"Amount of Substances" Important elements in seawater - sodium and chlorine PPT (Lesson 3: Amount and concentration of substances)

Description

"Amount of Substances" Important elements in seawater - sodium and chlorine PPT (Lesson 3: Amount and concentration of substances)

Part One: Learning Objectives

Curriculum Standards

1. Understand the meaning and application of quantity and concentration of substances, and appreciate the important role of quantitative research in chemical science.

2. Be able to understand the composition of matter and its chemical changes based on the amount of matter, and use the relationship between the amount of matter, molar mass, gas molar volume, and the amount and concentration of matter to perform simple calculations.

3. Able to prepare solutions with a certain concentration of substances.

core competencies

1. Concept of change: Understand the important role of substance concentration in quantitative chemical research.

2. Macroscopic identification and microscopic analysis: Establish the concept of quantity and concentration of substances, and quantitatively understand the composition of substances and chemical changes of substances based on the quantity and concentration of substances.

3. Scientific inquiry: Select common experimental instruments, devices and reagents to prepare a solution with a certain substance concentration.

Amount of substance PPT, part 2 content: Knowledge point 1: Amount concentration of substance and its calculation

1. Concept: __________ of solute B contained in __________ solution, the symbol is _____, and the common unit is _______ or __________.

2. Expression: cB=nBV, where "V" refers to the volume of the solution, not the volume of the solvent.

3. Simple calculation

(1) If the concentration of a certain ion in the solution is known, find the concentration of other ions.

The ratio of the amount and concentration of anionic and cationic substances in a solution = the ratio of the number of ions in the chemical composition.

For example: in Na2SO4 solution, c(SO2-4)=1mol·L-1, then c(Na+)=__________, c(Na2SO4)=__________.

(2) Calculate the concentration by knowing the mass of the solute in a certain volume of solution

For example: 2.0g NaOH solid is dissolved in water to make a 500mL solution, then the concentration of the solution is ____________________.

(3) Under standard conditions, a certain volume of gas dissolves in water to form a VL solution to calculate the concentration.

For example: under standard conditions, 11.2L HCl gas is dissolved in water to form a 200mL solution, then the concentration of the solution is ______________.

Troubleshooting

1. Conversion of substance concentration and solute mass fraction

(1) Conversion formula: cB＝1000ρwMmol·L－1

M: molar mass of solute B (unit: g·mol-1); ρ: solution density (unit: g·mL-1); w: mass fraction of solute.

2. Calculation of solution dilution and mixing

(1) Dilution of concentrated solution

①The amount of solute substance remains unchanged: c (concentrated) V (concentrated) = c (dilute) V (dilute);

②The mass of the solute remains unchanged: m (concentrated)·w (concentrated) = m (dilute)·w (dilute);

③The mass of the solution is conserved: m (dilute) = m (concentrated) + m (water) (volume is generally not conserved).

(2) Mixing of two solutions of the same solute

①The amount of solute material remains unchanged: c1V1+c2V2=c (mixed)·V (mixed);

②The mass of the solute remains unchanged: m1w1+m2w2=m(mixed)•w(mixed).

use as you learn

The meaning of 1.1 mol·L-1 sulfuric acid solution is ()

A. 1L of water contains 1 mol of sulfuric acid

B． 1L solution contains 1molH+

C. A solution prepared by dissolving 98g sulfuric acid in 1L water

D． After taking out 500mL from 1L of this solution, the concentration of the remaining solution is still 1mol·L-1

2. Which of the following statements is correct ()

A. The concentration of the solution formed by dissolving 1 mol NaCl in 1 L of water is 1 mol·L-1

B． Under standard conditions, the volume of the solution formed by dissolving 22.4L HCl gas in 1L water is 1L.

C. Under standard conditions, 33.6L HCl gas is dissolved in water to form 1L solution, and the substance concentration is 1.5mol·L-1

D． 1molCaCl2 is dissolved in water to form 1L solution. The c(Cl-) in the resulting solution is equal to 1mol·L-1

Amount of substance PPT, part 3 content: Knowledge point 2: Preparing a solution with a certain amount and concentration of a substance

1. Volumetric flask: used to accurately prepare solutions with a certain concentration of a certain substance.

(1) Structural features: A thin-necked, pear-shaped flat-bottomed glass bottle with a ground glass or plastic stopper at the mouth, marked with ______ and volume.

(2) Common specifications: 50mL, 100mL, 250mL, 500mL, 1000mL.

(3) Precautions

① The volumetric bottle stopper must be tied to the bottle neck with a strong string to prevent damage or loss.

② Before use, first check whether the volumetric flask is intact and whether there is water leakage at the mouth of the bottle.

Leak detection method: Pour a certain amount of water into the volumetric flask and close the stopper. Hold the cork with your index finger, hold the bottom of the bottle with your other hand, turn the bottle upside down and check for leaks. If there is no water leakage, stand the bottle upright and rotate the stopper 180° before plugging it tightly. Then turn the bottle upside down and observe whether there is water leakage. The volumetric flask can only be used if there is no water leakage.

③Do not use volumetric flasks to dissolve solids or dilute concentrated solutions.

④ Volumetric flasks cannot be used as reaction vessels or for long-term storage of solutions.

⑤ Select the volumetric flask according to the principle of "large and close", that is, the volume of the solution to be prepared is equal to or slightly smaller than the volume of the volumetric flask.

⑥After use, the volumetric flask should be washed and dried. (Glass ground bottle stoppers should place a piece of paper between the stopper and the bottle mouth to prevent the stopper from adhering to the bottle mouth)

2. Prepare a solution with a certain substance concentration (to prepare 100mL1.00mol•

L-1NaCl solution as an example)

(1) Main instruments: pallet balance, medicine spoon, beaker, measuring cylinder, ____________, ____________, ______________.

(2)Experimental steps

Troubleshooting

Error Analysis for Preparing a Concentration Solution of a Certain Substance

1. Principle basis

Judgment based on cB=nBV=mM·V. When other conditions remain unchanged:

(1) Factors that increase (or decrease) m cause cB to be larger (or smaller).

(2) Factors that increase (or decrease) V cause cB to be smaller (or larger).

2. Error Analysis

3. Illustration of the error caused by looking up or down at the scale line when setting the volume

(1) Look up at the scale line (Picture A). Since water is added based on the scale line during operation, the first thing you see when looking from bottom to top is the scale line. The scale line is lower than the actual height of the liquid level, so the amount of water added is too much, resulting in a larger solution volume and a smaller concentration.

(2) Look down at the scale line (Figure B). Just the opposite of looking up at the scale line, the scale line is higher than the actual height of the liquid level, so the amount of water added is too small, resulting in a smaller solution volume and a larger concentration.

use as you learn

1. Which of the following statements about volumetric flasks is incorrect ()

A. Volumetric flasks are generally marked with specifications, temperature and scale lines.

B． Volumetric flasks should be checked for leaks before use

C. Concentrated solutions can be diluted directly in volumetric flasks

D． The volumetric flask cannot hold the prepared solution for a long time and should be packed in reagent bottles in time.

2. Using solid samples to prepare a solution with a certain substance concentration requires operations such as weighing, dissolving, transferring the solution, and setting the volume. The operating specifications corresponding to the following diagrams are ()

3. The solution prepared below has a higher concentration ()

A. When preparing hydrochloric acid, use a graduated cylinder to measure hydrochloric acid and read from above when measuring it.

B． When preparing hydrochloric acid to constant volume, look up at the graduated line of the volumetric flask.

C. When weighing 4.0g NaOH to prepare 1000mL 0.1mol·L-1NaOH solution, the weight was placed on the left plate by mistake.

D． After NaOH is dissolved, pour it into the volumetric flask without cooling, and add water to the mark.

Quantity of matter PPT, part 4 content: Qualification examination training

1. In the blood test sheet of Xiao Ming's physical examination, glucose was 5.9mmol/L. The physical quantity representing the physical examination index is ()

A. Amount of substance B. quantity concentration of substance

C. Quality fraction D. Molar mass

2. The amount of solute in the following solution is 0.1 mol·L-1 ()

A. 1L solution containing 4gNaOH

B． 1L solution containing 0.1gNaOH

C. 0.5L solution containing 0.2molH2SO4

D． Pour 98g of H2SO4 into 1L of water

3. In the laboratory, 950 mL of 2 mol·L-1 NaOH solution needs to be prepared. The specifications of the volumetric flask that should be used during preparation and the mass of NaOH to be weighed are ()

A. 950mL, 96.0g B． 500mL, 80.0g

C. 1000mL, 80.0g D. 1000mL, 76.0g

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Update Time: 2024-11-02

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