"Concentration of Solution" Solution PPT Courseware

Description

"Concentration of Solution" Solution PPT Courseware

learning target

1. Master a method of expressing the composition of a solution - the mass fraction of solute.

2. Ability to perform simple calculations of solute mass fraction.

3. Preliminarily learn to prepare solutions with a certain solute mass fraction.

mass fraction of solute

1. Definition: The mass fraction of a solute is the ratio of the mass of the solute to the mass of the solution.

2.Expression:

Mass fraction of solute = mass of solute/mass of solution × 100% = mass of solute/mass of solute + mass of solvent × 100%

I will do it

It is known that 50g of sodium chloride solution contains 5g of sodium chloride. Calculate the mass fraction of sodium chloride in the solution.

Solution: The mass fraction of sodium chloride in this solution

=5g/50g×100%

=10%

Answer: The mass fraction of sodium chloride in this solution is 10%.

For example, how many kilograms of sodium chloride and water are needed to prepare 150kg of 16% sodium chloride solution?

Solution: The mass of NaCl contained in 150kg of 16% sodium chloride solution is

150kg×16%=24kg

The mass of water required is 150kg-24kg= 126kg

Answer: To prepare 150kg of 16% sodium chloride solution, 24kg of sodium chloride and 126kg of water are needed.

Comparison of solute mass fraction and solubility

The mass fraction of solute 36% means: 100g solution contains 36g solute.

The solubility of a solute at T°C is 36g. This means that at T°C, 100g of water can dissolve up to 36g of the solute.

Solute mass fraction of saturated solution = solubility/100g + solubility × 100%

dilution of solution

Chemistry laboratories currently have 98% concentrated sulfuric acid, but dilute sulfuric acid is often used in experiments. It is necessary to dilute 50g of concentrated sulfuric acid with a mass fraction of 98% into 20% sulfuric acid. What mass of water is required?

Principle: The mass of the solute remains unchanged before and after dilution, and the required mass of water is:

50g×98%/20% - 50g=195g

Prepare solution

General steps: calculation, weighing (or measuring), dissolving, bottling and storage

Instruments used to prepare solutions with solids (taking solid NaCl as an example): tray balance, beaker, glass rod, measuring cylinder, rubber-tipped dropper, medicine spoon

Instruments used to prepare solutions with liquids: (such as diluted concentrated sulfuric acid) beakers, glass rods, measuring cylinders, rubber-tipped droppers

Classic examples

Knowledge point 1. Mass fraction of solute

[Typical Example 1] (2010·Kandian High School Entrance Examination) Peracetic acid is a commonly used disinfectant. There is an existing peracetic acid solution with a solute mass fraction of 15%. Please fill in the blanks:

⑴100g of this solution contains ________g of solute.

⑵ Add 200g of water to 100g of this solution, and the solute mass fraction of the resulting solution is ________.

⑶ Mix 100g of this solution with 100g of 5% peracetic acid solution. The solute mass fraction of the resulting solution is _____.

Knowledge point 2. Preparation of solution

[Typical Example 2] (2010 Enshi High School Entrance Examination) To prepare 100g of sodium chloride solution with a solute mass fraction of 10%, which of the following operations is correct ( )

A． Place 10g of sodium chloride solid directly on the tray of the balance and weigh it

B． When measuring 90ml of water, read from above

C. To speed up the dissolution of the solid, stir the solution with a thermometer

D. Pour the prepared solution into a narrow-mouth bottle, cap the bottle tightly, and label it

Intelligent training

1. Put 10 grams of sodium chloride into 40 grams of water. After it is completely dissolved, the mass fraction of sodium chloride in the solution is ( )

A． 10% b. 20% c. 25%D. 33.3%

2. Cool the 70°C saturated sodium nitrate solution to 10°C and crystals will precipitate (the crystals do not contain water). Which of the following quantities has not changed ( )

A. Solubility of sodium nitrate B. Mass of solute in solution

C. The mass of the solvent in the solution D. The mass fraction of the solute in the solution

3. (2010 Hainan High School Entrance Examination) To prepare a sodium chloride solution with a certain solute mass fraction, which of the following operations is wrong ( )

4. (2010·Mianyang High School Entrance Examination) Under the condition that the temperature remains unchanged, the following method to double the mass fraction of the solute is the most feasible one ( )

A. Evaporate 10g of water from 20g of saturated potassium nitrate solution

B. Evaporate 10g of water from 20g of unsaturated potassium nitrate solution

C. Add 5g of 40% potassium nitrate solution to 10g of 10% potassium nitrate solution

D. Add 10g potassium nitrate solid to 10g potassium nitrate unsaturated solution

Class summary

Quantitative representation of solution composition—mass fraction of solute

1. Mass fraction of solute: The mass fraction of solute is the ratio of the mass of solute to the mass of solution.

Expression: Mass fraction of solute = mass of solute/mass of solution × 100% = mass of solute/mass of solute + mass of solvent × 100%

2. Preparing a solution with a certain solute mass fraction generally requires steps such as calculation, weighing (or measuring), dissolving (or diluting), bottling and storage.

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Update Time: 2024-06-27

This template belongs to Chemistry courseware People's Education Press Ninth Grade Chemistry Volume 2 industry PPT template

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