"Acidic Solutions and Alkaline Solutions" Initial Acids, Bases and Salts PPT Courseware

"Acidic Solutions and Alkaline Solutions" Initial Acids, Bases and Salts PPT Courseware

Simple classification of substances:

substance

Mixture A substance composed of two or more substances (such as air, solution, etc.)

Pure substance

A substance composed of a substance. (such as oxygen, carbon dioxide, potassium permanganate, etc.)

Elemental metal element (such as iron, magnesium, etc.)

Non-metallic elements (such as carbon, oxygen, etc.)

Pure substances composed of the same elements

compound oxide

Composed of two elements, one of which is a compound of oxygen

Other compounds (acid and alkali salts, etc.)

1. Acidic solution and alkaline solution

In daily life, what substances have left a "sour impression" on you?

life inspiration

The wine tastes spicy - there is ethanol in the wine

Sugar water has sweetness - there is sucrose in sugar water

Salt water has a salty taste - Salt water has sodium chloride

Soda water has a bitter taste - it contains alkaline substances

Vinegar and yogurt have a sour taste - they contain acidic substances

Normally, you are not allowed to taste the taste of chemical reagents, so how do we determine whether a substance is acidic or alkaline?

Recall: What do you see when you pass carbon dioxide into purple litmus solution?

CO2+H2O==H2CO3

Can solutions of vinegar, vermicelli, and other sour substances turn purple litmus test solution red?

2. The acidity and alkalinity of the solution

Litmus or phenolphthalein test solution can be used to test the acidity and alkalinity of a certain solution, but can the acidity and alkalinity of two solutions be compared? For example: vinegar and dilute hydrochloric acid are both acidic. Which one is more acidic?

Vermicelli juice, white vinegar, and dilute hydrochloric acid have different acidic strengths, and lime water, ammonia water, and soapy water have different alkaline strengths. Therefore, people use pH to express the degree of acidity or alkalinity of a solution.

Notice

The smaller the pH value of an acidic solution, the stronger the acidity; conversely, the larger the pH value, the weaker the acidity (inverse ratio).

The larger the pH value of an alkaline solution, the stronger the alkalinity, and conversely, the smaller the pH value, the weaker the alkalinity (proportional).

Observe the picture below and fill in the blanks below:

1. The acidity and alkalinity of the solution: pH=7, the solution is ____; pH<7, the solution is ____; pH>7, the solution is ____.

2. The relationship between the pH of the solution and the acidity and alkalinity of the solution: the greater the pH, ________; the smaller the pH, ________.

3. The relationship between the acidity and alkalinity of the solution and life activities

Reading materials:

The pH of body fluids in healthy people must be maintained within a certain range. If the pH of body fluids exceeds the normal range, it will lead to physiological dysfunction or disease, or even "acidosis." If there is too much gastric acid secretion, the pH of the gastric juice drops below the normal level, and symptoms such as stomach pain may easily occur.

Reading materials:

Most crops are suitable for growing in soil that is close to neutral (pH between 6.5 and 7.5). Soil that is too acidic (pH less than 4) or too alkaline (pH greater than 8) is not suitable for the growth of crops.

When a certain mass fraction of an acidic or alkaline solution is diluted with water, the relationship between the pH of the solution and the volume (V) of the added water is:

For alkaline solutions, after adding water, the alkalinity of the solution weakens and the pH decreases, gradually approaching 7, but it will never equal 7.

For acidic solutions, after adding water, the acidity of the solution weakens and the pH increases, gradually approaching 7, but it will never equal 7.

Can you come up with the answer?

1. Commonly used acid-base indicators in laboratories include ( ) test solution and ( ) test solution, among which ( ) can change color when exposed to acid or alkali.

2. Acid-base indicators are commonly used in laboratories to test the solution ( ), and pH is commonly used to measure the solution ( ).

3. Of the following liquids in the normal human body, the one that is acidic and the most acidic is ().

A.Plasma B.Pancreatic juice C.Gastric juice D.Saliva

4. Benzoic acid can be used as a food preservative, and its acidity is stronger than acetic acid. Which of the following assumptions about the properties of benzoic acid is unreasonable ( ).

A. The pH of the benzoic acid solution is greater than 7. B. The pH of the benzoic acid solution is less than 7.

C. Benzoic acid can turn purple litmus test solution red

D. Benzoic acid cannot change color of colorless phenolphthalein test solution

Improvement exercises:

1. The following pH value indicates the most acidic solution:

A, Ph=0 B, pH =1

C, pH =7 D, pH =14

2. Doctors remind patients with hyperacidity to eat less apples. Then the pH of apples:

A, greater than 7 B, less than 7

C. Equal to 7 D. Unable to judge

3. When sodium hydroxide solution is added dropwise to dilute hydrochloric acid, the correct pH change of the solution is:

pH and human health

The pH value of human body fluids is normal when it is 7.35~7.45;

When the pH value of human body fluids is <7.35, it is in a sub-healthy state;

When the pH value of human body fluids = 6.9, it becomes a vegetative state;

Death occurs when the pH value of human body fluids is 6.85~6.45.

Simple classification of acid-reducing foods

Acidic foods: animal foods other than milk

Alkaline foods: plant foods other than whole grains

Neutral food: oil, salt, coffee, tea, etc.

Acid-base classification of common foods

Strong acidity - egg yolks, cheese, pastries made with white sugar, persimmons, dried bonito, etc.

Medium acidity - ham, bacon, chicken, pork, eel, beef, bread, wheat, butter, etc.

Weakly acidic - rice, peanuts, beer, seaweed, loach, etc.

Weakly alkaline - red beans, radishes, apples, cabbage, onions, tofu, etc.

Medium alkaline - soybeans, carrots, tomatoes, bananas, oranges, pumpkins, strawberries, egg whites, prunes, lemons, spinach, etc.

Strongly alkaline - grapes, wine, kelp sprouts, kelp, etc. Especially for natural green algae, the best time to drink is from 9 a.m. to 11 a.m.

common acids common bases

Nitric acid HNO3 Sodium hydroxide NaOH

Sulfate H2SO4 Calcium hydroxide Ca(OH)2

Hydrochloric acid HCl Ammonia NH3·H2O

Carbonic acid H2CO3

Common acidic salt solutions Common alkaline salt solutions

Ammonium chloride NH4Cl Sodium carbonate Na2CO3

Copper sulfate CuSO4 Sodium bicarbonate NaHCO3

Ferric chloride FeCl3

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