To prepare the solution, it is necessary to mix the calculated amounts of acid of known concentration and distilled water.
Example.
It is necessary to prepare 1 liter of HCL solution with a concentration of 6% wt. from of hydrochloric acid concentration 36% wt.(this solution is used in KM carbonatometers produced by NPP Geosphere LLC)
.
By table 2Determine the molar concentration of an acid with a weight fraction of 6% wt. (1.692 mol/l) and 36% wt. (11.643 mol/l).
Calculate the volume of concentrated acid containing the same amount of HCl (1.692 g-eq.) as in the prepared solution:
1.692 / 11.643 = 0.1453 l.
Therefore, adding 145 ml of acid (36% wt.) to 853 ml of distilled water will obtain a solution of the given weight concentration.
Experiment 5. Preparation of aqueous solutions of hydrochloric acid of a given molar concentration.
To prepare a solution with the required molar concentration (Mp), it is necessary to pour one volume of concentrated acid (V) into the volume (Vв) of distilled water, calculated according to the ratioVв = V(M/Mp – 1)
where M is the molar concentration of the starting acid.
If the acid concentration is not known, determine it by density usingtable 2.
Example.
The weight concentration of the acid used is 36.3% wt. It is necessary to prepare 1 liter of an aqueous solution of HCL with a molar concentration of 2.35 mol/l.
By table 1find by interpolating the values of 12.011 mol/l and 11.643 mol/l the molar concentration of the acid used:
11.643 + (12.011 – 11.643)·(36.3 – 36.0) = 11.753 mol/l
Using the above formula, calculate the volume of water:
Vв = V (11.753 / 2.35 – 1) = 4 V
Taking Vв + V = 1 l, obtain the volume values: Vв = 0.2 l and V = 0.8 l.
Therefore, to prepare a solution with a molar concentration of 2.35 mol/L, you need to pour 200 ml of HCL (36.3% wt.) into 800 ml of distilled water.
Questions and tasks:
What is the concentration of a solution?
What is the normality of a solution?
How many grams of sulfuric acid are contained in the solution if 20 ml are used for neutralization? sodium hydroxide solution whose titer is 0.004614?
Materials and equipment:
Progress:
Iodometric method
Reagents:
1. Potassium iodide is chemically pure, crystalline, and does not contain free iodine.
Examination. Take 0.5 g of potassium iodide, dissolve in 10 ml of distilled water, add 6 ml of buffer mixture and 1 ml of 0.5% starch solution. The reagent should not turn blue.
2. Buffer mixture: pH = 4.6. Mix 102 ml of a molar solution of acetic acid (60 g of 100% acid in 1 liter of water) and 98 ml of a molar solution of sodium acetate (136.1 g of crystalline salt in 1 liter of water) and bring to 1 liter with distilled water, previously boiled.
3. 0.01 N sodium hyposulfite solution.
4. 0.5% starch solution.
5. 0.01 N solution of potassium dichromate. Setting the titer of a 0.01 N hyposulfite solution is carried out as follows: pour 0.5 g of pure potassium iodide into a flask, dissolve it in 2 ml of water, add first 5 ml of hydrochloric acid (1:5), then 10 ml of 0.01 N dichromate solution potassium and 50 ml of distilled water. The released iodine is titrated with sodium hyposulfite in the presence of 1 ml of starch solution, added at the end of the titration. The correction factor to the sodium hyposulfite titer is calculated using the following formula: K = 10/a, where a is the number of milliliters of sodium hyposulfite used for titration.
Analysis progress:
a) add 0.5 g of potassium iodide into a conical flask;
b) add 2 ml of distilled water;
c) stir the contents of the flask until the potassium iodide dissolves;
d) add 10 ml of buffer solution if the alkalinity of the water being tested is not higher than 7 mg/eq. If the alkalinity of the test water is higher than 7 mg/eq, then the number of milliliters of the buffer solution should be 1.5 times greater than the alkalinity of the test water;
e) add 100 ml of test water;
f) titrate with hyposulfite until the solution turns pale yellow;
g) add 1 ml of starch;
h) titrate with hyposulfite until the blue color disappears.
X = 3.55 N K
where H is the number of ml of hyposulfite spent on titration,
K - correction factor to the titer of sodium hyposulfite.
Questions and tasks:
What is the iodometric method?
What is pH?
LPZ No. 6: Determination of chloride ion
Goal of the work:
Materials and equipment: drinking water, litmus paper, ash-free filter, potassium chromate, silver nitrate, titrated sodium chloride solution,
Progress:
Depending on the results of the qualitative determination, 100 cm 3 of the test water or a smaller volume (10-50 cm 3) is selected and adjusted to 100 cm 3 with distilled water. Chlorides are determined at concentrations up to 100 mg/dm 3 without dilution. The pH of the titrated sample should be in the range of 6-10. If the water is cloudy, it is filtered through an ashless filter, washed hot water. If the water has a color value above 30°, the sample is decolorized by adding aluminum hydroxide. To do this, add 6 cm3 of aluminum hydroxide suspension to 200 cm 3 of sample, and the mixture is shaken until the liquid becomes discolored. The sample is then filtered through an ashless filter. The first portions of the filtrate are discarded. A measured volume of water is added to two conical flasks and 1 cm 3 of potassium chromate solution is added. One sample is titrated with a solution of silver nitrate until a faint orange tint appears, the second sample is used as a control sample. If the chloride content is significant, a precipitate of AgCl is formed, which interferes with the determination. In this case, add 2-3 drops of titrated NaCl solution to the titrated first sample until the orange tint disappears, then titrate the second sample, using the first as a control sample.
The following interfere with the determination: orthophosphates in concentrations exceeding 25 mg/dm 3 ; iron in a concentration of more than 10 mg/dm3. Bromides and iodides are determined in concentrations equivalent to Cl - . When normally present in tap water, they do not interfere with determination.
2.5. Processing the results.
where v is the amount of silver nitrate spent on titration, cm 3;
K is the correction factor to the titer of the silver nitrate solution;
g is the amount of chlorine ion corresponding to 1 cm 3 solution of silver nitrate, mg;
V is the sample volume taken for determination, cm3.
Questions and tasks:
Methods for determining chloride ions?
Conductometric method for determining chloride ions?
Argentometry.
Goal of the work:
Materials and equipment:
Experiment 1. Determination of the total hardness of tap water
Measure 50 ml of tap water with a measuring cylinder and pour it into a 250 ml flask, add 5 ml of ammonia buffer solution and an indicator - eriochrome black T - until a pink color appears (a few drops or a few crystals). Fill the burette with 0.04 N EDTA solution (synonyms: Trilon B, Complexon III) to the zero mark.
Titrate the prepared sample slowly with constant stirring with a solution of complexone III until the pink color changes to blue. Record the titration result. Repeat the titration one more time.
If the difference in titration results exceeds 0.1 ml, then titrate the water sample a third time. Determine the average volume of complexone III (V K, CP) consumed for titration of water, and from it calculate the total hardness of the water.
F TOTAL = , (20) where V 1 – volume of analyzed water, ml; V K,SR – average volume of complexone III solution, ml; N K – normal concentration of complexone III solution, mol/l; 1000 – conversion factor mol/l to mmol/l.
Write the results of the experiment in the table:
| V K,SR | N K | V 1 | F GEN |
Example 1. Calculate the hardness of water, knowing that 500 liters contain 202.5 g of Ca(HCO 3) 2.
Solution. 1 liter of water contains 202.5:500 = 0.405 g Ca(HCO 3) 2. The equivalent mass of Ca(HCO 3) 2 is 162:2 = 81 g/mol. Therefore, 0.405 g is 0.405:81 = 0.005 equivalent masses or 5 mmol eq/L.
Example 2. How many grams of CaSO 4 are contained in one cubic meter of water if the hardness due to the presence of this salt is 4 mmol eq
CONTROL QUESTIONS
1. What cations are called hardness ions?
2. What technological indicator of water quality is called hardness?
3. Why can’t hard water be used for steam recovery in thermal and nuclear power plants?
4. Which softening method is called thermal? What chemical reactions occur when water is softened using this method?
5. How is water softened using the sedimentation method? What reagents are used? What reactions take place?
6. Is it possible to soften water using ion exchange?
LPZ No. 8 “Photocolorimetric determination of element content in solution”
Purpose of the work: to study the design and operating principle of the KFK-2 photocolorimeter
PHOTOELECTROCOLORIMETERS. A photoelectric colorimeter is an optical device in which monochromatization of the radiation flux is carried out using light filters. Photoelectric concentration colorimeter KFK – 2.
Purpose and technical data. Single-beam photocolorimeter KFK - 2
designed for measuring transmittance, optical density and concentration of colored solutions, scattering suspensions, emulsions and colloidal solutions in the spectral region of 315–980 nm. The entire spectral range is divided into spectral intervals, separated using light filters. Transmission measurement limits from 100 to 5% (optical density from 0 to 1.3). The basic absolute error of transmittance measurement is no more than 1%. Rice. General form KFK-2. 1 - illuminator; 2 - handle for inserting color filters; 3 - cuvette compartment; 4 - handle for moving cuvettes; 5 - handle (introducing photodetectors into the light flux) “Sensitivity”; 6 - handle for setting the device to 100% transmission; 7 - microammeter. Light filters. In order to isolate rays of certain wavelengths from the entire visible region of the spectrum, selective light absorbers - light filters - are installed in photocolorimeters on the path of light fluxes in front of the absorbing solutions. Operating procedure
1. Turn on the colorimeter 15 minutes before starting measurements. During heating, the cuvette compartment must be open (in this case, the curtain in front of the photodetector blocks the light beam).
2. Enter a working filter.
3. Set the colorimeter sensitivity to minimum. To do this, set the “SENSITIVITY” knob to position “1”, the “SETTING 100 ROUGH” knob to the extreme left position.
4. Set the colorimeter needle to zero using the “ZERO” potentiometer.
5. Place the cuvette with the control solution into the light beam.
6. Close the cuvette compartment lid
7. Using the “SENSITIVITY” and “SETTING 100 ROUGH” and “FINE” knobs, set the microammeter needle to the “100” division of the transmittance scale.
8. By turning the handle of the cuvette chamber, place the cuvette with the test solution into the light stream.
9. Take readings on the colorimeter scale in the appropriate units (T% or D).
10. After finishing work, unplug the colorimeter, clean and wipe dry the cuvette chamber. Determination of the concentration of a substance in a solution using KFK-2. When determining the concentration of a substance in a solution using a calibration graph, the following sequence should be observed:
examine three samples of potassium permanganate solution of different concentrations and record the results in a journal.
Questions and tasks:
Design and principle of operation of KFK - 2
Basic literature for students:
1. Course of basic notes according to the program OP.06 Fundamentals of Analytical Chemistry.-Manual / A.G. Bekmukhamedova - teacher of general professional disciplines ASHT - Branch of the Federal State Budgetary Educational Institution of Higher Professional Education OGAU; 2014
Additional literature for students:
1. Klyukvina E.Yu. Basics of general and inorganic chemistry: tutorial/ E.Yu. Klyukvina, S.G. Bezryadin. - 2nd ed. - Orenburg. Publishing center OSAU, 2011 - 508 pages.
Basic literature for teachers:
1. 1.Klyukvina E.Yu. Fundamentals of general and inorganic chemistry: textbook / E.Yu. Klyukvina, S.G. Bezryadin. - 2nd ed. - Orenburg. Publishing center OSAU, 2011 - 508 pages.
2. Klyukvina E.Yu. Laboratory notebook on analytical chemistry. - Orenburg: OSAU Publishing Center, 2012 - 68 pages
Additional reading for teachers:
1. 1.Klyukvina E.Yu. Fundamentals of general and inorganic chemistry: textbook / E.Yu. Klyukvina, S.G. Bezryadin. - 2nd ed. - Orenburg. Publishing center OSAU, 2011 - 508 pages.
2. Klyukvina E.Yu. Laboratory notebook on analytical chemistry. - Orenburg: OSAU Publishing Center, 2012 - 68 pages
It is what helps digest food. Normally, acid in the stomach is 0.3%.
This is enough to destroy a razor blade. It only takes about a week. The experiments, of course, were carried out outside the human body.
A dangerous object would damage the esophagus and would not stay in the stomach for 7 days.
We will tell you further what other experiments the scientists performed and how they added to the list of properties of hydrochloric acid.
Properties of hydrochloric acid
Hydrochloric acid formula is a mixture of water and hydrogen chloride. Accordingly, the liquid is caustic, which allows it to destroy most substances.
The reagent is colorless in appearance. Its smell gives it away. It is sour, suffocating. The aroma is pungent and, rather, is characterized as a stench.
If hydrochloric acid solution technical, it contains impurities of diatomic and. They give the liquid a yellowish tint.
Unlike, for example, mass of hydrochloric acid in solution cannot exceed 38%.
This critical point, in which the substance simply evaporates. Both hydrogen chloride and water evaporate.
Naturally, the solution smokes. The maximum concentration is indicated for 20-degree air temperature. The higher the degrees, the faster the evaporation occurs.
The density of 38 percent acid is slightly more than 1 gram per cubic centimeter.
That is, even a concentrated substance is very watery. If you drink this liquid, you will get burns.
But you can drink a weak 0.4 percent solution. Naturally, in small quantities. Dilute acid has almost no smell, and its taste is tart and sour.
Reaction of hydrochloric acid with other substances, is largely justified by the monobasic composition of the reagent.
This means that the acid formula contains only one hydrogen atom. This means that the reagent dissociates in water, that is, it dissolves completely.
The remaining substances, as a rule, dissolve in the acid itself. Thus, all metals that stand in front of hydrogen in the periodic table disintegrate in it.
When dissolved in acid, they bind with chlorine. As a result, chlorides are obtained, that is, .
Reaction with hydrochloric acid occurs in most metal oxides and hydroxides, as well as in their .
The main thing is that the latter are obtained from weaker acids. Salt is considered one of the strongest, ranking with chamois.
From gases hydrochloric acid Reacts violently with ammonia. In this case, ammonium chloride is formed. It crystallizes.
The particles are so small and the reaction is so active that the chloride rushes upward. Outwardly it is smoke.
The reaction product with nitrate is also white. This interaction is one of the qualitatively determining salt interactions.
The result of the reaction is a cheesy sediment. This is chloride. Unlike ammonium chloride, it rushes down, not up.
The reaction with nitrate is considered qualitative because it is specific, not characteristic of other one-component acids.
They ignore noble metals, which include argentum. As you remember, it is in the chemical series after hydrogen and, in theory, should not interact with hydrogen chloride dissolved in water.
Hydrochloric acid production
Hydrochloric acid is released not only in laboratory conditions, but also in nature. Human body- part of it.
But, hydrochloric acid in the stomach has already been discussed. However, this is not the only one natural spring, and, in the literal sense.
The reagent is found in some geysers and other water outlets of volcanic origin.
As for hydrogen chloride separately, it is part of bischofite, sylvite, and halite. All these are minerals.
The word “halite” means ordinary salt that is used in food, that is, sodium chloride.
Silvin is a chloride, its shape resembles dice. Bishofite is a chloride, present in abundance in the Volga region.
All of the listed minerals are suitable for industrial production of the reagent.
But, most often they use chloride sodium Hydrochloric acid is obtained when table salt is exposed to concentrated sulfuric acid.
The essence of the method is to dissolve hydrogen chloride gas in water. Two other approaches are based on this.
The first one is synthetic. Hydrogen is burned in chlorine. The second is off-gas, that is, associated.
Hydrogen chloride is used, which is incidentally obtained when working with organic compounds, that is, hydrocarbons.
Absent hydrogen chloride is formed during dehydrochlorination and chlorination of organic matter.
The substance is also synthesized during the pyrolysis of organochlorine waste. Chemists call pyrolysis the decomposition of hydrocarbons under conditions of oxygen deficiency.
Associated raw materials for hydrochloric acid also occur when working with inorganic substances, for example, metal chlorides.
The same sylvite, for example, is used to produce potassium fertilizers. Plants also need magnesium.
Therefore, bischofite does not remain idle. As a result, they produce not only fertilizing, but also hydrochloric acid.
The gas-absorbing method displaces other methods of producing hydrochloric acid. The “by-product” industry accounts for 90% of the reagent produced. Let's find out why it is made and where it is used.
Application of hydrochloric acid
Hydrochloric acid is used by metallurgists. The reagent is needed for pickling metals.
This is the name for the process of removing scale, rust, oxides and just dirt. Accordingly, private craftsmen also use acid when working, for example, with vintage items that contain metal parts.
The reagent will dissolve their surface. There will be no trace left of the problem layer. But, let's return to metallurgy.
In this industry, acid is beginning to be used to extract rare metals from ores.
Old methods are based on the use of their oxides. But, not all of them are easy to process.
Therefore, the oxides began to be converted into chlorides, and then reduced. Now, this is how they get, for example, and.
Since hydrochloric acid is contained in gastric juice, and a low concentration solution can be drunk, it means that the reagent can be used in the food industry.
Did you see the E507 additive on the product packaging? Know that this is hydrochloric acid. It gives that very sourness and tartness to some cakes and sausages.
But most often food emulsifiers are added to fructose, gelatin and citric acid.
E507 is needed not only for taste, but also as an acidity regulator, that is, the Ph of the product.
Hydrochloric acid can be used in medicine. A weak solution of hydrochloric acid is prescribed to patients with low stomach acidity.
It is no less dangerous than increased. In particular, the likelihood of stomach cancer increases.
The body does not receive enough useful elements, even if a person takes vitamins and eats right.
The fact is that for adequate, complete absorption of nutrients, standard acidity is needed.
The last use of the reagent is obvious. Chlorine is obtained from acid. It is enough to evaporate the solution.
Chlorine is used for purification drinking water, fabric bleaching, disinfection, production of plastic compounds, etc.
It turns out that hydrochloric acid, being active and aggressive, is necessary for humanity. There is demand, there is supply. Let's find out the price of the issue.
Hydrochloric acid price
Price product depends on the type. Technical acid is cheaper, purified acid is more expensive. For a liter of the first they ask for 20-40 rubles.
Cost depends on concentration. For a liter of purified reagent they cost about 20 rubles more.
The price tag also depends on the container, packaging, and form of sale. Purchasing acid in plastic canisters of 25-40 liters is more profitable.
In the medical field, in retail, the substance is offered in glass.
For 50 milliliters you will pay 100-160 rubles. This is the most expensive hydrochloric acid.
Buy Hydrogen chloride solution in a liter container is also not cheap. The packaging is designed for private consumers, therefore, they ask for about 400-500 rubles per bottle.
Technical acid is less common in retail and costs about 100 rubles less. The main one is wholesale.
Large enterprises are being purchased. It is for them that the prices indicated at the beginning of the chapter are relevant. The giants do not sell retail.
Accordingly, the cost of the substance in small stores is a reflection of the “appetites” of the store owners.
By the way, about appetite. If the acidity in the stomach is increased, food is digested faster, and you want to eat more often.
This leads to thinness, gastritis and ulcers. People with low acidity are prone to slagging, because food “ferments” in the stomach for a long time and is poorly digested.
This is reflected on the skin, usually in the form of acne and spots. Is there such a problem?
Think not about expensive cosmetics, but about checking your gastrointestinal tract.
Hydrochloric acid is one of the most powerful and dangerous substances for humans on the list of hazardous substances. However, what is surprising is that it exists in the body of every person: hydrochloric acid is an integral part of gastric juice and plays an important role in the digestive process. In an amount of 0.2%, it promotes the transition of food masses from the stomach to the duodenum and neutralizes microbes entering the stomach from external environment. It also activates the enzyme pepsinogen, participates in the formation of secretin and some other hormones that stimulate the activity of the pancreas. For this purpose, it is used in medicine, prescribing its solution to patients to increase the acidity of gastric juice. In general, hydrochloric acid has wide applications in our lives. For example, in heavy industry - for the production of chlorides of various metals, in the textile industry - for the production of synthetic dyes; For the food industry, acetic acid is made from it, and for the pharmaceutical industry, activated carbon is made. It is also a component of various adhesives and hydrolytic alcohol. It is used for etching metals, cleaning various vessels, casing pipes of boreholes from carbonates, oxides and other sediments and contaminants. In metallurgy, hydrochloric acid is used to treat ores, and in the leather industry, leather is used before tanning and dyeing. Hydrochloric acid is transported in glass bottles or rubberized (rubber-coated) metal vessels, as well as in plastic containers.
What is it as a chemical?
Hydrochloric acid, or hydrochloric acid, is an aqueous solution of hydrogen chloride HCl, which is a clear, colorless liquid with a pungent odor of hydrogen chloride. The technical variety of acid has a yellowish-green color due to impurities of chlorine and iron salts. The maximum concentration of hydrochloric acid is about 36% HCl; such a solution has a density of 1.18 g/cm3. Concentrated acid “smoke” in air, since the released gaseous HCl forms tiny droplets of hydrochloric acid with water vapor.
Despite this characteristic, when in contact with air, hydrochloric acid is not flammable or explosive. But at the same time, it is one of the strongest acids and dissolves (with the release of hydrogen and the formation of salts - chlorides) all metals in the voltage series up to hydrogen. Chlorides are also formed when hydrochloric acid reacts with metal oxides and hydroxides. It behaves as a reducing agent with strong oxidizing agents.
Salts of hydrochloric acid are chlorides and, with the exception of AgCl, Hg2Cl2, are highly soluble in water. Materials such as glass, ceramics, porcelain, graphite, and fluoroplastic are resistant to hydrochloric acid.
Hydrochloric acid is obtained from hydrogen chloride in water, which, in turn, is either directly synthesized from hydrogen and chlorine, or obtained by the action of sulfuric acid on sodium chloride.
Industrially produced (technical) hydrochloric acid has a strength of at least 31% HCl (synthetic) and 27.5% HCl (from NaCI). A commercial acid is called concentrated if it contains 24% or more HCl; if the HCl content is less, then the acid is called dilute.
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 when 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.
Hydrochloric acid
Chemical properties
Hydrochloric acid, hydrogen chloride or hydrochloric acid - solution HCl in water. According to Wikipedia, the substance belongs to the group of inorganic strong monobasic compounds. Full name of the compound in Latin: Hydrochloric acid.
Formula of Hydrochloric Acid in chemistry: HCl. In a molecule, hydrogen atoms combine with halogen atoms - Cl. If we consider the electronic configuration of these molecules, we can note that the compounds take part in the formation of molecular orbitals 1s-hydrogen orbitals and both 3s And 3p-atomic orbitals Cl. In the chemical formula of Hydrochloric Acid 1s-, 3s- And 3p-atomic orbitals overlap and form 1, 2, 3 orbitals. Wherein 3s-orbital is not bonding in nature. There is a shift in electron density towards the atom Cl and the polarity of the molecule decreases, but the binding energy of molecular orbitals increases (if we consider it along with other hydrogen halides ).
Physical properties of hydrogen chloride. It is a clear, colorless liquid that has the ability to smoke when exposed to air. Molar mass of chemical compound = 36.6 grams per mole. Under standard conditions, at an air temperature of 20 degrees Celsius, the maximum concentration of the substance is 38% by weight. The density of concentrated hydrochloric acid in this kind of solution is 1.19 g/cm³. In general, physical properties and characteristics such as density, molarity, viscosity, heat capacity, boiling point and pH, strongly depend on the concentration of the solution. These values are discussed in more detail in the density table. For example, the density of Hydrochloric Acid is 10% = 1.048 kg per liter. When solidified, the substance forms crystal hydrates different compositions.
Chemical properties of Hydrochloric Acid. What does Hydrochloric Acid react with? The substance interacts with metals that are in the series of electrochemical potentials in front of hydrogen (iron, magnesium, zinc and others). In this case, salts are formed and gaseous gas is released. H. Lead, copper, gold, silver and other metals to the right of hydrogen do not react with Hydrochloric Acid. The substance reacts with metal oxides, forming water and soluble salt. Sodium hydroxide under the influence of sodium forms water. The neutralization reaction is characteristic of this compound.
Dilute Hydrochloric Acid reacts with metal salts, which are formed by weaker compounds. For example, propionic acid weaker than salt. The substance does not interact with stronger acids. And sodium carbonate will form after reaction with HCl chloride, carbon monoxide and water.
A chemical compound is characterized by reactions with strong oxidizing agents, with manganese dioxide , potassium permanganate : 2KMnO4 + 16HCl = 5Cl2 + 2MnCl2 + 2KCl + 8H2O. The substance reacts with ammonia , this produces thick white smoke, which consists of very small crystals of ammonium chloride. The mineral pyrolusite also reacts with Hydrochloric Acid, since it contains manganese dioxide : MnO2+4HCl=Cl2+MnO2+2H2O(oxidation reaction).
There is a qualitative reaction to hydrochloric acid and its salts. When a substance interacts with silver nitrate a white precipitate appears silver chloride and is formed nitrogen acid . Interaction reaction equation methylamine with hydrogen chloride looks like this: HCl + CH3NH2 = (CH3NH3)Cl.
The substance reacts with a weak base aniline . After aniline is dissolved in water, Hydrochloric Acid is added to the mixture. As a result, the base dissolves and forms aniline hydrochloride (phenylammonium chloride ): (C6H5NH3)Cl. The reaction of aluminum carbide with hydrochloric acid: Al4C3+12HCL=3CH4+4AlCl3. Reaction equation potassium carbonate with it looks like this: K2CO3 + 2HCl = 2KCl + H2O + CO2.
Obtaining hydrochloric acid
To obtain synthetic Hydrochloric Acid, hydrogen is burned in chlorine, and then the resulting hydrogen chloride gas is dissolved in water. It is also common to produce a reagent from exhaust gases, which are formed as by-products during the chlorination of hydrocarbons (exhaust Hydrochloric Acid). In the production of this chemical compound they use GOST 3118 77- for reagents and GOST 857 95– for technical synthetic hydrochloric acid.
In laboratory conditions, you can use an old method in which table salt is exposed to concentrated sulfuric acid. The product can also be obtained using a hydrolysis reaction aluminum chloride or magnesium . During the reaction may form oxychlorides variable composition. To determine the concentration of a substance, standard titers are used, which are produced in sealed ampoules, so that later it is possible to obtain a standard solution of known concentration and use it to determine the quality of another titrant.
The substance has a fairly wide range of applications:
- it is used in hydrometallurgy, pickling and pickling;
- when cleaning metals during tinning and soldering;
- as a reagent for obtaining manganese chloride , zinc, iron and other metals;
- in the preparation of mixtures with surfactants for cleaning metal and ceramic products from infection and dirt (inhibited hydrochloric acid is used);
- as an acidity regulator E507 in the food industry, as part of soda water;
- in medicine with insufficient acidity of gastric juice.
This chemical compound has a high hazard class - 2 (according to GOST 12L.005). When working with acid, special equipment is required. skin and eye protection. A fairly caustic substance that comes into contact with the skin or respiratory tract causes chemical burns. To neutralize it, alkali solutions are used, most often baking soda. Hydrogen chloride vapor forms a caustic mist with water molecules in the air, which irritates the respiratory tract and eyes. If the substance reacts with bleach, potassium permanganate and other oxidizing agents, a toxic gas is formed - chlorine. On the territory of the Russian Federation, the circulation of Hydrochloric Acid with a concentration of more than 15% is limited.
pharmachologic effect
Increases the acidity of gastric juice.
Pharmacodynamics and pharmacokinetics
What is gastric acidity? This is a characteristic of the concentration of Hydrochloric Acid in the stomach. Acidity is expressed in pH. Normally, gastric juice should produce acid and take an active part in the digestive process. Formula hydrochloric acid: HCl. It is produced by parietal cells located in the fundic glands, with the participation H+/K+ ATPases . These cells line the fundus and body of the stomach. The acidity of gastric juice itself is variable and depends on the number of parietal cells and the intensity of the processes of neutralization of the substance by the alkaline components of gastric juice. The concentration of the drug produced is stable and equal to 160 mmol/l. U healthy person Normally, no more than 7 and no less than 5 mmol of the substance should be produced per hour.
With insufficient or excessive production of Hydrochloric Acid, diseases of the digestive tract occur, and the ability to absorb certain microelements, such as iron, deteriorates. The product stimulates the secretion of gastric juice, reduces pH. Activates pepsinogen , converts it into an active enzyme pepsin . The substance has a beneficial effect on the acid reflex of the stomach and slows down the transition of incompletely digested food into the intestines. The fermentation processes of the contents of the digestive tract slow down, pain and belching disappear, and iron is better absorbed.
After oral administration, the drug is partially metabolized by saliva and gastric mucus, the contents of the duodenum. The unbound substance penetrates the duodenum, where it is completely neutralized by its alkaline contents.
Indications for use
The substance is part of synthetic detergents, concentrate for rinsing the mouth and caring for contact lenses. Dilute Hydrochloric Acid is prescribed for stomach diseases accompanied by low acidity, with hypochromic anemia in combination with iron supplements.
Contraindications
The medicine should not be used if allergies on a synthetic substance, for diseases of the digestive tract associated with high acidity, with.
Side effects
Concentrated Hydrochloric Acid can cause severe burns if it comes into contact with the skin, eyes or respiratory tract. As part of various lek. drugs use a diluted substance; with long-term use of large dosages, deterioration of the condition of tooth enamel may occur.
Instructions for use (Method and dosage)
Hydrochloric acid is used in accordance with the instructions.
The medicine is prescribed orally, having previously been dissolved in water. Usually use 10-15 drops of the drug per half glass of liquid. The medicine is taken with meals, 2-4 times a day. The maximum single dosage is 2 ml (about 40 drops). Daily dose – 6 ml (120 drops).
Overdose
Cases of overdose have not been described. With uncontrolled ingestion of the substance in large quantities, ulcers and erosions occur in the digestive tract. You should seek help from a doctor.
Interaction
The substance is often used in combination with pepsin and other medications. drugs. A chemical compound in the digestive tract interacts with bases and certain substances (see chemical properties).
special instructions
When treating with Hydrochloric Acid preparations, you must strictly adhere to the recommendations in the instructions.
Drugs containing (Analogs)
Level 4 ATX code matches:
For industrial purposes, inhibited hydrochloric acid (22-25%) is used. For medical purposes the solution is used: Hydrochloric acid diluted . The substance is also contained in a concentrate for rinsing the mouth. Parontal , in solution for the care of soft contact lenses Biotra .