"Several Common Bases" Acids and Bases PPT Courseware 4

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"Several Common Bases" Acids and Bases PPT Courseware 4

Knowledge review

Knowledge point 1: Physical properties of sodium hydroxide and calcium hydroxide

Sodium hydroxide: white solid, ____ dissolves in water and releases a lot of heat. Easily absorbs moisture and is highly corrosive.

Calcium hydroxide: white powdery solid, __soluble in water, corrosive.

[ Note Also keep it sealed.

② Calcium hydroxide can be produced by reacting quicklime with water. This reaction can release a large amount of heat. The reaction equation is:

CaO＋H2O==____________

Knowledge point 3: The concept and essence of neutralization reaction

The reaction in which an acid and a base produce ___ and ___ is called a neutralization reaction. The essence of the reaction is that the H+ dissociated from the acid reacts with the OH- dissociated from the base to form water: H++OH-==H2O.

[Attention]

① Many neutralization reactions do not have obvious experimental phenomena (such as the reaction between NaOH solution and dilute hydrochloric acid), and indicators are often needed to judge the occurrence of the reaction. For example, adding phenolphthalein solution to an alkaline solution turns the solution red. During the dropwise addition of acid, when the red color of the solution just turns colorless, it means that the acid and base have reacted completely.

② When the neutralization reaction occurs, heat will be released.

Example analysis

►Type 1: Changes in air exposure to acid and alkali solutions

Propositional perspective: Properties of concentrated acids and bases.

Example 1 The mass of the following substances will be reduced if they are exposed to the environment ()

A. Sodium hydroxide B. Concentrated sulfuric acid

C. Concentrated hydrochloric acid D. calcium carbonate

[Method Instructions] Some of the mass changes of acid and alkali solutions exposed to air are physical changes, and some are chemical changes. The change in mass caused by physical changes is the decrease in mass caused by the volatilization of the substance itself or the increase in mass due to the absorption of moisture in the air. Chemical change is when a substance absorbs components such as oxygen, carbon dioxide or water in the air at room temperature, causing deterioration or an increase in quality.

[ Analysis The mass will be reduced if the mouth is placed in the air.

►Type 2: Chemical properties of acid and alkali solutions

Proposition angle: Explore the chemical properties of acids and bases.

Example 2 The experimental team studied the chemical properties of hydrochloric acid and calcium hydroxide and conducted 8 experiments as shown in the figure.

Known: Na2CO3＋CaCl2===CaCO3↓＋2NaCl

(1) After the experiment, there was a yellow solution in a certain test tube. The chemical equation of the reaction in the test tube ____________________.

(2) After the experiment, there was a red solution in a test tube. Add enough ______ to it and the solution became colorless. It can be inferred that the substance originally contained in the test tube was __________.

(3) After the experiment, there was a white solid at the bottom of a test tube. After filtering, dilute hydrochloric acid was added dropwise to the filtrate. After a period of time, bubbles appeared. It can be inferred from this that the

The chemical equation for the initial reaction in the test tube is _______________.

(4) After the experiment, only a colorless solution was obtained in a certain test tube. A sufficient amount of Na2CO3 solution was added to it, and there was no obvious phenomenon. It can be inferred that the chemical equation for the initial reaction in the test tube is ____________, and the solute in the original colorless solution is ____________ (write all possibilities).

►Type 3: Experimental design for the reaction of NaOH solution and CO2

Propositional perspective: Analysis of the reaction phenomena and products of NaOH solution and CO2.

Example 3: A classmate of an interest group passed CO2 into clear lime water and sodium hydroxide solution respectively, and observed that the former became turbid, but the latter had no obvious phenomenon.

(1)Write the chemical equation for the above clear limewater to become turbid_____________________.

(2) In order to explore whether there is a chemical reaction between CO2 and NaOH, Wang Qiang designed experiments A and B as shown in the figure to verify that there is a chemical reaction between CO2 and NaOH solution. Experimental phenomenon: The liquid level in the test tube in A rises; the balloon in B expands.

①Wang Qiang believes that the above experiment is feasible, and its common principle is ____________________.

② Li Li questioned. She believed that the above experiment was not rigorous. The reason was ____________________. To obtain scientific and rigorous conclusions, the device should still be used and the additional controlled experiment is _______________.

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Update Time: 2024-11-16

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