH3, thereby reducing fertilizer efficiency.
Rational application of chemical fertilizers
Chemical fertilizers and pesticides play an important role in improving the yield of agricultural products, but they will also bring environmental problems, so it is necessary to apply fertilizers and pesticides rationally, improve application efficiency, and pay attention to reducing negative effects.