"Measuring the pH of Rainwater" Chemistry and Sustainable Development PPT

Description

"Measuring the pH of Rainwater" Chemistry and Sustainable Development PPT

Part One: [Material Reading]

Material 1: Acid rain

Acid rain refers to rain, snow or other forms of precipitation with a pH less than 5.6. During the formation and falling process of rain, snow, etc., they absorb and dissolve sulfur dioxide, nitrogen oxides and other substances in the air, forming acidic precipitation with a pH lower than 5.6. Acid rain is mainly caused by man-made emissions of large amounts of acidic substances into the atmosphere.

Material 2: Types of acid rain

The anions in acid rain are mainly nitrate ions and sulfate ions. The types of acid rain are divided into three categories based on the concentration ratio of sulfate ions and nitrate ions, as follows:

(1) Sulfuric acid type or coal-fired type: sulfate/nitrate ≥ 3

(2) Mixed type: 0.5

(3) Nitric acid type or fuel type: sulfate/nitrate ≤ 0.5.

From this, the main influencing factors of acid rain can be preliminarily judged based on the type of acid rain in a place.

Material 3: The dangers of acid rain

Over the past decade, due to the increasing emissions of sulfur dioxide and nitrogen oxides, the problem of acid rain has become increasingly prominent. The main hazards are:

(1) Acid rain can cause soil acidification.

The soil contains a large amount of aluminum hydroxide. After the soil is acidified, it can accelerate the weathering of primary and secondary minerals containing aluminum in the soil and release a large amount of aluminum ions, forming aluminum compounds in a form that can be absorbed by plants. Long-term and excessive absorption of aluminum by plants can lead to poisoning and even death.

(2) Acid rain can induce plant diseases and insect pests and significantly reduce crop yields. Soybeans and vegetables are also susceptible to acid rain, leading to a decrease in protein content and yield.

(3) Acid rain can dissolve the hardened cement on the surface of non-metal building materials (concrete, mortar and lime sand bricks), causing voids and cracks, resulting in a reduction in strength and thus damaging the building.

Determining the pHPPT of rainwater, part 2: [Thinking about improvement]

1. What is the operation of using pH test paper to measure the pH of acid rain?

Tips: Take a piece of pH test paper and place it on a clean glass piece. Dip a clean glass rod into rainwater and drop it on the center of the test paper. When the color remains unchanged, compare it with the standard color card to determine the pH.

2. There are two identical rainwater samples. Two students measured the pH of the rainwater samples at different times. The data obtained are as follows:

What causes the pH changes in rainwater samples?

Tip: This is due to the oxidation of H2SO3 in rainwater by oxygen in the air: 2H2SO3+O2====2H2SO4, which increases the hydrogen ion concentration of the solution.

3. Use chemical equations to describe the formation process of sulfuric acid type acid rain.

Tip: Coal containing sulfur (replace with S) → SO2 → H2SO3 → H2SO4

①S+O2 SO2, ②SO2+H2O====H2SO3, ③2H2SO3+O2====2H2SO4.

4. Use chemical equations to describe the formation process of nitric acid type acid rain.

Tip: 2NO+O2====2NO2, 3NO2+H2O====2HNO3+NO.

5. What is the ionic reaction that occurs in material three (1)?

Tip:Al(OH)3+3H+====Al3++3H2O.

6. Based on the above analysis, what measures can you propose to prevent and control acid rain?

Tips: ① Develop new energy sources, such as hydrogen energy, solar energy, water energy, tidal energy, geothermal energy, etc.

② Use coal-fired desulfurization technology to reduce sulfur dioxide emissions.

③Industrial production exhaust gases must be treated to meet standards before being discharged.

④ Drive less and travel more by public transportation.

⑤ Use cleaner energy such as natural gas and use less coal.

Determining the pHPPT of rainwater, Part 3: [Migration Application]

The Climate Change Center of the China Meteorological Administration released the "China Climate Change Blue Book (2019)". The report pointed out that from 1992 to 2018, acid rain in China generally showed a weakening and decreasing trend; in 2018, the national average precipitation pH was 5.90, and the national average acid rain and strong acid rain frequencies were the lowest since 1992.

Acid rain is related to the rapid development of industrialization and the extensive use of fossil fuels. An industrial flue gas contains CO, CO2, N2, SO2 and other gases. The process of using Na2SO3 solution to absorb and recover SO2 is shown in the figure below.

(1) SO2 concentration: I________II (fill in ">" or "<").

(2) The material that can be recycled in this process is ________.

(3)The chemical equation of the main reaction in the above absorption process is ________.

(4) The desorption process requires heating, and a small amount is often produced during this process.

[Analysis] (1) (2) Flue gas contains gases such as CO, CO2, N2, SO2, etc., and absorbs sulfur dioxide through sodium sulfite, thus enriching sulfur dioxide. Sodium bisulfite easily decomposes when heated to generate sulfur dioxide, water and sodium sulfite, so SO2 concentration: I

Determining the pHPPT of rainwater, Part 4: [Compensation Training]

Students from a chemistry interest group in a school were divided into two groups to measure acid rain and the content of sulfur dioxide in the air.

The first group took samples of acid rainwater that had just fallen to the ground and conducted the following experiments:

① Soak a red rose petal in a portion of water sample;

② Add barium chloride solution dropwise to the rainwater sample, and a white precipitate will form;

(1) After a period of time, it was observed that the red color of the rose petals became lighter. The reason was ____________________.

(2)The ionic equation that generates white precipitate is ____________________________.

The second group plans to use the device shown in the figure to quantitatively analyze the SO2 content in the air:

(3) The experimental operation that should be performed before introducing air is _______________________________; the function of forming a spherical porous structure at the end of the catheter in the acidic KMnO4 solution is __.

(4) Known: 5SO2+2 ​​+2H2O====5 +2Mn2++4H+. With the continuous introduction of air, the color of the acidic potassium permanganate solution gradually becomes lighter until it fades, indicating that SO2 has ______________ properties.

(5) If the gas flow rate in the experiment is a L·min-1, the volume of the acidic KMnO4 solution is b L, and its concentration is c mol·L-1, and it takes 5 min from the gas introduction to the purple color to fade, then the air The content of sulfur dioxide in the product is ________g·L-1.

[Analysis] (1) If the color of rose petals becomes lighter, there are bleaching substances in the acid rain, that is, the SO2 in the acid rain has a bleaching effect.

(2) Acid rain contains sulfuric acid, which can combine with barium ions to form precipitation.

(3) Systems involving gas should be checked for air tightness first; the surface area of ​​the porous structure increases so that SO2 reacts with potassium permanganate as much as possible, which is conducive to the full absorption of SO2.

Determining the pHPPT of rainwater, Part 5: [Core Integration]

1. Transformation of nitrogen and its compounds

2. Sort out the main knowledge

(1) "Thunderstorm affects crops" involves reaction principles:

① N2+O2 2NO　②2NO+O2====2NO2

③ 3NO2+H2O====2HNO3+NO

(2) Industrial production method of ammonia: N2+3H2 2NH3

(3) Laboratory preparation method of ammonia:

① Principle: 2NH4Cl+Ca(OH)2 2NH3↑+CaCl2+2H2O

② Device: Same as using KMnO4 to produce O2

③ Collection method: downward air exhaust method

④ Inspection method:

a. Use moist red litmus paper to test and it will turn blue.

b. Put a glass rod dipped in concentrated hydrochloric acid close to the mouth of the bottle. A large amount of white smoke will be produced. The chemical equation for the reaction is NH3+HCl====NH4Cl.

⑤ Drying method: Soda lime, calcium oxide, and sodium hydroxide can be used, but concentrated sulfuric acid cannot be used.

Determining the pHPPT of rainwater, part 5: [Literacy transfer]

1. It is known that ammonia gas is insoluble in organic matter, such as CCl4. Which of the following statements about ammonia gas is correct ()

A. Ammonia can be dried with concentrated sulfuric acid

B. Ammonia is weakly alkaline when dissolved in water, so ammonia gas can turn wet phenolphthalein test paper blue.

C. Ammonia itself is not toxic, so when a large amount of liquid ammonia leaks, people do not need to take any preventive measures.

D. To absorb NH3, the device as shown in the figure can be used to prevent back suction.

[Analysis] Choose D. Ammonia is an alkaline gas and cannot be dried with acidic desiccants; moist phenolphthalein test paper will turn red when exposed to NH3; although ammonia cannot be called a toxic gas, it is often used because of its extremely high solubility and high volatility. It is adsorbed on the skin, mucous membranes and eye mucous membranes, causing irritation and inflammation. Therefore, when a large amount of liquid ammonia leaks, people must take certain preventive measures. For example, according to the characteristics of ammonia's low density, you can run away in the direction of low terrain and headwind. Accident area, so A, B, and C are all wrong. Carbon tetrachloride is an oily liquid, and ammonia does not dissolve in it. This prevents back suction. Item D is correct.

2. Which of the following phenomena or facts cannot be explained by the same principle ()

A. Store concentrated nitric acid and chlorine water in brown reagent bottles

B. Sodium sulfide and sodium sulfite solids deteriorate after being exposed to the air for a long time.

C. Both iron and platinum are insoluble in concentrated nitric acid at room temperature.

D. Both SO2 and Na2SO3 solutions can make chlorine water fade.

[Analysis] Choose C. Concentrated nitric acid decomposes easily when exposed to light and should be stored in a brown reagent bottle; chlorine water decomposes when exposed to light and should be stored in a brown reagent bottle. The same principle can be used to explain, A does not meet the meaning of the question. Sodium sulfide has reducing properties and is easily oxidized and deteriorated by oxygen in the air; sodium sulfite is reducing and is easily oxidized and deteriorated by oxygen in the air. It can be explained by the same principle. B does not meet the meaning of the question. Iron is passivated when it encounters concentrated nitric acid at room temperature; platinum is weakly reactive and does not react with concentrated nitric acid. It cannot be explained by the same principle. C is in line with the meaning of the question. SO2 has reducing properties and can undergo an oxidation-reduction reaction with chlorine water to cause chlorine water to fade; Na2SO3 has reducing properties and can undergo an oxidation-reduction reaction with chlorine water to cause chlorine water to fade. The same principle can be used to explain it. D does not meet the meaning of the question.

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