The percentage concentration of a solution expresses the ratio of the mass of the solute to the mass of the solution as a whole. If we dilute a solution by adding a solvent to it, the mass of the solute will remain unchanged, but the mass of the solution will increase. The ratio of these masses (concentration of the solution) will decrease by as many times as the mass of the solution increases. If we begin to concentrate the solution by evaporating the solvent, the mass of the solution will decrease, but the mass of the solute will remain unchanged. The mass ratio (concentration of the solution) will increase as many times as the mass of the solution decreases. It follows that the mass of the solution and the percentage concentration are inversely proportional to each other, which can be expressed in mathematical form as follows: l. This pattern underlies calculations when diluting and concentrating solutions. Example 1. There is a 90% solution. How much of it should be taken to prepare 500 kg of a 20 percent solution? Solution. According to the relationship between the mass and the percentage concentration of the solution. Hence, it is necessary to take 111 kg of a 90% solution and add enough solvent to it so that the mass of the solution becomes equal to 500 kg. Example 2. There is a 15% solution. To what mass should 8.50 tons of this solution be evaporated to obtain a 60% solution? Solution. If the quantities of solutions are given in volumetric units, they must be transferred to masses. In the future, calculations should be carried out according to the method outlined above. Example 3. There is a 40% solution of sodium hydroxide with a density of 1.43 kg/l. What volume of this solution must be taken to prepare 10 liters of a 15% solution with a density of 1.16 kg/l? Wound" We calculate the mass of a 15% solution: kg n the mass of a 40% solution: Determine the volume of a 40% solution: Example 4. There is 1 liter of a 50% solution of sulfuric acid with a density of 1.399 kg/l. To what volume must this solution be diluted to obtain an 8% solution with a density of 1.055 kg/l? Solution. Find the mass of the 50% solution: kg and the mass of the 8% solution: Calculate the volume of the 8% solution: V - - 8.288 -. = 8 l 288 ml Example 5. 1 l of a 50% nitric acid solution, the density of which is 1.310 g/lm, was diluted with 690 ml of water. Determine the concentration of the resulting solution *. Solution. We find the mass of a 50% solution: your = g and the mass of a dilute solution: We calculate the concentration of a dilute solution: 1 Examples No. 5,6,7 are taken from the book Ya L. Goldfarb, Yu. V. Kho-lakova “Collection of problems and exercises in chemistry.” M., “Enlightenment”, 1968 Example c. There is a 93.6% acid solution with a density of 1.830 g/ml. How much of this solution is required to prepare 1,000 liters of a 20% solution with a density of 1,140 g/ml, and how much water is required for this? Solution. We determine the mass of a 20 percent solution and the mass of a 93.6 percent solution required to prepare a 20 percent solution: We calculate the mass of water required to prepare a dilute solution: We find the volume of a 93.6 percent solution: Example 7. How many milliliters of sulfuric acid with a density of 1 .84 g/ml is required to prepare 1,000 liters of battery acid with a density of 1.18 g/ml) The percentage concentration of the solution and its density are in a certain relationship, recorded in special reference tables. Using them, you can determine the concentration of the solution by its density. According to these tables, sulfuric acid with a density of 1.84 g/ml is 98.72 percent, and with a density of 1.18 g/ml - 24.76-

Currently, the choice of rechargeable batteries is huge - on sale you can find ready-to-use power sources, as well as dry-charged batteries that require preparing the electrolyte and filling it before use. Many people often carry out further battery maintenance at service centers. For various reasons, it may be necessary to prepare the solution yourself. For this event to be successful, you should know how to make electrolyte at home.

Electrolyte is an electrically conductive solution containing distilled water and sulfuric acid, caustic potassium or sodium, depending on the type of power source.

Concentration of sulfuric acid in the battery

This acidity indicator directly depends on the required density of the electrolyte. Initially, the average concentration of this solution in a car battery is about 40%, depending on the temperature and climate in which the power source is used. During operation, the acid concentration drops to 10–20%, which affects the performance of the battery.

At the same time, it is worth understanding that the battery’s sulfur component is the purest liquid, which is 93% composed directly of acid, the remaining 7% being impurities. In Russia, the production of this chemical is strictly regulated - products must comply with GOST requirements.

Differences in electrolytes for different types of batteries

Despite the fact that the principle of operation of the solution is the same for different power sources, you should be aware of some differences in the composition. Depending on the composition, it is customary to distinguish alkaline and acidic electrolytes.

Alkaline batteries

This type of power source is characterized by the presence of nickel hydroxide, barium oxide and graphite. The electrolyte in this type of battery is a 20% solution of caustic potassium. Traditionally, the additive of lithium monohydrate is used, which allows to extend the life of the battery.

Alkaline power sources are characterized by the absence of interaction of the potassium solution with substances formed during battery operation, which helps to minimize consumption.

Acid batteries

This type of power supply is one of the most traditional, which is why the solution in them is familiar to many - a mixture of distilled water and sulfur solution. Electrolyte concentrate for lead-acid batteries is inexpensive and characterized by the ability to conduct large currents. The density of the liquid must correspond to climatic conditions.

Other types of batteries: is it possible to prepare electrolyte for them yourself?

Separately, I would like to draw attention to modern lead-acid power supplies - gel and AGM. They can also be filled with a personally prepared solution, which is in a specific form - in the form of a gel or inside separators. To refill gel batteries, you will need another chemical component - silica gel, which will thicken the acid solution.

Nickel-cadmium and iron-nickel batteries

Unlike lead power supplies, cadmium- and iron-nickel ones are filled with an alkaline solution, which is a mixture of distilled water and caustic potassium or sodium. Lithium hydroxide, which is part of this solution for certain temperature conditions, allows you to increase the service life of the battery.

Table 2. Composition and density of electrolyte for cadmium- and iron-nickel batteries.

How to properly prepare electrolyte at home: safety precautions

Preparing a solution involves working with acids and alkalis, so taking precautions is necessary for the most experienced people. Before you begin, prepare your protective equipment:

• latex gloves
• chemical-resistant clothing and apron;
• protective glasses;
• ammonia, soda ash or boric solution to neutralize acid and alkali.

Equipment

To prepare battery electrolyte, in addition to the power source itself, you will need the following items:

• container and stick, resistant to acids and alkalis;
• distilled water;
• instruments for measuring the level, density and temperature of the solution;
• battery sulfur liquid - for acid batteries, solid or liquid alkalis, lithium - for the corresponding types of batteries, silica gel - for gel batteries.

Process sequence: making an electrolyte for a lead-acid power source

Before starting work, read the information given in Table 3. It will allow you to select the required volume of liquids. The batteries contain from 2.6 to 3.7 liters of acid solution. We recommend diluting approximately 4 liters of electrolyte.

Table 3. Proportions of water and sulfuric acid.

• Pour the required volume of water into a container that is resistant to caustic substances.
• The water should be diluted with acid gradually.
• At the end of the infusion process, measure the density of the resulting electrolyte using a hydrometer.
• Let the composition sit for about 12 hours.

Table 4. Electrolyte density for different climates.

The concentration of the acid solution must be related to the minimum temperature at which the battery is operated. If the liquid is too concentrated, it must be diluted with distilled water.

Watch the video on how to measure the density of an electrolyte.

Attention! You cannot pour water into acid! As a result of this chemical reaction, the composition may boil, which will lead to its splashing and the possibility of acid burns!

Please note that heat is generated during mixing of the components. The cooled solution should be poured into the prepared battery.

Method for diluting electrolyte for an alkaline power source

The density and amount of electrolyte in such batteries is indicated in the operating instructions for the power source or on the manufacturer’s website.

• Pour distilled water into the bowl.
• Add lye.
• Mix the solution, seal it tightly and let it brew for 6 hours.
• After the time has passed, drain the resulting light solution - the electrolyte is ready.

When sediment appears, stir it. If it remains at the end of settling, drain the electrolyte so that the sediment does not get into the battery - this will lead to a decrease in its service life.

Attention! During work, the temperature of the alkaline solution should not exceed 25 degrees Celsius. If the liquid becomes excessively hot, cool it.

After bringing the solution to room temperature and pouring it into the battery, the power source must be fully charged with a current equal to 10% of the battery capacity (60Ah - 6A).

As you can see, preparing an electrolyte solution is not such a difficult matter. The main thing is to clearly determine the required amount of ingredients and remember about safety. Have you tried diluting electrolyte with your own hands? Share your experience with our readers in the comments.

In factory conditions, it is often necessary to dilute concentrated sulfuric acid with water or increase the concentration of diluted acid by adding concentrated acid to it. To do this, you must first establish or check the concentration of ORIGINAL ACIDS by determining the H2SO4 content in THEM.

By adding water to a concentrated acid (oleum or monohydrate), you can get an acid of any concentration, but when mixing it is concentrated. Sulfuric acid and water release a large amount of heat. The acid may heat up to a boil, a violent release of vapors will occur, and the solution may be ejected from the vessel. Therefore, acids are mixed in special apparatus - mixers, taking appropriate precautions.

Mixers for preparing low concentration acid are made of acid-resistant material, and for preparing concentrated acid - from cast iron. Mixers of various designs are used in sulfuric acid. In some cases, the mixer is made of cast iron, enameled on the inside, placed in a steel casing and closed with a lid. The mixed acids enter a cast iron cone enameled on both sides, in which they are mixed, after which they flow into the boiler. To remove the heat generated when mixing acids, a stream of water is continuously supplied into the space between the boiler and the casing, washing the walls of the apparatus.

In some cases, the acid, after mixing in a small tank, enters pipes irrigated with water from outside, where it is simultaneously cooled and further mixed.

When mixing concentrated sulfuric acid with water or more dilute sulfuric acid, it is necessary to calculate the amount of acids mixed. Calculations are carried out according to the so-called rule of the cross. Below are some examples of such calculations.

1. Determine the amount of 100% sulfuric acid and water that must be mixed to obtain 45% II2SO|.

On the left indicate the concentration of a more concentrated acid (in this case 100%), and on the right - a more diluted one (in this case 0% water). Below, between them, indicate the specified concentration (45%). Crossing lines are drawn through the number indicating this concentration, and the corresponding difference in numbers is indicated at their ends:

The numbers obtained using acids of initial concentrations show how many parts by mass of an acid of each of the indicated concentrations must be mixed to obtain an acid of a given concentration. In our example, to prepare 45% acid, you should mix 45 wt. including 100% acid n 55 wt. hours of water.

The same problem can be solved based on the overall balance of II2SO4 (or S03) in sulfuric acid:

0,45.

The numerator on the left side of the equation corresponds to the H2S04 content (in kg) in I kg of 100% sulfuric acid, the denominator corresponds to the total amount of a given solution (in kg). The right side of the equation corresponds to the concentration of sulfuric acid in fractions of unity. Solving the equation, we get x-1.221 kg. This means that 1.221 kg of water must be added to 1 kg of 100% sulfuric acid, resulting in 45% acid.

2. Determine the amount of 20% oleum that should be mixed with 10% nonsulfuric acid to obtain a 98% acid.

The problem is also solved using the cross rule, however, the concentration of oleum in this example must be expressed in % H2SO4 using equations (9) and (8):

A --= 81.63 + 0.1837-20 --= 85.304;

B 1.225-85.304 - 104.5.

According to the rule of the cross

Therefore, to obtain 98% sulfuric acid, it is necessary to mix 88 wt. including 20% ​​oleum and 6.5 wt. including 10% sulfuric acid.

General information. There are furnaces of various designs for firing pyrites: mechanical shelf (multi-hearth), rotating cylindrical, dust-firing furnaces, fluidized-bed furnaces. Pyrite is fired in mechanical shelf kilns...

Amelin A. G., Yashke E. V. As already mentioned, the main part of sulfuric acid is consumed for the manufacture of fertilizers. Plant nutrition especially requires phosphorus and nitrogen. Natural phosphorus compounds (apatites and...

Physico-chemical basis of the process. The process of oxidation of sulfur dioxide to sulfur dioxide proceeds according to the reaction 2S02 + 02^S03 + A^, (45) Where AH is the thermal effect of the reaction. Percentage ratio of the amount of S02 oxidized to S03 to ...

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°.

Approximate solutions. In most cases, the laboratory has to use hydrochloric, sulfuric and nitric acids. Acids are commercially available in the form of concentrated solutions, the percentage of which is determined by their density.

Acids used in the laboratory are technical and pure. Technical acids contain impurities, and therefore are not used in analytical work.

Concentrated hydrochloric acid smokes in air, so you need to work with it in a fume hood. The most concentrated hydrochloric acid has a density of 1.2 g/cm3 and contains 39.11% hydrogen chloride.

The dilution of the acid is carried out according to the calculation described above.

Example. You need to prepare 1 liter of a 5% solution of hydrochloric acid, using a solution with a density of 1.19 g/cm3. From the reference book we find out that a 5% solution has a density of 1.024 g/cm3; therefore, 1 liter of it will weigh 1.024 * 1000 = 1024 g. This amount should contain pure hydrogen chloride:

An acid with a density of 1.19 g/cm3 contains 37.23% HCl (we also find it from the reference book). To find out how much of this acid should be taken, make up the proportion:

or 137.5/1.19 = 115.5 acid with a density of 1.19 g/cm3. Having measured out 116 ml of acid solution, bring its volume to 1 liter.

Sulfuric acid is also diluted. When diluting it, remember that you need to add acid to water, and not vice versa. When diluted, strong heating occurs, and if you add water to the acid, it may splash, which is dangerous, since sulfuric acid causes severe burns. If acid gets on clothes or shoes, you should quickly wash the doused area with plenty of water, and then neutralize the acid with sodium carbonate or ammonia solution. In case of contact with the skin of your hands or face, immediately wash the area with plenty of water.

Particular care is required when handling oleum, which is a sulfuric acid monohydrate saturated with sulfuric anhydride SO3. According to the content of the latter, oleum comes in several concentrations.

It should be remembered that with slight cooling, oleum crystallizes and is in a liquid state only at room temperature. In air, it smokes, releasing SO3, which forms sulfuric acid vapor when interacting with air moisture.

It is very difficult to transfer oleum from large to small containers. This operation should be carried out either under draft or in air, but where the resulting sulfuric acid and SO3 cannot have any harmful effect on people and surrounding objects.

If the oleum has hardened, it should first be heated by placing the container with it in a warm room. When the oleum melts and turns into an oily liquid, it must be taken out into the air and then poured into a smaller container, using the method of squeezing with air (dry) or an inert gas (nitrogen).

When nitric acid is mixed with water, heating also occurs (though not as strong as in the case of sulfuric acid), and therefore precautions must be taken when working with it.

Solid organic acids are used in laboratory practice. Handling them is much simpler and more convenient than liquid ones. In this case, care should only be taken to ensure that the acids are not contaminated with anything foreign. If necessary, solid organic acids are purified by recrystallization (see Chapter 15 “Crystallization”),

Precise solutions. Precise acid solutions They are prepared in the same way as approximate ones, with the only difference that at first they strive to obtain a solution of a slightly higher concentration, so that later it can be diluted precisely, according to calculations. For precise solutions, use only chemically pure preparations.

The required amount of concentrated acids is usually taken by volume calculated based on density.

Example. You need to prepare 0.1 and. H2SO4 solution. This means that 1 liter of solution should contain:

An acid with a density of 1.84 g/cmg contains 95.6% H2SO4 n to prepare 1 liter of 0.1 n. of the solution you need to take the following amount (x) of it (in g):

The corresponding volume of acid will be:

Having measured exactly 2.8 ml of acid from the burette, dilute it to 1 liter in a volumetric flask and then titrate with an alkali solution to establish the normality of the resulting solution. If the solution turns out to be more concentrated), the calculated amount of water is added to it from a burette. For example, during titration it was found that 1 ml of 6.1 N. H2SO4 solution contains not 0.0049 g of H2SO4, but 0.0051 g. To calculate the amount of water needed to prepare exactly 0.1 N. solution, make up the proportion:

Calculation shows that this volume is 1041 ml; the solution needs to be added 1041 - 1000 = 41 ml of water. You should also take into account the amount of solution taken for titration. Let 20 ml be taken, which is 20/1000 = 0.02 of the available volume. Therefore, you need to add not 41 ml of water, but less: 41 - (41*0.02) = = 41 -0.8 = 40.2 ml.

* To measure the acid, use a thoroughly dried burette with a ground stopcock. .

The corrected solution should be checked again for the content of the substance taken for dissolution. Accurate solutions of hydrochloric acid are also prepared using the ion exchange method, based on an accurately calculated sample of sodium chloride. The sample calculated and weighed on an analytical balance is dissolved in distilled or demineralized water, and the resulting solution is passed through a chromatographic column filled with a cation exchanger in the H-form. The solution flowing from the column will contain an equivalent amount of HCl.

As a rule, accurate (or titrated) solutions should be stored in tightly closed flasks. A calcium chloride tube must be inserted into the stopper of the vessel, filled with soda lime or ascarite in the case of an alkali solution, and with calcium chloride or simply cotton wool in the case of an acid.

To check the normality of acids, calcined sodium carbonate Na2COs is often used. However, it is hygroscopic and therefore does not fully satisfy the requirements of analysts. It is much more convenient to use acidic potassium carbonate KHCO3 for these purposes, dried in a desiccator over CaCl2.

When titrating, it is useful to use a “witness”, for the preparation of which one drop of acid (if an alkali is being titrated) or alkali (if an acid is being titrated) and as many drops of an indicator solution as added to the titrated solution are added to distilled or demineralized water.

The preparation of empirical, according to the substance being determined, and standard solutions of acids is carried out by calculation using the formulas given for these and the cases described above.