"Amount of Dissolved Substance" Solution PPT Courseware 4

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"Amount of Dissolved Substance" Solution PPT Courseware 4

Preview of new knowledge

1. Solubility and Solubility of Solid Substances

1. solubility

(1) Concept: The ability of one substance to dissolve in another substance.

(2) Factors affecting the solubility of substances

①Internal cause: the nature of ____________.

②External factors: temperature.

2. solubility

Concept: Under a certain ______, the ______ dissolved when a solid substance reaches the _______ state in ______g solvent is called the solubility of this substance in this solvent.

Meaning: If the solubility of NaCl is 36 g at 20°C, it means ____________________________________.

2. Solubility curve

1. Meaning: A curve reflecting the change of solubility with _______.

2. The meaning of solubility curve

(1) Point: Indicates the solubility of the substance at a certain temperature. The intersection point indicates that the solubility of the corresponding substance at the temperature is equal.

(2) Line: Indicates the changing trend of the solubility of a substance with temperature.

(3) Surface: The one above the curve corresponds to the saturated solution of the substance at the temperature, and there is residual solid; the one below the curve corresponds to the unsaturated solution of the substance at the temperature.

[Tips] The solubility of most solid substances increases with temperature, such as______; the solubility of a few solid substances is not greatly affected by temperature, such as______; the solubility of very few solid substances increases with temperature Increase and decrease, such as ____________.

3. Gas solubility

The solubility of a gas is usually expressed by ______, that is, the solubility of a gas refers to the ________ when a gas is dissolved in a ____ volume of solvent at a pressure of 101.3 kPa and a certain temperature to reach the _______ state.

[Note] The solubility of gas is affected by pressure and temperature. As the pressure increases, the solubility of the gas ______; as the pressure decreases, the solubility of the gas ______. As the temperature increases, the solubility of the gas _____; as the temperature decreases, the solubility of the gas ________.

Interactive exploration

Research point 1: Solubility of solid substances

[Question Exploration]How to correctly understand solubility? What are the factors that affect its size?

[Inductive improvement]The concept of solid solubility includes four elements: (1) Condition: "certain temperature" must be specified. Because the solubility of solid substances changes with temperature. (2) Standard: In "100 g solvent". The amount of solvent is fixed and cannot be changed arbitrarily. (3) State: should be "saturated state". Only when the amount of solute dissolved in 100 g of solvent reaches saturation at a certain temperature is the solubility of this substance in this solvent. (4)The mass of the solute.

[Application Example]

Example 1: At 50°C, 25 g of ammonium chloride is dissolved in 50 g of water, forming a saturated solution. The correct statement about the solubility of ammonium chloride in water is ()

A． The solubility of ammonium chloride is 25 g

B． At 50°C, the solubility of ammonium chloride is 25 g

C. The solubility of ammonium chloride is 50 g

D． At 50°C, the solubility of ammonium chloride is 50 g

[Method Instructions] To correctly understand the concept of solubility, you need to grasp several key words in the concept such as "certain temperature", "100 g of solvent", "saturated state", and "mass of solute", and the problem will be easily solved.

Example 2 Figure 7-2-3 shows the solubility curves of two solid substances A and B.

(1) At t1℃, the solubility of two solid substances A and B ________ (fill in “equal” or “unequal”).

(2) To change the unsaturated solution of substance A into a saturated solution, the following relevant statement is correct ________ (fill in the letter number).

A． The mass of the solvent must become smaller

B． The mass of the solute must remain unchanged

C. The mass of the solution may not change

D． This saturated solution can also dissolve other substances

[Analysis] (1) At t1°C, the solubility curves of two solid substances A and B intersect at one point, and their solubilities are equal.

(2) The solubility of A increases with the increase of temperature. To change its unsaturated solution into a saturated solution, methods such as adding solute, cooling or evaporating the solvent can be used. Then A and B are wrong and C is correct; the saturated solution of A is It refers to a solution that cannot continue to dissolve A at a certain temperature, but is an unsaturated solution of other substances, so it can continue to dissolve other substances. D is correct.

On-site testing

Knowledge point 1: Solubility of solids and gases

1. At 20 ℃, the solubility of sodium chloride is 36 g. The person who misunderstood this sentence is ()

A． At 20°C, 100 g of water can dissolve up to 36 g of sodium chloride

B． At 20°C, 100 g of sodium chloride saturated solution contains 36 g of sodium chloride.

C. At 20°C, the mass ratio of water to sodium chloride in a saturated solution of sodium chloride is 100:36

D． At 20°C, dissolve 36 g of sodium chloride in 100 g of water, and the resulting solution is a saturated solution of sodium chloride at this temperature.

2. When you open the cap of a soda bottle, the reason why gas escapes from the water is ()

A． temperature rise

B． pressure decreases

C. liquid evaporates

D． thermal expansion

Knowledge point 2: The meaning and application of solubility curve

3. The solubility curve provides convenience for us to quantitatively describe the solubility of a substance. Please judge the following statements based on the solubility curve in Figure 7-2-4. The correct one is ()

A． Substance B is a soluble substance

B． At 40°C, the solubilities of the two substances are equal

C. At 60°C, 40 g of substance A is placed in 50 g of water, and the mass of the resulting solution is 90 g.

D． At 60 ℃, the saturated solution of two substances A and B with equal mass is cooled to 20 ℃. The one with more solid precipitated is B.

[ Analysis A maximum of 30 g of substance A can be dissolved, and the mass of the solution is 80 g; the solubility of substance A is greatly affected by temperature. When the mass of the saturated solution is equal, more solids will precipitate.

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Update Time: 2024-09-08

This template belongs to Chemistry courseware Cantonese Education Edition Ninth Grade Chemistry Volume 2 industry PPT template

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