"Common Acids and Bases" Acids and Bases PPT Courseware 5

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"Common Acids and Bases" Acids and Bases PPT Courseware 5

1. Conductivity of solution

Experiment on the conductivity of the following substances

Can solid NaCl conduct electricity? Why? What about H2O?

Can NaCl solution? Why? What about the aqueous solution of HCl?

Do all solutions conduct electricity?

Materials that can conduct electricity must contain freely moving charged particles.

Metals conduct electricity - metals have free-moving electrons

Acid, alkali, and salt solutions can conduct electricity

think:

1. When acids, alkalis, and salts dissolve in water, what kind of particles do they exist in water?

2. Does ionization require electricity?

3. What are the same particles that acids contain in aqueous solutions?

4. What are the same particles contained in aqueous solutions of bases?

5. What is the reason why acid and alkali solutions can cause the indicator to change color?

Acid: A compound in which all cations produced by ionization are hydrogen ions.

Base: A compound in which the anions produced by ionization are all hydroxide ions.

Salt: A compound that ionizes to form metal ions and acid ions.

2. Acid-base indicator

A substance that can react with acid or alkali solutions and display different colors is called an acid-base indicator. Commonly used acid-base indicators include litmus and phenolphthalein.

3. Expression of solution acidity and alkalinity - pH

The acidity and alkalinity of a solution can be measured using acid-base indicators.

Acid-base indicators can only measure whether a solution is acidic or alkaline, but cannot measure the acidity or alkalinity of a solution.

The degree of acidity and alkalinity of a solution is called the pH of the solution. Often expressed as pH.

The pH range is usually between 0 ~ 14

The pH of some substances in daily life, (P62 Figure 10-18)

Substances with a pH less than 7 include: lemons, apples, oranges, vinegar, soy sauce, watermelon, radish, and detergent.

Substances with a pH greater than 7 include: toothpaste, soap, plant ash leaching solution, kitchen cleaners, milk, and egg white, which are close to neutral

1. Determine the categories of the following substances:

Copper sulfate hydrochloric acid

Sodium hydroxide Magnesium chloride

carbonic acid barium hydroxide

Ferrous sulfate Ammonia

Ammonium chloride sodium bicarbonate

water copper oxide

2. The three bottles of colorless liquid that have lost their labels are dilute H2SO4, distilled water, and NaOH solution. The reagent that can distinguish them at once is ( )

A. Phenolphthalein B. Iron flakes

C. Litmus test solution D. Carbon dioxide gas

3. The three bottles of colorless liquids that have lost their labels are dilute HCl, distilled water, and NaOH solution. Can they be identified using phenolphthalein test solution? (Hint HCl + NaOH NaCl + H2O)

chemical properties of acids

1. React with acid-base indicators

① Acid solution can turn purple litmus solution into red

② The acid solution cannot change the color of the colorless phenolphthalein test solution

NOTE: What changes color is the indicator solution.

【experiment】

(1) Put two iron nails (polished with sandpaper) into the test tube, and then add 1mL of dilute hydrochloric acid (or dilute sulfuric acid).

(2) Put a small amount of zinc particles in the test tube, and then add 1mL of dilute hydrochloric acid (or dilute sulfuric acid).

2. React with certain metals

Metal + acid → salt + hydrogen

Conditions: ① In the order of metal activity, the metal ranked before hydrogen can replace the hydrogen in the acid.

②The acid is mainly HCl and dilute H2SO4.

Chemical properties of bases

think:

1. What alkalis do you know?

2. Do you remember the use of clarified lime water?

Experimental exploration 1

Add 1-2 drops of litmus test solution and phenolphthalein test solution to the sodium hydroxide solution and clarified lime water respectively.

Phenomenon

Purple litmus test solution turns blue and phenolphthalein test solution turns red.

Conclusion 1

Alkaline solutions can react with acid-base indicators, turning purple litmus test solution blue and phenolphthalein test solution red.

Experimental exploration 2

Quickly pour the sodium hydroxide solution into the plastic bottle that collected carbon dioxide, cap the bottle and shake;

Add a small amount of clarified limewater to a small test tube and blow air into the clarified limewater through a straw.

feedback exercise

1. The calcium hydroxide solution dripping with phenolphthalein reacts completely with each of the following substances. The solution still appears red ( )

A. Dilute sulfuric acid B. Copper chloride solution

C. Potassium carbonate solution D. Carbon dioxide

2. Chemical reactions are often accompanied by some phenomena, but the reaction between CO2 and NaOH solution has no obvious phenomenon. In order to illustrate the reaction between CO2 and NaOH through some phenomena, a certain class of students was divided into two groups and conducted the following research experiments:

(1) The first group of students put a test tube collecting CO2 upside down in a beaker containing a saturated NaOH solution (as shown in the picture on the right) and saw the liquid level in the test tube rising. This phenomenon occurs because it occurs inside and outside the test tube ( )

A． Temperature difference b. gravity difference

C. Pressure difference D. Poor buoyancy

(2) The second group of students got inspiration from this and designed the following experimental devices for investigation:

Phenomenon A is _____________, phenomenon B is _____________,

C phenomenon is___________.

(3) After analysis and discussion, the students believed that there may be two reasons for the rising liquid level in the first group of experiments. One is because CO2 reacts with NaOH in the solution and consumes CO2. You think the other reason is _______________.

(4) In order to further confirm that the reaction between CO2 and NaOH solution has occurred, they designed the following plan: take the solution after the above experiment, the first group of students added ____________ dropwise, and the phenomenon was ____________________; the second group of students added ____________ dropwise , the phenomenon is _______________. Although they saw different phenomena, they could all confirm that CO2 and NaOH solution had reacted.

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Update Time: 2024-10-01

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