"Quantitative Expression of Solution Composition" Solution PPT Courseware

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"Quantitative Expression of Solution Composition" Solution PPT Courseware

Key points review

1. The characteristics of the solution are ( )

A Transparent B Colorless C Stratified D Uniform and stable

2. The density measured at the upper part of a cup of NaCl solution is 5 g/cm3, then the density measured at the lower part is ( )

A <5 B >5 C equal to 5 D less than 5 or greater than 5

3. What can be used as a solute ( )

A Solid B Liquid C Gas D Solid, liquid or gas can be used

Mass of solution =___________+___________

1. Completely dissolve 10 grams of potassium nitrate in 90 grams of water to form a ( ) gram solution

2. If the mass of water in 100 grams of potassium chloride solution is 89 grams, then the mass of potassium chloride ( ) grams

3. Dissolve 25 grams of sodium sulfate in ( ) grams of water to form 200 grams of sodium sulfate solution.

New knowledge guide

1.3 g of table salt is dissolved in 20 g of water. What is the mass of salt water formed?

Tip: 3 g+20 g=23 g

2. Put 5 g of white sugar in 15 g of water, and put 10 g of white sugar in 40 g of water. Which sugar water is sweeter?

hint:

The sugar content in the first sugar water is:

The sugar content in the second type of sugar water is:

So the first sugar water is sweeter.

Mass fraction of solute:

Concept: Ratio of solute mass to solution mass

Formula: Mass fraction of solute

mass of solute

= ————— × 100�

quality of solution

mass of solute

＝————————×100�

Mass of solute + mass of solvent

Meaning: How many parts of mass of solute are there in 100 parts of mass of solution.

Continue to explore

Dilute 50g of 20% potassium nitrate solution with water to a solution with a mass fraction of 10%. Find the mass of water used in dilution.

Essence: The mass of the solute remains unchanged before and after dilution

Mass of solute before dilution = Mass of solute after dilution

50 g × 20% = (50 g + x) × 10%

Solution: Let the mass of water added during dilution be x

50 g × 20% = (50 g +x) × 10%

x=50 g

Answer: The mass of water used for dilution is 50 g.

Note: When two solutions are mixed, the masses can be added, but the volumes cannot be added.

2. Preparation of solution

Prepare 50 grams of sodium chloride solution with a mass fraction of 16%.

Now that you want to prepare this sodium chloride solution, please think about how to do it? Please summarize the experimental steps and corresponding experimental instruments.

Instruments: tray balance, medicine spoon, measuring cylinder, rubber dropper, beaker, glass rod

step:

(1) Calculation: Calculate the required amount of solute and solvent according to the preparation requirements

(Calculate mass for solids and volume for liquids)

(2) Weighing: Use a tray balance to weigh out the required solute, and then use a measuring cylinder to get the required solvent.

(3) Dissolution: Mix the solute and the solvent and stir until the solute is completely dissolved.

(4) Bottle storage and label: Put the prepared solution into the reagent bottle and label it.

Prepare 50g of 16% sodium chloride solution

Step 1: Calculate the mass of sodium chloride and volume of water required.

The mass of sodium chloride required: 50g×16%=8g

The quality of distilled water required: 50g-8g=42 g

Volume of distilled water required: 42g/1g/mL=42mL

Step 2: Use a balance to weigh 8g of sodium chloride, and use a graduated cylinder to measure 42mL of water.

Step 3: Put the weighed 8g of sodium chloride into the beaker, pour the measured 42mL of water, and stir with a glass rod to completely dissolve the sodium chloride.

Step 4: Bottle and label (indicate the drug name and solute mass fraction).

50g of 16% sodium chloride solution is now prepared.

problem analysis

If the solute mass fraction of the prepared solution is slightly greater or less than 16%, what do you think are the possible reasons?

1. The sodium chloride is weighed incorrectly.

2. When measuring water with a measuring cylinder, look down (or look up) to read.

3.……

What is the "degree" of liquor?

Liquor packages are marked with “degree”, such as 53-degree Maotai. The "degree" of liquor actually refers to the alcohol content in liquor. The content here does not refer to the mass fraction, but the volume fraction, that is, the volume ratio of alcohol to water is 53:47.

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"Quantitative Expression of Solution Composition" Solution PPT Courseware 3 Knowledge Review Knowledge Point 1 Regarding the calculation of solute mass fraction The solute mass fraction is the ratio of _______ mass and _______ mass. Relevant formulas: ①Solute mass fraction = solute mass/solution mass 100%..

"Quantitative Expression of Solution Composition" Solution PPT Courseware 2:

"Quantitative Expression of Solution Composition" Solution PPT Courseware 2 The more salt is added, the saltier the solution will be, and the greater the concentration will be. The concentration or dilution of a solution refers to the relative amount of solute content. It cannot accurately indicate the amount of solute contained in a certain amount of solution. How to express exactly...

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Update Time: 2024-10-19

This template belongs to Chemistry courseware Beijing Curriculum Reform Edition Ninth Grade Chemistry Volume 2 industry PPT template

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