Carbon dioxide is a characteristic of a substance. Carbon dioxide in industry, its production and application. What do aquarium plants need?

Soda, volcano, Venus, refrigerator - what do they have in common? Carbon dioxide. We have collected for you the most interesting information about one of the most important chemical compounds on Earth.

What is carbon dioxide

Carbon dioxide is known mainly in its gaseous state, i. as carbon dioxide with the simple chemical formula CO2. In this form, it exists under normal conditions - at atmospheric pressure and "normal" temperatures. But at increased pressure, over 5,850 kPa (such, for example, the pressure at a sea depth of about 600 m), this gas turns into a liquid. And with strong cooling (minus 78.5 ° C), it crystallizes and becomes the so-called dry ice, which is widely used in trade for storing frozen foods in refrigerators.

Liquid carbon dioxide and dry ice are produced and used in human activities, but these forms are unstable and break down easily.

But gaseous carbon dioxide is ubiquitous: it is released during the respiration of animals and plants and is an important part of the chemical composition of the atmosphere and ocean.

Properties of carbon dioxide

Carbon dioxide CO2 is colorless and odorless. Under normal conditions, it has no taste. However, when inhaling high concentrations of carbon dioxide, a sour taste can be felt in the mouth, caused by the fact that carbon dioxide dissolves on mucous membranes and in saliva, forming a weak solution of carbonic acid.

By the way, it is the ability of carbon dioxide to dissolve in water that is used to make sparkling waters. Bubbles of lemonade - the same carbon dioxide. The first apparatus for saturating water with CO2 was invented as early as 1770, and already in 1783, the enterprising Swiss Jacob Schwepp began the industrial production of soda (the Schweppes trademark still exists).

Carbon dioxide is 1.5 times heavier than air, so it tends to “settle” in its lower layers if the room is poorly ventilated. The “dog cave” effect is known, where CO2 is released directly from the ground and accumulates at a height of about half a meter. An adult, getting into such a cave, at the height of his height does not feel an excess of carbon dioxide, but dogs find themselves right in a thick layer of carbon dioxide and are poisoned.

CO2 does not support combustion, so it is used in fire extinguishers and fire suppression systems. The trick with extinguishing a burning candle with the contents of an allegedly empty glass (but in fact - carbon dioxide) is based precisely on this property of carbon dioxide.

Carbon dioxide in nature: natural sources

Carbon dioxide is produced in nature from various sources:

• Breathing of animals and plants.
  Every schoolchild knows that plants absorb carbon dioxide CO2 from the air and use it in photosynthesis. Some housewives are trying to atone for shortcomings with an abundance of indoor plants. However, plants not only absorb but also release carbon dioxide in the absence of light as part of the respiration process. Therefore, a jungle in a poorly ventilated bedroom is not a good idea: at night, CO2 levels will rise even more.
• Volcanic activity.
  Carbon dioxide is part of volcanic gases. In areas with high volcanic activity, CO2 can be released directly from the ground - from cracks and faults called mofet. The concentration of carbon dioxide in mofet valleys is so high that many small animals die when they get there.
• decomposition of organic matter.
  Carbon dioxide is formed during combustion and decay of organic matter. Volumetric natural emissions of carbon dioxide accompany forest fires.

Carbon dioxide is "stored" in nature in the form of carbon compounds in minerals: coal, oil, peat, limestone. Huge reserves of CO2 are found in dissolved form in the world's oceans.

The release of carbon dioxide from an open reservoir can lead to a limnological catastrophe, as happened, for example, in 1984 and 1986. in lakes Manun and Nyos in Cameroon. Both lakes were formed on the site of volcanic craters - now they are extinct, but in the depths, volcanic magma still emits carbon dioxide, which rises to the waters of the lakes and dissolves in them. As a result of a number of climatic and geological processes, the concentration of carbon dioxide in the waters has exceeded the critical value. A huge amount of carbon dioxide was released into the atmosphere, which, like an avalanche, descended along the mountain slopes. About 1,800 people became victims of limnological disasters on the Cameroonian lakes.

Artificial sources of carbon dioxide

The main anthropogenic sources of carbon dioxide are:

• industrial emissions associated with combustion processes;
• automobile transport.

Despite the fact that the share of environmentally friendly transport in the world is growing, the vast majority of the world's population will not soon be able (or willing) to switch to new cars.

Active deforestation for industrial purposes also leads to an increase in the concentration of carbon dioxide CO2 in the air.

CO2 is one of the end products of metabolism (the breakdown of glucose and fats). It is secreted in the tissues and carried by hemoglobin to the lungs, through which it is exhaled. In the air exhaled by a person, there is about 4.5% carbon dioxide (45,000 ppm) - 60-110 times more than in the inhaled air.

Carbon dioxide plays an important role in the regulation of blood supply and respiration. An increase in the level of CO2 in the blood causes the capillaries to expand, allowing more blood to pass through, which delivers oxygen to the tissues and removes carbon dioxide.

The respiratory system is also stimulated by an increase in carbon dioxide, and not by a lack of oxygen, as it might seem. In fact, the lack of oxygen is not felt by the body for a long time, and it is quite possible that in rarefied air a person will lose consciousness before he feels a lack of air. The stimulating property of CO2 is used in artificial respiration devices: there, carbon dioxide is mixed with oxygen to "start" the respiratory system.

Carbon dioxide and us: why is CO2 dangerous?

Carbon dioxide is as essential to the human body as oxygen. But just like with oxygen, an excess of carbon dioxide harms our well-being.

A high concentration of CO2 in the air leads to intoxication of the body and causes a state of hypercapnia. In hypercapnia, a person experiences difficulty breathing, nausea, headache, and may even pass out. If the carbon dioxide content does not decrease, then the turn comes - oxygen starvation. The fact is that both carbon dioxide and oxygen move around the body on the same "transport" - hemoglobin. Normally, they "travel" together, attaching to different places on the hemoglobin molecule. However, an increased concentration of carbon dioxide in the blood reduces the ability of oxygen to bind to hemoglobin. The amount of oxygen in the blood decreases and hypoxia occurs.

Such unhealthy consequences for the body occur when inhaling air with a CO2 content of more than 5,000 ppm (this can be the air in mines, for example). In fairness, in ordinary life we ​​practically do not encounter such air. However, even a much lower concentration of carbon dioxide is not good for health.

According to the findings of some, already 1,000 ppm CO2 causes fatigue and headache in half of the subjects. Many people begin to feel closeness and discomfort even earlier. With a further increase in the concentration of carbon dioxide to 1,500 - 2,500 ppm, the brain is "lazy" to take the initiative, process information and make decisions.

And if the level of 5,000 ppm is almost impossible in everyday life, then 1,000 and even 2,500 ppm can easily be part of the reality of modern man. Ours showed that in sparsely ventilated classrooms, CO2 levels stay above 1,500 ppm most of the time, and sometimes jump above 2,000 ppm. There is every reason to believe that the situation is similar in many offices and even apartments.

Physiologists consider 800 ppm as a safe level of carbon dioxide for human well-being.

Another study found a connection between CO2 levels and oxidative stress: the higher the level of carbon dioxide, the more we suffer from, which destroys the cells of our body.

Carbon dioxide in the earth's atmosphere

In the atmosphere of our planet, there is only about 0.04% CO2 (this is approximately 400 ppm), and more recently it was even less: carbon dioxide crossed the mark of 400 ppm only in the fall of 2016. Scientists attribute the rise in the level of CO2 in the atmosphere to industrialization: in the middle of the 18th century, on the eve of the industrial revolution, it was only about 270 ppm.

Sooner or later, every serious aquarist faces the question of supplying the aquarium with CO2. And for good reason. Why do aquarium plants need it?

So, CO2 - what is it? We all know that they feed primarily on carbon dioxide dissolved in water. This is CO2. In nature, plants get it from the reservoir in which they grow. Since the volume of water in natural reservoirs is very large, its concentration in them is usually constant. But the same cannot be said about aquariums.

Plants quickly use up all the CO2 gas from the aquarium water, and the recovery of its concentration will not occur on its own, because the aquarium is a closed system. Even the fish contained in it will not be able to make up for the lack of CO2, as they exhale such a meager proportion that it will never be enough for plants. And as a result, aquarium plants stop growing.

In addition to the fact that plants stop growing due to a lack of CO2, water in which its content is low has an increased hardness (pH), which is detrimental to them. Even inexperienced aquarists have probably noticed that after adding plants, tap water becomes harder than it was in an empty aquarium. This is due to the fact that it contributes to the appearance of carbonic acid in the water, and it lowers the hardness. That is, it is important to understand: the less CO2 in the water, the higher its pH.

How to help

There are several ways to solve the problem of supplying plants with CO2. You can install a special cylinder and appropriate equipment, or you can go the other way and try to do everything you need with your own hands. Many people prefer this way. And it is clear why - after all, it is much more interesting and pleasant to solve the problem on your own, without resorting to the help of purchased equipment.

The only thing worth paying attention to is the result. Not knowing how everything works in the aquarium, you should not go there and change and redo something, so as not to be upset later. The important thing here is not participation, but understanding what you are doing.

Nowadays, more and more aquarists are engaged in breeding aquatic plants and independently solve problems with a lack of carbon dioxide in the water. To some extent, such a scale may well negate all the results of the fight against harmful emissions from enterprises and cars, because home-made aquarium devices have become necessary and very fashionable, and their volumes are sometimes quite large. Of course, this is a figurative comparison, but there is some truth in these fears.

So, CO2 gas - what is it? How to deal with carbon dioxide in our aquarium and how to produce it inexpensively and in sufficient quantities? But it is quite realistic to make such a system ourselves and refill it 5-7 times a year.

What do aquarium plants need?

Once again, let's recall what CO2 is and why plants need it in an aquarium. CO2 for an aquarium is a source of carbon that plants need, like food for humans. Plants consume it in the light, but in the dark they need oxygen no less. This is the first problem that beginner aquarists face.

If you forget about this, then at night the aquarium will begin to freeze. Even if there is no obvious death of the flora, the plants will simply stop growing normally, and this will make all our efforts meaningless.

In other words, there must always be diffusion (aeration) in the aquarium. And oxygen should be enough for the dark half of the day. Usually there is a lot of it at the beginning of the day, but plants, like fish breathing it, “choose” it pretty quickly. In such a situation, CO2 will not only not be able to help, but will easily exacerbate the problem.

Something else is no less common. Beginners in the aquarium business, seeing how their seemingly unpretentious Vallisneria or easy-to-care Riccia with hygrophila completely refuse to grow, begin to play tricks with CO2 and experiment in the hope of improvement. And the point is not at all an insufficient amount of carbon dioxide or light. These easy-to-keep plants thrive in less light and less carbonated water. It turns out that simply, either the plants were bought “on the verge of death”, or the soil is too poor or the water is new, not yet settled.

What is more important - light, fertilizers or CO2?

Success is simple: CO2 for the aquarium, nutrients and light. And you need to treat it not fictitiously, but with all respect, because all its components are equally important for plant life. If you "disperse" the system in the direction of one of them, without taking into account the other two, then quite quickly and inevitably you will encounter the manifestation of Liebig's law instead of admiring the strong and healthy flora in your artificial pond. This is the so-called swing effect. Moreover, the more the system is overclocked, the more intervention will be required, and in the meantime, the plants "get tired and yearn."

As a result, instead of vigorous greenery in the aquarium, everything gradually fades, and then some of the plantings die altogether. Or the water will begin to fill with algae if the plants cannot “digest” our “broth”.

Factors affecting the composition of water in an aquarium

Interestingly, when thinking about CO2, oxygen, light, and nutrients, temperature is often overlooked. And it is the main regulator of aquarium photosynthesis. Not light and not CO2, as it might seem. Botanists are well aware of this, but "aquarium researchers" forget this fact quite often.

The regulatory role of waves such as infrared reflects precisely this function. Perhaps this is due to the fact that in the technologies used for manufacturing light sources used for aquariums, remembering the temperature is unprofitable. So they pretend it doesn't matter.

What can an aquarium do without?

An aquarium can do without fashionable and glamorous excesses. And not only can, but also safely manages. The main thing is to balance knowledge and cause-and-effect relationships obtained through research in the system. If the system is already in equilibrium, then it no longer needs to be touched! And do not try to fix something that is already working properly.

And yet, if the aquarium tank is too densely planted with plants, then even with good lighting, they may have enough CO2. This is especially true for slightly alkaline hard water. If both species that can absorb only unoccupied carbon dioxide are combined (these are all types of mosses, many grasses that grow only in acidic and soft water, lobelia), and eurion and stenoion species that are able to extract carbon from carbonates (and this is Vallisneria , elodea, echinodorus, etc.), then the concentration of CO2 will be especially low.

It is not at all difficult to cure this, since it is enough just to populate more fish in the aquarium. In those aquariums in which everything is normal with the ecology, and with a dense population of living creatures, plants do not lack carbon dioxide even with fairly powerful light. But in any case, an additional dose of CO2 will not be superfluous for such a reservoir.

We have considered in detail the role of CO2. What it is, now, too, is probably clear. It remains to learn how to make it at home.

The gentle method of supplying the aquarium with carbon dioxide

To enrich the aquarium with carbon dioxide, it is easiest to use ordinary mash. However, she wanders unsteadily. Initially, there will be an excess of gas that will escape, create a greenhouse effect, or create an excess concentration of CO2 in the water. Then the rate of its production will drop sharply.

Disadvantages of the mash method

There are only two of them:

• The need for too frequent recharges (1.5-3 weeks).
• The complexity of monitoring the operation of the system during the day.

However, this does not mean that CO2 supply to the aquarium is not available to you, as these disadvantages are easily solved by using a tank system. True, it has a rather high price, and besides the purchase, it still needs to be professionally configured.

Consider one of the recipes for using such a mash. Its advantage is that fermentation takes place very smoothly and for a long time (3-4 months). Of course, there is nothing new in science, more gas will not come out of the same amount of matter, but the aquarium receives the required amount of CO2 evenly and slowly. For those who need a large amount of carbon dioxide, this recipe will by no means work, they definitely need a CO2 tank. In principle, no mash is suitable for stable high concentrations. But it copes quite satisfactorily with the task of supplying carbon dioxide to an average aquarium with a dense "population", nutrient soil and good illumination, if euryonic and stenoionic species coexist in its hard water.

How to make a CO2 production system for an aquarium with your own hands

We use a polyethylene container with a volume of 1.5 and 2 liters. In each case, the size of the containers may vary, depending on the volume of the aquarium and the amount of carbon dioxide required.

1. Pour the components into the container: 5-6 tablespoons (with a slide) of sugar, one tablespoon of soda and 2-3 tablespoons of starch (also with a slide).

2. Pour 1.5-2 cups of water, as seen in the photo.

3. We send everything to a water bath.

Important: there should be water in the pan almost to the level of the liquid in the bottles, otherwise the composition at the bottom will not become thick, but will remain liquid on top.

4. Cook until the consistency of thick jelly, that is, until ready. You need to get a very thick mixture. If you knock over the bottle, then it should almost not drain.

4. Cool the resulting mixtures.

While the bottles are cooling down, we are engaged in the manufacture of tight and reliable caps with neat pipe fittings. After all, CO2 is a gas, which means that sealing must be very thorough. It is convenient to use fittings for the VAZ brake system (about 12 rubles / pair in auto parts stores). We will need two such fittings, gaskets and washers for 8 (about 40 rubles / a pair of sets in OBI), as well as a pair of nuts for 8.

With a knife and a heated nail, you need to make a hole, then drive the fitting into it with a thread down (thread inside the bottle). Above through the washer, and below according to the scheme: gasket / washer / nut.

It makes no sense to use various adhesives for sealing, since they will not provide the required protection. But the cover made according to the described scheme will securely hold the tube, while the entire CO2 supply system will turn out to be quite resistant to manipulation and recharging.

After the bottles have cooled down, you need to add a teaspoon of yeast (can be dry) to our jelly, before thoroughly mixing them in water. For example, in a glass or a glass.

We put the bottles prepared in this way in place, carefully connect them and do not touch them for 3-4 months. Carbon dioxide is released evenly and slowly, and if low-flow bell-type reactors are used, then the whole process will be easily controlled visually. When the level in the bottles drops below the middle, it's time to recharge them.

Reloading is easy. The fermented mixture turns into a liquid again and pours out, a new one is laid in its place, and you again get CO2 for the aquarium. A do-it-yourself device based on plastic bottles will easily survive many such recharges without losing its qualities. Gas is supplied round the clock.

Types of reactors for aquariums

• "Bell"- this is any reactor made on the principle of an inverted glass. It is not recommended to dissolve the mash with other types of reactors, since the process of carbon dioxide release will become uncontrollable, and the density of CO2 will become uneven.
• The simplest reactor of this type is disposable syringe attached to the wall of the aquarium on a suction cup. Converted bird drinkers also look quite aesthetically pleasing, and besides, they are inexpensive. There are many options: from a plastic cup turned upside down to complex designs.

The efficiency of any reactor directly depends on the "contact spot" - the size of the area of ​​contact between water and gas. Laffart advises for every 100 liters of water (hardness 10 grams) to make a dissolution area of ​​30 square meters. cm. This is not so much - only 5x6 cm.

So, there is a dilemma - to manufacture a large reactor, or a small one, in which the dissolution process will be much better than in a large one.

Such an effect can be obtained by directing part of the water through a thin tube from the filter under the "flute" to obtain a "fountain" inside the reactor. If you organize such a flow, for example, in a reactor from a syringe (20 cubic meters), then the dissolution will improve several times, and the CO2 concentration will be uniform. And this is tantamount to the use of a bell-type reactor, which has more bulky dimensions.

Balloon method of CO2 enrichment

For large aquariums, the optimal method for enriching water with carbon dioxide is the balloon installation method. Such a system consists of a cylinder and a control system, that is, a gearbox, a valve, fittings, a coil with connectors, an air throttle and a power supply. It is not difficult to assemble such an installation yourself, but it is easier to buy a ready-made one in a store, however, it will cost several times more.

Advantages and disadvantages of the balloon method

Advantages:

• Stability of CO2 production.
• Large amount of gas produced.
• Profitability.
• If you connect a pH controller and a CO2 gas analyzer, you can fully automate the process.

Flaws:

• High price.
• The complexity of self-assembly.
• High pressure cylinder required.

Finally

Returning to the choice of CO2 generator, we should also mention another type - chemical. Unlike a mash-powered generator, a chemical one uses the reaction of an acid with carbonates. Like the Braga method, these are suitable for small aquariums - up to 100 liters in size. In addition to everything mentioned in this article, it is possible to purchase a CO2 gas analyzer in the store and use it to constantly monitor the state of the water in your artificial pond.

So let's start with the basics. A person breathes in oxygen and releases carbon dioxide. Carbon dioxide is also released when hydrocarbons are burned. The average level of CO₂ on our planet is currently about 400 PPM (Parts per million - parts per million, or 0.04%) and is constantly growing due to the constant increase in the consumption of petroleum products. At the same time, it is worth knowing that trees absorb carbon dioxide and this is precisely their main function (and not, as it is mistakenly believed that they only produce oxygen).

As long as a person is outdoors, there are no problems, but they begin when he is indoors. If a person is locked in a sealed room without fresh air, then he will die not from a lack of oxygen, as most people mistakenly believe, but from a multiple increase in the level of carbon dioxide that this person himself developed in his lungs. Let's set aside the problems of public transport ventilation (I will write about this separately) and turn our attention to city apartments / country houses, in which there is a massive lack of ventilation.

At the same time, a person spends at least a third of his life in his house / apartment, but in reality half - you can’t save on your own health!

2. The problem of high CO₂ content in the air is especially relevant in the cold season, because In the summer, almost all windows are constantly open. And with the onset of cold weather, the windows are opened less and less, ultimately reducing to episodic ventilation. And, what a coincidence, it is in the cold season that depression, drowsiness and loss of strength appear.

3. Previously, there was even such a tradition - to seal the cracks on the windows before the cold weather. Often, together with window vents, they completely excluded the flow of fresh air into the house. I once again emphasize that fresh air is needed not because it contains the oxygen necessary for breathing, but in order to reduce the excess carbon dioxide content by replacing the air in the room.

4. Many people think that they also have a hood (in apartments, at least in the kitchen and in the bathroom), and the room will be ventilated through it. Yeah, in addition, installing plastic windows that are completely airtight. But how will the air go into the exhaust if you do not have an inflow in the form of either slots in the frames or an open window? And with good traction, it usually pulls air from the entrance.

5. It's worse just to put the air conditioner in the form of a split system and use it with the windows closed. Remember, when the air conditioner is running, DO NOT close the windows! Here is a modern hermetic country house, which has no gaps in the building envelope. And do not be led by stories that wood or aerated concrete "breathe" and therefore you can not give a damn about ventilation. Remember, this term refers to the high vapor permeability of the material, and not the ability to supply fresh outdoor air into the house.

6. Most are limited to a fan on the hood from the bathroom and kitchen. Okay, turn on the fan, all windows and doors are closed in the house. What will be the result? That's right, there will be a rarefaction in the house, because the new air has nowhere to come from. In order for natural ventilation to work, fresh air must enter the house.

7. For measuring the level of carbon dioxide in the air, relatively affordable sensors with an NDIR sensor have now appeared. The non-dispersive infrared method (NDIR) is based on the change in the intensity of infrared radiation before and after absorption in an infrared detector with selective sensitivity. Initially, I was going to buy such a sensor on aliexpress last year (then it cost about $ 100), but the increased price due to the growth of the dollar made me think and look for alternative options. Unexpectedly, this sensor was found in Russia under the Russian brand for the same $ 100 at last year's exchange rate. In total, I found the best offer on Yandex.Market and purchased the sensor at a price of 3,500 rubles. The model is called MT8057. Of course, the sensor has an error, but it is not important when it comes to the fact that measurements with carbon dioxide concentrations exceeding several times the norm are important for us.

8. Closed plastic windows, air conditioners - all this is nonsense compared to the gas stove in the apartment (for the photo, I lit the gas burner, because it had to be washed to shoot the stove).

9. So, all attention is on the chart. The kitchen is 9 square meters, the ceilings are 3 meters high, the door to the kitchen is open (!), the window is closed, there is a hood with a natural impulse (draft is weak in summer), one person. The sensor is placed at a height of 1 meter from the floor, on the dining table. The "normal" level of CO₂ in a room without people is about 600 PPM. One person comes - the level of CO₂ instantly rises. Leaves - falls. Comes again - rises again. And after that it turns on one (!) gas burner. The level of CO₂ almost instantly rises above 2000 PPM. Anxiety! We open the porthole. We observe how the concentration of carbon dioxide in the air slowly decreases. And add 1-2 more people here. Even if you do not turn on the gas stove, then 3 adults without doing hard physical work raise the CO₂ level in the room to a critical level in 30 minutes.

Cooking on a gas stove? Be sure to open the window and turn on the hood (do both at the same time).

Did you turn on the air conditioner? Be sure to open the window.

Are you just in the room? Be sure to open the hatch. And if there are a lot of people in the room, open the window.

And at night, during sleep, the window must be kept open.

In short, you either need to have a supply air duct or a permanently open window.

10. As for trees and how they can be useful. Their most important function during growth is the absorption of carbon dioxide. Few people think about why firewood burns and where there is so much energy in them. So this energy in the form of carbon accumulates in the trunk of a tree as a result of the absorption of carbon dioxide. Trees produce oxygen as a byproduct of photosynthesis.

11. Opening a window in the warm season is not difficult and in general the problem is not so urgent in summer (except when using air conditioners with closed windows). Problems begin in winter, because no one keeps the window open all the time, this is a huge uncontrolled loss of heat and it will be corny cold. It is precisely at this moment that it is worth raising the alarm. Health is priceless.

The problem is very serious and has a global character. For example, until the autumn of last year, I didn’t think at all about the importance of ventilation for health: in an apartment, in a country house. If you look into the past, then it was regular autumn depressions, drowsiness and bad mood during the cold season in a city apartment that prompted you to think in the direction of leaving the city and building, so to speak, because. in autumn-winter I had a headache and there was a general weakness of the body when I was in the city. But as soon as I went out into nature, the problem disappeared. I didn't write it off as a lack of sunlight, but that wasn't the point. In winter, I stopped keeping the window open (it’s cold) and I got a multiple excess of CO₂ in the apartment.

The simplest and most affordable solution to the problem is to keep the window open all the time, or to ventilate, focusing on the readings from the CO₂ sensor. A normal level of CO₂ in a room can be considered a concentration of up to 1000 PPM, if it is higher, it is urgent to ventilate. Humidity can be considered an indirect indicator of the high concentration of carbon dioxide in the air. If, without objective reasons and a decrease in temperature, the humidity in the room begins to rise, it means that the level of CO₂ is increasing.

The danger of an increased concentration of carbon dioxide in the air is that the human body reacts with a very long delay. By the time you felt that it was stuffy in the room and you needed to ventilate it, you had already been in a room with a high content of CO₂ in the air for at least half an hour.

In the next post, I will talk about the problems with ventilation in public transport (buses, trains, planes). I will also show you how to properly organize ventilation in a country house, which for some reason everyone forgets about.

To be continued.

Articles on the topic, for self-study.

(IV) carbon dioxide or carbon dioxide. It is also called carbonic anhydride. It is a colorless, odorless gas with a slightly sour taste. Carbon dioxide is heavier than air and does not dissolve well in water. At temperatures below -78 degrees Celsius, it crystallizes and becomes like snow.

From a gaseous state, this substance passes into a solid state, since it cannot exist in a liquid state under atmospheric pressure conditions. The density of carbon dioxide under normal conditions is 1.97 kg / m3 - 1.5 times higher. Carbon dioxide in solid form is called "dry ice". In a liquid state, in which it can be stored for a long time, it passes with increasing pressure. Let us consider in more detail this substance and its chemical structure.

Carbon dioxide, whose formula is CO2, consists of carbon and oxygen, and it is obtained as a result of the combustion or decay of organic matter. Carbon monoxide is found in the air and underground mineral springs. Humans and animals also release carbon dioxide when they exhale air. Plants without lighting release it, and during photosynthesis intensively absorb it. Thanks to the process of cell metabolism of all living beings, carbon monoxide is one of the main components of the environment.

This gas is not toxic, but if it accumulates in high concentration, suffocation (hypercapnia) may begin, and with its deficiency, the opposite state develops - hypocapnia. Carbon dioxide transmits and reflects infrared. It is which directly affects global warming. This is due to the fact that the level of its content in the atmosphere is constantly growing, which leads to the greenhouse effect.

Carbon dioxide is obtained industrially from smoke or furnace gases, or by the decomposition of dolomite and limestone carbonates. The mixture of these gases is thoroughly washed with a special solution consisting of potassium carbonate. Further, it passes into bicarbonate and decomposes when heated, as a result of which carbon dioxide is released. Carbon dioxide (H2CO3) is formed from carbon dioxide dissolved in water, but in modern conditions it is also obtained by other, more advanced methods. After the carbon dioxide is cleaned, it is compressed, cooled and pumped into cylinders.

In industry, this substance is widely and universally used. Food workers use it as a leavening agent (for example, for making dough) or as a preservative (E290). With the help of carbon dioxide, various tonic drinks and sodas are produced, which are so loved not only by children, but also by adults. Carbon dioxide is used in the manufacture of baking soda, beer, sugar, sparkling wines.

Carbon dioxide is also used in the production of effective fire extinguishers. With the help of carbon dioxide, an active environment is created, which is necessary at a high temperature of the welding arc, carbon dioxide decomposes into oxygen and carbon monoxide. Oxygen interacts with liquid metal and oxidizes it. Carbon dioxide in spray cans is used in air guns and pistols.

Aeromodellers use this substance as fuel for their models. With the help of carbon dioxide, you can significantly increase the yield of crops grown in a greenhouse. It is also widely used in industry in which food is preserved much better. It is used as a refrigerant in refrigerators, freezers, electric generators and other thermal power plants.

Carbon dioxide, carbon monoxide, carbon dioxide are all names for the same substance we know as carbon dioxide. So what are the properties of this gas, and what are its applications?

Carbon dioxide and its physical properties

Carbon dioxide is made up of carbon and oxygen. The formula for carbon dioxide is CO₂. In nature, it is formed during the combustion or decay of organic matter. In the air and mineral springs, the gas content is also quite high. in addition, humans and animals also release carbon dioxide when they exhale.

Rice. 1. Molecule of carbon dioxide.

Carbon dioxide is a completely colorless gas and cannot be seen. It also has no odor. However, with its high concentration, a person may develop hypercapnia, that is, suffocation. Lack of carbon dioxide can also cause health problems. As a result of a lack of this gas, the reverse state of suffocation can develop - hypocapnia.

If carbon dioxide is placed in conditions of low temperature, then at -72 degrees it crystallizes and becomes like snow. Therefore, carbon dioxide in the solid state is called "dry snow".

Rice. 2. Dry snow is carbon dioxide.

Carbon dioxide is 1.5 times denser than air. Its density is 1.98 kg / m³. The chemical bond in the carbon dioxide molecule is covalent polar. It is polar because oxygen has a higher electronegativity value.

An important concept in the study of substances is the molecular and molar mass. The molar mass of carbon dioxide is 44. This number is formed from the sum of the relative atomic masses of the atoms that make up the molecule. The values ​​of relative atomic masses are taken from the table of D.I. Mendeleev and rounded up to whole numbers. Accordingly, the molar mass of CO₂ = 12+2*16.

To calculate the mass fractions of elements in carbon dioxide, it is necessary to follow the formula for calculating the mass fractions of each chemical element in a substance.

n is the number of atoms or molecules.
A r is the relative atomic mass of a chemical element.
Mr is the relative molecular weight of the substance.
Calculate the relative molecular weight of carbon dioxide.

Mr(CO₂) = 14 + 16 * 2 = 44 w(C) = 1 * 12 / 44 = 0.27 or 27% Since carbon dioxide contains two oxygen atoms, n = 2 w(O) = 2 * 16 / 44 = 0.73 or 73%

Answer: w(C) = 0.27 or 27%; w(O) = 0.73 or 73%

Chemical and biological properties of carbon dioxide

Carbon dioxide has acidic properties, as it is an acidic oxide, and when dissolved in water forms carbonic acid:

CO₂+H₂O=H₂CO₃

It reacts with alkalis, resulting in the formation of carbonates and bicarbonates. This gas is non-flammable. Only some active metals, such as magnesium, burn in it.

When heated, carbon dioxide breaks down into carbon monoxide and oxygen:

2CO₃=2CO+O₃.

Like other acidic oxides, this gas easily reacts with other oxides:

СaO+Co₃=CaCO₃.

Carbon dioxide is a constituent of all organic substances. The circulation of this gas in nature is carried out with the help of producers, consumers and decomposers. In the process of life, a person produces about 1 kg of carbon dioxide per day. When we inhale, we get oxygen, but at this moment carbon dioxide is formed in the alveoli. At this point, an exchange occurs: oxygen enters the blood, and carbon dioxide goes out.

Carbon dioxide is produced during the production of alcohol. Also, this gas is a by-product in the production of nitrogen, oxygen and argon. The use of carbon dioxide is necessary in the food industry, where carbon dioxide acts as a preservative, and carbon dioxide in the form of a liquid is contained in fire extinguishers.

Rice. 3. Fire extinguisher.

What have we learned?

Carbon dioxide is a substance that under normal conditions is colorless and odorless. In addition to its common name, carbon dioxide, it is also called carbon monoxide or carbon dioxide.

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