"Integration and Improvement at the End of Chapter" Elements and Material World PPT

"Integration and Improvement at the End of Chapter" Elements and Material World PPT

Part One: 1. Classification methods and their application in life

1. Classification of elements and substances

(1) Elements exist in nature in free and combined states, and very active elements can only exist in combined states. Elements such as sodium and chlorine are not free in nature.

(2) Different angles of substance classification lead to different classification results.

(3) Compounds can be divided into electrolytes and non-electrolytes.

(4) Chemical reactions can be divided into redox reactions and non-redox reactions, and the distinction is based on whether there is electron transfer.

(5) The mutual transformation relationship diagram between elements, oxides, acids, bases and salts is a powerful tool for learning chemistry.

2. Application of classification methods

(1) Use classification methods to judge or predict the properties of substances

For example, zinc and iron are both metal elements. It is known that they can react with certain non-metallic elements, acids, salts, etc. It is also known that aluminum is also a metal element, so aluminum should also have the general properties of zinc, iron and other metal elements.

(2) Use classification methods to find substances with the same or similar properties

For example, hydrochloric acid (HCl) and sulfuric acid (H2SO4) are both acids and have acid properties.

(3) Use classification methods to identify substances

For example, when choosing chemical reagents to identify six solutions such as dilute sulfuric acid, dilute hydrochloric acid, NaOH, BaCl2, KNO3, and Ca(OH)2, you can first use litmus solution to divide them into three categories according to the difference in acidity and alkalinity, and then group them. identification.

① Dilute sulfuric acid and dilute hydrochloric acid can make litmus solution red (acidic).

② What can make litmus solution blue (alkaline) is NaOH solution and Ca(OH)2 solution.

③The ones with no obvious phenomenon (neutral) when encountering litmus solution are BaCl2 solution and KNO3 solution.

[For training]

1. (2019•Yichang Gezhouba Middle School Senior High School Examination) The correct classification or classification of the following related substances is ()

① Liquid chlorine, dry ice, and magnetic iron oxide are compounds; ② Hydrochloric acid, Bordeaux mixture, and aqua regia are mixtures; ③ Alum, soda ash, and caustic soda are electrolytes; ④ Milk, soy milk, and iodine are colloids; ⑤ Baking soda, soda ash, and caustic soda are sodium salts

A． ①② B． ②③

C. ③④ D. ②③⑤

2. A chemical interest group wants to study the properties of H2SO4, BaCl2, Na2CO3, NaCl, and NaOH. They have designed two research plans on how to study:

Plan Ⅰ: Classify them according to acid, alkali, and salt, and then dissolve them in water to obtain solutions, and conduct experiments;

Scheme II: Classify them according to sodium salts and other compounds, then dissolve them in water to obtain solutions, and conduct experiments.

(1) When classifying according to Scheme I, a student found that Na2CO3 solution was also alkaline, so he classified both Na2CO3 and NaOH as alkalis. Is it reasonable? Please explain why.

__________________________________________________.

(2) Please write down the ionic equation for any reaction between the two groups of substances in Scheme II:

__________________________________________________.

(3) A student in this interest group believes that the above five substances can also be divided into two categories: Na2CO3, NaCl, NaOH, H2SO4, and BaCl2 based on whether they contain sodium. When using H2SO4 to identify three sodium-containing substances, Na2CO3 is easily distinguished, but it is difficult to identify NaCl and NaOH. Can you help solve this problem?

Integrate and improve PPT at the end of the chapter, part 2: 2. Judgment method of electrolytes and non-electrolytes - "Three Looks"

1. A look at the material categories

First, classify the given substances into categories such as elements, mixtures, and compounds.

2. Second, look at the types of compounds

Classify compounds into acids, bases, salts, oxides, and other categories.

3. Third look at special substances

Before classifying, first clarify that acids, alkalis, and salts are electrolytes, and then check whether there are metal oxides in the remaining substances. Most metal oxides are electrolytes, and the remaining compounds are generally non-electrolytes.

[For training]

3. Among the following four groups of substances, the former is an electrolyte and the latter is a non-electrolyte ()

A． Carbon dioxide Sodium carbonate B. Sodium sulfate ethanol

C. Aluminum oxide sulfur D． Sucrose Sodium hydroxide

4. Which of the following groups is completely correct regarding the classification of strong electrolytes, weak electrolytes, and non-electrolytes ()

Options A B C D

Strong electrolyte Fe NaCl CaCO3 HNO3

Weak electrolyte CH3COOH NH3 H3PO4 Fe(OH)3

Non-electrolyte C12H22O11 BaSO4 C2H5OH H2O

Integrate and improve PPT at the end of the chapter, the third part: 3. Judgment of correctness and incorrectness of ionic equations and coexistence of ions

1. Determining whether the ionic equation is correct or incorrect

(1) Check whether the ion reaction conforms to objective facts

For example: reaction of iron with dilute hydrochloric acid

2Fe＋6H＋===2Fe3＋＋3H2↑(error);

Fe＋2H＋===Fe2＋＋H2↑(correct).

(2) See whether the ion reaction obeys the law of conservation of mass

For example: sodium reacts with water

Na＋H2O===Na＋＋OH－＋H2↑(error);

2Na＋2H2O===2Na＋＋2OH－＋H2↑(correct).

(3) See whether the ionic reaction obeys charge conservation

For example: reaction between copper and silver nitrate solution

Cu＋Ag＋===Cu2＋＋Ag(error);

Cu＋2Ag＋===Cu2＋＋2Ag (correct).

(4) Check whether the reactants and products are separated correctly

For example: reaction of NaHCO3 solution and dilute hydrochloric acid

CO2-3+2H+===CO2↑+H2O(error);

HCO-3+H+===CO2↑+H2O (correct).

(5) Check whether ion reactions are missed

For example: reaction between copper sulfate solution and barium hydroxide solution

Ba2++SO2-4===BaSO4↓(error);

Ba2＋＋2OH－＋Cu2＋＋SO2－4===BaSO4↓＋Cu(OH)2↓(correct).

(6) Check whether the composition principle is followed (i.e. the ratio of anions and cations)

For example: reaction of Ba(OH)2 solution and dilute sulfuric acid

Ba2＋＋OH－＋H＋＋SO2－4===BaSO4↓＋H2O(error);

Ba2＋＋2OH－＋2H＋＋SO2－4===BaSO4↓＋2H2O (correct).

2. Ion coexistence

(1) Slightly soluble substances or precipitates are generated and cannot coexist in large amounts, such as OH- and Mg2+,

Fe3+, Al3+, Cu2+, Fe2+, Ca2+, Ba2+ and SO2-4, CO2-3, Cl- and Ag+, etc.

(2) The generated gases escape and cannot coexist in large amounts, such as H+ and CO2-3, HCO-3, S2-, HS-, NH+4 and OH-, etc.

(3) Weak electrolytes are generated and cannot coexist in large amounts, such as H+ and CH3COO-, OH-, ClO-, etc.

(4) Colored ions cannot exist in the "colorless solution", such as Fe3+ (brown), Fe2+ (light green), MnO-4 (purple), Cu2+ (blue), etc.

Integrate and improve PPT at the end of the chapter, part 4 content: 4. Oxidation-reduction reaction

1. The relationship between the basic concepts of redox reactions

Among them, reducing properties: reducing agent > reduction products; oxidizing properties: oxidizing agent > oxidation products.

2. Principle and Application of Conservation of Gained and Lost Electrons

(1) Conservation of electrons gained and lost: The total number of electrons gained by the oxidizing agent is equal to the total number of electrons lost by the reducing agent.

(2) Use the principle of conservation of gained and lost electrons to solve related calculation problems - first "find" and then "list".

By using conservation thinking, you can put aside the tedious reaction process and do not have to write out the chemical equation of the reaction, thus solving related problems faster and more conveniently. The calculation steps are as follows.

① "Find": First find out the amount of oxidizing agent, reducing agent and their substances, as well as the amount of substances that gain and lose electrons per mole of oxidizing agent and reducing agent.

② "Column": From the amount of the substance in the question, according to the conservation of electrons gained and lost, the equation is listed:

[For training]

7． Sodium hydride (NaH) is a hydrogen generating agent that can react NaH+H2O===NaOH+H2↑. The correct description of this reaction is ()

A． NaH is an oxidizing agent

B． Generate 1 mol H2 and transfer 2 mol electrons

C. NaOH is the reduction product

D. The mass ratio of oxidation products to reduction products is 1:1

8. (2019·Jining Peiwen School High School Grade 1) It is known that 30 mL of Na2SO3 solution with a concentration of 0.5 mol·L-1 reacts completely with 50 mL of KRO4 solution with a concentration of 0.1 mol·L-1 and is converted into Na2SO4. Then the valence of R element in the product is ()

A． +1 price B． +2 price

C. +3 price D． +4 price

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