How to mix two liquid substances? For example, some acid and water? It would seem that this problem is from the series “twice two is four.” What could be simpler: drain the two liquids together in some suitable container, and that’s it! Or pour one liquid into a container that already contains another. Alas, this is the same simplicity that, according to an apt popular expression, is worse than theft. Because things can end extremely sadly!
Instructions
There are two containers, one of them contains concentrated sulfuric acid, the other contains water. How to mix them correctly? Should we pour acid into water or, conversely, water into acid? The price of a wrong decision in theory can be a low score, but in practice - at best, a severe burn.
Why? But because concentrated sulfuric acid, firstly, is much denser than water, and secondly, it is extremely hygroscopic. In other words, it actively absorbs water. Thirdly, this absorption is accompanied by the release of a large amount of heat.
If water is poured into a container with concentrated sulfuric acid, the first portions of water will “spread” over the surface of the acid (since water is much less dense), and the acid will begin to greedily absorb it, releasing heat. And there will be so much heat that the water will literally “boil” and splashes will fly in all directions. Naturally, without avoiding the hapless experimenter. Getting burned with “clean” boiling water is not very pleasant, but considering that the water spray will probably still contain acid. The prospect is becoming completely gloomy!
That is why many generations of chemistry teachers forced their students to literally memorize the rule: “First water, then acid! Otherwise, big trouble will happen!” Concentrated sulfuric acid should be added to water in small portions with stirring. Then the unpleasant situation described above will not happen.
A reasonable question: it’s clear with sulfuric acid, but what about other acids? How to properly mix them with water? In what order? It is necessary to know the density of the acid. If it is denser than water, for example, concentrated nitrogen, it should be added to water, just like sulfur, observing the above conditions (little by little, with stirring). Well, if the density of the acid differs very slightly from the density of water, as is the case with acetic acid, it makes no difference.
When concentrated sulfuric acid and water are mixed, a lot of heat is generated. For a chemist, this fact is very important, since both in the laboratory and in industry it is often necessary to prepare dilute solutions of sulfuric acid. To do this, you need to mix concentrated sulfuric acid with water - not always, but often.
How to mix concentrated sulfuric acid and water?
All textbooks and workshops strongly recommend pour sulfuric acid into water (in a thin stream and with good mixing) - and not vice versa: Do not pour water into concentrated sulfuric acid!
Why? Sulfuric acid is heavier than water.
If you pour acid into water in a thin stream, the acid will sink to the bottom. The heat that is released during mixing will dissipate - it will go to heating the entire mass of the solution, since a large amount of water is located above the layer of acid that has sank to the bottom of the vessel.
The heat will dissipate, the solution will heat up - and nothing bad will happen, especially if the liquid is mixed well while adding acid to water.
What will happen if you do wrong , - add water to concentrated sulfuric acid? When the first portions of water fall into the sulfuric acid, they will remain on the surface (since water is lighter than concentrated sulfuric acid). Will stand out a lot of heat that will be used to heat small quantity water.
The water will suddenly boil, resulting in splashes of sulfuric acid and the formation of a caustic aerosol. The effect can be similar to adding water to a hot frying pan with oil. Sulfuric acid splashes can get into your eyes, skin and clothing. Sulfuric acid aerosol is not only very unpleasant to inhale, but also dangerous to the lungs.
If the glass is not heat-resistant, the vessel may crack.
To make this rule easier to remember, they come up with special rhymes like:
“First water, and then acid - otherwise big trouble will happen!”
They also use special phrases for memorization - “memes”, for example:
"Tea with lemon".
Books are good, but I decided to film what the result of incorrectly mixing concentrated sulfuric acid and water looks like in practice.
Of course, with all precautions: from safety glasses to the use of small quantities of substances.
I conducted several experiments - I tried mixing sulfuric acid with water (both correctly and incorrectly). In both cases, only strong heating was observed. But boiling, splashing, and the like did not happen.
As an example, I will describe one of the experiments conducted in a test tube. I took 20 ml of concentrated sulfuric acid and 5 ml of water. Both liquids are at room temperature.
I started adding water to the sulfuric acid. The water boiled only at the moment when the first portions of water were added to the acid. New portions of water extinguished the boil. The caustic aerosol flew (I was not prepared for this, I had to move away for a few seconds). I tried to mix it with an aluminum wire (what I had on hand). Zero effect. I measured the temperature with a thermometer. It turned out to be 80 degrees Celsius. The experiment was hardly a success.
The new experiment was carried out in a flask: so that the contact surface of the two liquids was maximum (this would ensure a sharper release of heat), and the thickness of the water layer above the sulfuric acid was minimal. I did not add water all at once, but in small portions (so that the heat would be used to boil the water, and not to heat the entire mass of water).
So, about 10-15 ml of concentrated sulfuric acid was poured into a conical flask. I used about 10 ml of water.
While I was preparing for the experiment, the acid, under the scorching sun, warmed up to 36-37 degrees (which is 20 degrees higher than the initial temperature of the acid in the previous experiment). The water in the test tube also warmed up slightly, but not so much. I think this played a big role in the success of the experience.
When the main portion of water was added to the sulfuric acid, splashes and a caustic aerosol were noticeably flying. Fortunately, they were carried away by the wind, which was blowing from my side, so I didn’t even feel anything.
As a result, the temperature in the test tube rose above 100 degrees!
What conclusions can be drawn? If you break the rule that Do not add water to concentrated sulfuric acid , splashing does not always occur, but it is possible - especially when the water and acid are warm. Especially if you add water slowly, in small portions and in a wide container.
When working with larger quantities of water and acid, the likelihood of sudden heating and splashing increases (reminder: we only took a few milliliters).
Experience that demonstrates that Do not add water to concentrated sulfuric acid , described in the workshop by the authors Ripan and Ceteanu.
Let me quote:
If you pour water into concentrated sulfuric acid, the first drops of water that fall into it instantly turn into steam and splashes of liquid fly out of the vessel. This occurs because water, having a small specific gravity, is not immersed in the acid, and the acid, due to its low heat capacity, does not absorb the released heat. When hot water is poured in, a stronger splash of sulfuric acid is observed.
Experience.Mixing water with concentrated H 2 SO 4. A glass of concentrated sulfuric acid is placed at the bottom of a large glass covered with a funnel. Warm water is poured in using a pipette (Fig. 161). When hot water is poured in, the inner walls of a large glass and funnel are instantly covered with splashes of liquid.
Rice. 161
In the absence of a glass funnel, you can use a cardboard one, into which a pipette with water is inserted.
If concentrated sulfuric acid is poured dropwise or in a thin stream into a glass of water, you will notice how the heavier sulfuric acid sinks to the bottom of the glass.
When concentrated H 2 SO 4 is mixed with ice, two phenomena can be simultaneously observed: hydration of the acid, accompanied by the release of heat, and melting of ice, accompanied by the absorption of heat. Therefore, as a result of mixing, either an increase or decrease in temperature can be observed. Thus, when mixing 1 kg of ice with 4 kg of acid, the temperature rises to almost 100°, and when mixing 4 kg of ice with 1 kg of acid, the temperature drops to almost -20°.
In the section on the question What happens if acid is poured into water, and vice versa if water is poured into acid asked by the author Profile deleted the best answer is You need to pour sulfuric acid into the water and then everything will be OK.
But if it’s the other way around... then at a minimum it will break the test tube, and at maximum it will hurt you when the acid starts splashing and burning you.
water is lighter than sulfuric acid. The melting point is 10.37 °C with a heat of fusion of 10.5 kJ/mol. It's a lot. - if you pour water into sulfuric acid, the water will boil during the pouring process and begin to splash.
Answer from Deminov Anatoly[guru]
It starts to boil and splash...
Answer from electric welder[guru]
reaction))) but when pouring water into acid, it’s better not to stand close or inhale and don’t stick your eyes in there.... it will sting with feathers
Answer from Neurosis[guru]
Have you heard the expression: acid comes to visit...
Answer from Spica[guru]
a weak solution of acid or water... =))
Answer from Churchill[guru]
The second can only be done in chemical protection overalls.
Answer from Anatoly Podpleletny[guru]
In the first case, the acid is heavier and immediately sinks to the bottom; all you have to do is stir and there will be an electrolyte! And in the second case, light water will begin to splash and burn your eyes if you don’t have glasses!!
Answer from ******
[guru]
Either you will be sighted or vice versa! Water into acid - ABSOLUTELY IMPOSSIBLE! Release in the form of splashes - eyes - face - burns - blindness - loss of beauty - disabled due to stupidity!!
Answer from Mikhail Barmin[guru]
Dissociation (dissolution occurs with the release of a large amount of heat. Do not pour a substance with a higher density into a substance with a lower density, which will lead to better mixing and a lower speed, otherwise the solution will EMISSION and EYE DAMAGE!!
Answer from Ira Yushinova[newbie]
It depends on what kind of acid. In the case of nitric and hydrochloric acids, nothing bad will happen; the acids will simply heat up. The salt one will heat up more. In the case of sulfur, the reaction will proceed with a large release of heat. In the first case, the sulfuric acid will sink to the bottom, so the water has a lower density and the reaction will proceed safely. In the second case, the reaction will take place on the surface with a large release of heat. A similar thing happens when you drop water on a hot frying pan. But eventually the acid will absorb the water.
How to mix two liquid substances? For example, some acid and water? It would seem that this problem is from the series “twice two is four.” What could be simpler: drain the two liquids together in some suitable container, and that’s it! Or pour one liquid into a container that already contains another. Alas, this is the same simplicity that, according to an apt popular expression, is worse than theft. Because things can end extremely sadly!
Instructions
There are two containers, one of them contains concentrated sulfuric acid, the other contains water. How to mix them correctly? Should we pour acid into water or, conversely, water into acid? The price of a wrong decision in theory can be a low score, but in practice - at best, a severe burn.
Why? But because concentrated sulfuric acid, firstly, is much denser than water, and secondly, it is extremely hygroscopic. In other words, it actively absorbs water. Thirdly, this absorption is accompanied by the release of a large amount of heat.
If water is poured into a container with concentrated sulfuric acid, the first portions of water will “spread” over the surface of the acid (since water is much less dense), and the acid will begin to greedily absorb it, releasing heat. And there will be so much heat that the water will literally “boil” and splashes will fly in all directions. Naturally, without avoiding the hapless experimenter. Getting burned with “clean” boiling water is not very pleasant, but considering that the water spray will probably still contain acid. The prospect is becoming completely gloomy!
That is why many generations of chemistry teachers forced their students to literally memorize the rule: “First water, then acid! Otherwise, big trouble will happen!” Concentrated sulfuric acid should be added to water in small portions with stirring. Then the unpleasant situation described above will not happen.
A reasonable question: it’s clear with sulfuric acid, but what about other acids? How to properly mix them with water? In what order? It is necessary to know the density of the acid. If it is denser than water, for example, concentrated nitrogen, it should be added to water, just like sulfur, observing the above conditions (little by little, with stirring). Well, if the density of the acid differs very slightly from the density of water, as is the case with acetic acid, it makes no difference.
Attention, TODAY only!
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