One of the main properties of living organisms is to maintain acid-base homeostasis at a certain level. Prololitic homeostasis - constancy of pH of biological fluids, fabrics and organs. This is an expression in sufficiently constant pH values \u200b\u200bof biological media (blood, saliva, gastric juice, etc.) and the ability of the body to restore normal pH values \u200b\u200bwhen exposed to protoliths. System supporting protolytic homeostasis,includes not only physiological mechanisms (pulmonary and renal compensation), but also physico-chemical: buffer effect, ion exchange and diffusion.

Buffer solutions called solutions that retain the pH values \u200b\u200bin diluting or adding a small amount of strong acid or base. Protolytic buffer solutions represent mixtures of electrolytes containing the eponymous ions.

Basic proto-censional buffer solutions of two types are distinguished:

Acid Tone consisting of weak acid and an excess of a conjugated base (salt formed by a strong base and an anion of this acid). For example: CH 3 Soam and CH 3 CONA - acetate buffer

CH 3 coam + H 2 O ↔ H 3 O + + CH 3 Soo - excess of conjugate

basis

CH 3 SONA → Na + + CH 3 Coo -

Main, i.e. Consisting weak base and an excess of the acid conjugate with it (that is, the salts formed by the strong acid and the cation of this base). For example: NH 4 OH and NH 4 Cl - ammonia buffer.

NH 3 + H 2 O ↔ OH - + NH 4 + excess

Base

conjugated

NH 4 Cl → Cl - + NH 4 + Acids

The buffer system equation is calculated by the Gasselbach Gasselbach formula:

pH \u003d RK + ℓG, POH \u003d PK + ℓG
,

where RK \u003d -GG to D.

C - molar or equivalent electrolyte concentration (C \u003d V n)

The mechanism of action of buffer solutions

Consider it on the example of acetate buffer: CH 3 Soam + CH 3 CONA

The high concentration of acetate ions is due to the total dissociation of strong electrolyte - sodium acetate, and acetic acid in the presence of the anion of the same name exists in the solution in almost non-ionized form.

With the addition of a small amount of hydrochloric acid, H + ions are associated with a conjugate base of CH 3 available in a solution to weak electrolyte CH 3 coxy.

CH 3 COO ~ + H + ↔ CH 3 COOH (1)

From equation (1) it can be seen that severe NC1 acid is replaced by an equivalent amount of weak acid CH 3 coxy. The amount of CH 3 of the coxy increases, according to the law of dilution of V. ostelald, the degree of dissociation decreases. As a result, the concentration of H + ions in the buffer increases, but very slightly. The pH is continuous.

When adding an acid to the pH buffer is determined by the formula:

pH \u003d RK + ℓG

When a small amount of alkali is added to the briefer, its reaction with CH 3 coxy proceeds. Molecules of acetic acid will react with hydroxide ions with the formation of H 2 O and CH 3 Soo ~:

CH 3 COO + OH ~ ↔ CH 3 COO ~ + H 2 O (2)

As a result, the alkali is replaced by the equivalent number of poorly-home Salt CH 3 Coona. The amount of CH 3 of the Soon decreases, according to the law of dilution of V. ostelald, the degree of dissociation increases due to the potential acidity of the remaining non-exploited molecules of CH 3 of the coxy. Consequently, the concentration of H + ions is practically not changed. PH remains constant.

When adding alkali, the pH is determined by the formula:

pH \u003d RK + ℓG

When diluting the pH buffer also does not change, because The dissociation constant and the ratio of components remain unchanged.

Thus, the buffer pH depends on: dissociation constants and the concentration ratio of components. Than these quantities are more, the greater the pH buffer. The pH buffer will be the largest at the ratio of components equal to one.

For the quantitative characteristics of the buffer introduces the concept buffer tank.

Size: px.

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Transcript.

2 Main issues: 1. Buffer systems, composition and mechanism of their action 2. acetate, phosphate, ammonia, hydrocarbonate, hemoglobine buffers 3. Calculation of pH buffer solutions. 4. Buffer capacity and factors affecting it 5. The value of buffer systems for chemistry and biology, medicine and pharmacy

3 In the process of metabolism in our body, many hydrochloric acids are distinguished, peer-grade, dairy. But Vorunism is strictly retained. The constancy of the pH of biological environments is supported not only with the help of physiological mechanisms (pulmonary and renal compensation), but by the idea of \u200b\u200bphysicochemical buffer, ion exchange and diffusion. Maintaining at a given level of acid-base equilibrium is ensured on molecular strokes.

4 Solutions that retain the constant pH value with the addition of small amounts of strong acids and alkalis, as well as when diluted, are called protolytic buffer systems. The ability of some solutions to maintain the unchanged concentration of hydrogen ions was the name of a buffer action, which is the basic mechanism of theProtolithicomestase. Buffer solutions are a mixture of a weak base or weak acid and their salts. In buffer solutions, according to the theory of Brenstess Loury, the main "acting" components are the formonoakceptorprotons.

5 buffer solutions can be prepared in two ways: 1. Partial neutralization of weak electrolyte with a strong electrolyte: CH 3 coxy (excess) + NaOH; NaOH (excess) + HCl 2. Mixing solutions of weak electrolytes with their salts (or two salts): CH 3 Soam and CH 3 CONA; NH 3 and NH 4 Cl; Nan 2 PO 4 and NA 2 NRA 4

6 The cause of the occurrence of new quality buffer actions in solutions is to combine several protolytic equilibriums in (base) + H + HB + (con. Acid) on (acid) H + + A - (SOPR. Base) Conjugate acid-main pairs of HB + / W / A - are called buffer systems, which are combined equilibrium processionization inhydrolysis.

7 Thus, the protolithic systems consist: of two components. I. Weak conjugate. Acid base II. Weak base is conjugate. Acid one of the components binds H + strong acid, the other is the stronghold.

8 Classification Buffers I. Acid buffer systems. There are a mixture of weak acid on (proton donor) and its salt A - (acceptorPertron). q acetate: CH 3 Soam + CH 3 CONA CH 3 3 SOON Soo Q hydrocarbonate: weak acid conjugate base H 2 with NSO 3 3

9 II. Major buffer systems. There are a mixture of a weak base (proton acceptor) and its salts (donorproton). Ammonium buffer system: a mixture of a weak base of NH 3 H 2 O (proton acceptor) of the salt of a strong electrolyte NH + 4 (proton donor). Buffer Action Zone 8.2-10.2 NH 4 NH OH + 4 Weak Base Conjugate Acid

10 III. Salt Buffers. KN 2 PO 4 + K 2 NRA 4 Intraklets NAH 2 PO 4 + Na 2 HPO 4 Outside Cells The hydrophosphate buffer system (the buffer zone of pH 6.2 8.2). It is a mixture of weak acid H 2 PO - 4 (proton donor) of Jesolinro 2-4 (acceptorPertron) H 2-NRU of weak acid conjugate base

11 IV. Amino acid and protein buffer systems. The buffer effect of these buffer systems begins to appear when it is added to them some amount of acid or alkali. Forming a mumbled: a) a weak "protein acid" + salt of this weak acid b) weak "base" + salt of this weak base

12 The calculation of the pH of the buffer systems (the Equation of the Gende Gasselbach) on the example of acetate buffer solution is considered to be accused to buffersystems. CH SOON CH CONA Sodium acetate almost 3 Full-abandoned: CH 3 CH 3 CHO - + H + 3 Acetic acid dissociates only to a small degree: CH 3 CH 3 co - + H + Apply the law of the active mass of dissociatic acid masses:

13 Prisimation of sodium acetate The equilibrium of acetic acid dissociation is strongly shifted to the left of the intercommunication with the principle of lessel. Almost all the acid in such a solution is introduced by the form of the alignment of its total amount dissociated, forming H + ions and providing an acidic solution of the solution. Therefore, the equilibrium concentration of ill-separated acid in this solution is almost equal to the total concentration, i.e. C (CH 3 coxy) is equal. C (acid). The concentration of acetate ions in the buffer mixture is almost equal to the initial monitoring of the salt: C (CH 3 SO -) C (salt).

14 vioravnization constant of the acetic acid dissociation substitution substitut the overall concentration of the acid of Isoli, we get to d \u003d c with you prologated this equation reminiscent signs for reverse, we obtain: salts, LGC \u003d LGK D C to you, because LG C (H +) \u003d pH, and LGKD \u003d RK acid, then + \u003d k d s with to you salts

15 pH \u003d pk to you LG C with to you salt or pH \u003d pk to you + LG with acid salt This equation is called the gender-garbacha equation. This is the main equation that is used to describe acid-alkaline equilibrium systems.

16 After a similar output for the main buffersystems: POH pH \u003d 14 PK, the main PK + OSR LG with LG C (salt) (base) with C (salt) (base) from the equations it can be seen that the pH of the acidic (main) buffer system depends on The nature of weak electrolyte (RK (acid), RK (base), on the ratio of salt concentrations and acid (base) of the itotmetum.

17 It should be noted that the buffer systems are effectively supported by the Vadiapazone: RK (acids) ± 1 for acid systems; 14 (RK (base) ± 1) for basic systems. The mechanism of action of buffer systems. 1. Devitalization. When diluting the water concentration concentration of Isoli, water is reduced by the same number of times, the wealth of LG C (salt) / s (acid) does not change, therefore the pH of the buffer solution is practically not changed. In addition, the acid ILC of the founding of independence. 2. Adduction of acids. When added to acetate buffer of a small amount of strong acids + (formerized examination)

18 are associated with sazetat-ions contained by vacation, with the formation of weakly dissolving molecules of CH 3 coxy. The degree of dissociation of CH 3 Soone is small and the concentration [H +] is practically not changed, the pH of the buffer solution will decrease, but slightly. CH 3 coon CH 3 Coona + HCl CH 3 COOH + NaCl X x x Buffer pHFl pH \u003d RK to you + LG C with salt to you x + x

19 When adding a small amount of NaOH, OH - ions are neutralized with an acidic component of a buffer solution, a collection of molecularities. CH 3 coon + NaOH CH 3 Coona + H 2 O x x x CH 3 Coona buffer As a result, the added strong base is replaced by an equivalent amount of a weak conjugate base of CH 3, which to a lesser extent affects the reaction of the medium. The pH of the buffer solution increases, but slightly.

20 pH pH \u003d RK to you + LG C with salt to you + x x Example: Compare the change in pH by passing 0.01 mol of chloride through 1 l: acetate buffer p-ra containing 0.1 mol / l salt and acid ; V distilled water The initial zN-EE pH of the buffer p-ra is equal to pH \u003d RKSN 3 coxy \u003d 4.75, because C to you \u003d from salt after adding HCl: pH \u003d 4.75 + lg 0.1 0.01 0.1 + 0.01 pH \u003d 4.66; ΔРН \u003d 4, \u003d 0.09 pH units

21 V pH \u003d 7 for distilled water. After passing 0.01 mol HCl pH \u003d -lg 0.01 \u003d 2; ΔРН \u003d 7 2 \u003d 5 PH units The ability of a buffer solution to maintain pH as a strong acid addition is added or a strong alkali at approximately at the constant level is far uncredited, the values \u200b\u200bof the value of the buffered complex.

22 The buffer capacity buffer capacity (B) is the number of moles of the equivalent of strong acid or alkali, which must be added to 1 lbufer and the pH to the unit. The buffer capacity of the system is determined with respect to the acid added (in oxy.) Or the base (alkali) (in the OSN) and is calculated by Formulas: in acid \u003d C H (HA) pH - pH 0 V (HA), V (B.P.) H in the Osn. \u003d, pH - pH V (b) V (B.P.) where V (HA), V (B) is the volumes of added acids or alkali, etc.; With n \u003d (n), with H (c) molar concentrations of equivalence of acid and alkali, respectively; V (B.R) - the volume of the initial buffer solution, l.; pH o, pH - the pH values \u200b\u200bof the buffer solution to the ipos of the addition of acid or alkali; RN-pH O - DIFFATIVITY MODULAR. C (B) 0

23 buffer tank in relation to kkislot (in acid) is determined by the concentration (number of equivalents) of the component of pine properties; The buffer container in relation to concentration (in the OSN) is determined by the concentration (number of equivalents) with component acid properties in the buffer.

24 buffer capacity depends on the ratio of the components of the concentration of a) the ratio of the components of the acid 90 mmol of 10 mmol \u003d \u003d \u003d mmol HCl + 10 mmol HCl \u003d \u003d LG4 \u003d 0.60 LG0.67 \u003d -0.17 \u003d 0.67 The buffer capacity of the maximum With the ratio of the components of equal unit, with the ox. \u003d ox., Arn \u003d RK

25 b) Concentration of components. The higher the concentration, the more buffer container. Salt acid 20 mmol 50 \u003d 1 \u003d 1 20 mmol mmol HCl + 10 mmol HCl \u003d 0.33 \u003d 0, LG0.33 \u003d 0.48 LG0,67 \u003d -0.17

26 The use of any buffer system is limited to the defined region of pH: for cylinder systemsystem \u003d RK acid ± 1; Forwarding systems pH \u003d 14 - (RK base ± 1). Conclusion: The buffer container mainly depends on the ratio of the concentrations of the components of the absolute concentrations, the acklain, the sores. Blood buffer systems The constancy of the pH of the liquid media is preditted by buffer systems: hydrocarbonate, hemoglobin, phosphate, protein. The effect of all buffer systems in the body is interrelated, which provides a biological fluid-feeding of pH. In the human body and animal, the buffer systems are in the blood (plasma and red blood cells), in cells and intercellular spacesHodrogychkney.

27 Blood buffer systems are represented by plasma buffer systems by Ibuper Erythrocyte systems. Blooming Blood Plasma Buccarbonate Systems 35% protein. 7% Phosphate 2% pH \u003d 7.44% of the role is renimposed. They account for 44% of the buffer blood capacity. Buffer systems of erythrocytes pH \u003d 7.25 hemoglobin 35% hydrocarbonate 18% 56% system of organic phosphates 3% on igidol accounts for 56% buffer blood tank.

The 28 hydrocarbonate-cleaning system The hydrocarbonate buffer system is 53% of the total buffer blood tank (35% in plasma, 18% in red blood cells). Directly measure the concentration of coalic acid in the blood is almost impossible. Therefore, the concentration of carbon dioxide gas is introduced into the Gasselbach equation instead of entering the equation is received.

29 Practically captchas measure the partial pressure of carbon dioxide CO 2. The concentration of the CO 2 dissolved in plasma is calculated, multiplying the solubility constant of CO 2. If it is expressed in kilopascals (kPa), the toxonist is 0.23, if. RT. Art. 0.03. Therefore, if p ω 2 is expressed in the kPa, the equation acquires the following form: pH \u003d 6.1 + Lg Partial pressure CO 2 in the blood plasma is ~ 5.3 kPa (40 mm.rt.st.), which corresponds to the concentration CO 2 ~ 1.2 mmol / l.

30 Partial Pressure CO 2 in the blood plasma is ~ 5.3 kPa (40 mm.rt.st.), which corresponds to a concentration of CO 2 ~ 1.2 mmol / l. The concentration of hydrocarbonate ions in the extracellular fluid at p from 2 \u003d 5.3 kPa is 24 mmol / l. The ratio of extracellular fluid [NSO - 3] / [CO 2] (both values \u200b\u200bin mmol / l) is 20: 1. According to the Gasselbach's genderson equation, this ratio corresponds to the pH of the blood plasma, equal to 7.4: pH \u003d 6.1 + LG24 / 1.2 \u003d 6,1 + LG20 \u003d 6,1 + 1.3 \u003d 7.4 thus active The reaction of the plasma of arterial blood of wealthy people corresponds to pH \u003d 7.40.

31 Since purchase bicarbonates are greater than, the buffer blood system is significantly larger than for acids than for bases. It has great biological significancebecause The accessional of the metabolism of acids is formed more than the foundations. The concentration causes blood alkalinity. Alkaline blood reserve is determined by the volume of carbon dioxide, which is absorbed by 100cm 3 of blood when contacting a fracture mixture containing 5.5% CO 2 at a pressure of 40 mm.T.Sc.Al. The alkaline reserve of blood is 50-65% (volume) from 2.

32 Relatives:< 20 является причиной ацидоза. Различают газовый инегазовый ацидоз. Ацидоз газовый возникает при высокой концентрации СО 2 во вдыхаемом воздухе, заболевании органов дыхания (пневмония), угнетение дыхательного центра (анестетики, седативные препараты). Негазовый ацидоз возникает при накоплении нелетучих продуктов обмена, при ожогах и воспалительных процессах. Повышение соотношения [НСО 3- ]/ [СО 2 ]> 20 crankalkalosis.

33 Alkalosis Gas pneumonia, asthma Consequence of hyperventilation including with intensive ventilation of the lungs (decrease. Conc. CO 2). Alcalosis Negazine Loss of large amounts of HCL with vomiting The elimination of large quantities H + when receiving diuretics Introduction of large amounts of NAHCO 3 long-term reception mineral water with big soda. Alchacy

34 Main clinical manifestations with acidosis and alkalosis acidosis: the oppression of the CNS, at pH below 7, the oppression reaches such an extent to which the orientation is lost; Man falls into a comatose state; Breathing in the aim of removing carbon dioxide as an adaptive alkalosis reaction: the overexcitation of the nervous system, which is accompanied by tetonical (convulsive) abbreviations; may come death from tetonical reduction of respiratory muscles

35 Correction of the acidic base condition of the body. As an emergency assistance in acidosis, intravenous infusion of sodium bicarbonate pages are used, however, when it is administered as a result of neutralization, K-you is allocated from 2, which reduces the effectiveness of the means. This lack of trisamine, binding redundant protons: H 2 N-C (CH 2 OH) 3 + H + H 3 N + -C (CH 2 OH) 3. Lactattniatry is also used as a means of corrective acidosis. To eliminate the phenomena of alkalosis as one of the time measures, rr ascorbic to-you is used.

36 It is possible to change the pH and in other environmental environments, for example, in various digestive tract departments, especially in the stomach. With reduced acidity of the gastric juice, a diluted salt mixture is prescribed with elevated various antacid preparations: Magnesium Magnesium Carbonate MG (OH) 2 4 MgCO 3 H 2 O, Magnesium Oxide, Calcium Carbonate and Calmagin (Granules containing Magnesium Carbonate and Sodium Barbonate) . At the heart of the pharmacological action of all listed funds lies p-inanitralization

37 Hemoglobin buffer system Hemoglobin buffer system is only in red blood cells. The mechanism of its action is associated with the addition and impact of oxygen. In this regard, hemoglobin (HB) has oxidized N. 2 and restored NVV forms. NNV + O 2 NNVO 2 H + + HBO - 2 Acid NNV H + + NV Acid Conjugated base mechanism based on reactions: conjugate base

38 HBO - 2+ H + NNVO 2 NVV + O 2 Base NNVO 2 Acid NVV + H 2 O + HV + H 2 O OH + H 2 ON NV + H + NNV Acid The base from the above schematic reactions shows that the addition of strong acid or A strong alkali causes a protective reaction of the buffer system to preserve the constant pH of the medium, which is explained by the binding to the added H + and it and the formation of lowly subsorative electrolytes.

39 The hemoglobin buffer system of Vortanism effectively functions only in combination with the hydrocarbonate system. 1. Plasma of blood in the blood plasma due to the hydrocarbonate buffer system occurs a number of reactions, as a result of which carbon dioxide is formed. H 2 CO 3 + OH - H 2 O + NSO 3 - NSO 3 + H + H 2 CO 3 CO 2 H 2 O from Blood Plasma CO 2 diffuses into erythrocytes, where the carboanhydraz enzyme catalyzes its interaction with water, fragic acid. 2. Erythrocytes H 2 O + CO 2 H 2 CO 3

40 In the erythrocytes, the concentration of hydrocarbonate ions increases according to the scheme: HB - + H 2 CO 3 NNV + NSO - 3 formed bicarbonate ions diffuse into extracellular liquid. Venous blood returns to the lungs, hemoglobin reacts with oxygen and oxymemoglobin is formed. 3. Light oxymemoglobin reacts with NVV + O 2 NNVO ions 2; NSO 2 + NSO 3- NWO 2- + H 2 CO 3 H 2 CO 3 H 2 O + CO 2 of the lungs CO 2 is removed by a vatmofer due to pulmonary ventilation. This is the principle of maintenance mechanism of acidic acid.

41 Proteined buffer systems Belkone Bucket systems are ampholite, because Their composition includes α amino acids containing groups with acidic properties (Soam and NH + 3) and the main properties (SOO and NH 2). The mechanism of action of such a buffer system can be represented as follows: Acid-clean system A) H 3 N + R COOH + OH H 3 N + R COO + H 2 O Acid protein B) H 3 N + R COO + H + H 3 N + R COO SALE SELL OF ACID (Conjugated base)

42 Main buffer system a) H 2 NR COO + H + H 3 N + R Coo protein base b) H 3 N + R COO + OH H 2 NR COO + H 2 O SOLE SELL OF THE BASE (CONNECTIN ACITED) where R Macromolecular residue squirrel. The role of blood plasma proteins in homeostasis of hydrogen ions is quite small. Phosphate buffer system The phosphate buffer system is contained both in the blood and in cell fluid of other tissues, feature.

43 imaging It is represented by CN 2 PO 4 IR 2 NRA 4, blood pressure and intercellular space - NAH 2 PO 4 and Na 2 HPO 4. The main role in the mechanism of action of this system is Playing H 2 PO - 4: H 2 PO - 4 H + + H 2 PO 2-4 acid sopolls. The basis an increase in the concentration of H + leads to the shift of the reaction to the left, i.e. Both acid: HPO 2-4 H + + H 2 PO - 4 acid con. The base of the phosphate buffer of blood is in close connection with hydrocarbonate. H 2 CO 3 + NRU 2-4 NA NSO 3 + H 2 RO - 4 Skore Schu

44 Ammonium buffer system is formed in glutamine kidneys under the influence of glutamine of oxidative deactivation. NH 3 H + NH + 4 POH \u003d PK + LG NH 4 OH + R COOH R Coonh 4

45 Using the BS in other areas of buffer paintings of soil prevents excessive increase in acidity or cloth, creating and maintaining conditions for the life of plants. Creation of funds-based Observing Common Technological Processing Production Proceedings for the preparation of reference buffer-ditchs, according to the conductivity of the measurement of the measurement. In order to maintain the constancy of the values \u200b\u200bofystemsystem, the BS, dynamics of the flows.

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1. Basic properties exhibits external element oxide: 1) sulfur 2) nitrogen 3) barium 4) carbon 2. Which of the formula corresponds to the expression of the degree of dissociation of electrolytes: 1) α \u003d n \\ n 2) v m \u003d v \\ n 3) n \u003d.

1 Module 1 General Theoretical Basics of Analytical Chemistry. Qualitative analysis Subject: Acid-basic equilibrium and their role in analytical chemistry (in analytics). Buffer systems lecture 5 goal: form

1. Which of the listed elements is the most typical non-metallol? 1) Oxygen 2) sulfur 3) Selenium 4) Tellur 2. Which of the listed items has the greatest electronenence? 1) Sodium

Ministry of Education of the Russian Federation East Siberian State Technological University of Complex test tasks in general and inorganic chemistry Methodical development For independent

1 Lecture 14 ionic reactions Chemical reactions in electrolyte solutions are reduced to the exchange of ions. These reactions are characterized by very high speeds. In the process of reactions of ion exchange degree of oxidation

1 Lecture Lecture Plan: 1. The main provisions of the theory of electrolyte solutions. General (analytical) concentration and activity of ions in solution, their relationship .. Chemical reaction rate and chemical equilibrium.

State institution of higher professional education "Belarusian-Russian University" Department of "Metal Technologies" Chemistry Guidelines to practical training for students

Lecture 3 Lecture Plan: 1. The behavior of strong and weak monosocial acids in aqueous solutions. 2. The behavior of strong and weak single-duty bases in aqueous solutions. 3. The behavior of strong and weak multi-axis

Lecture 14 of the exchange reaction in electrolyte solutions. Working solubility. Dissociation of water. Hydrolysis of salts Basic concepts: ion-exchange reactions, ion-molecular equations, solubility

Solving the tasks of the Olympics "Future of Kuzbass" in Chemistry 1. Perform transformations: MG MGO MGSO 4 Mg (OH) 2 Mg (OH) Cl MgCl 2 Li Li 2 O Lioh Lih 2 PO 4 Li 2 HPO 4 Li 3 PO 4 LA 2 O 3 LA (OH) 2 NO 3 LA (OH) 3

1 Lecture 5 Clinical Pathophysiology Disrupting Acid Basic Condition Content 1. Introduction 2. General information about KSCH 3. The significance of the constancy of KSHC for the body 4. The effects of the pH shift + in that or

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Full-time stage. Grade 11. Solutions. Task 1. A mixture of three gas A, B, with It has a density of hydrogen equal to 14. The portion of this mixture weighing 168 g was passed through an excess of a bromine solution in an inert solvent

The titration curve is a graph of the dependence of the parameter of the system associated with the concentration of the titratable substance, the titrant, or the product of the reaction, on the degree of flow of the titration process (for example, by quantity

Collection of tasks in chemistry for 9 medical class Compiler Ludcheko I.A. Moscow Education Center 109 2012 Mass fraction of a dissolved substance. 1. In 250g solution contains 50g sodium chloride. Determine

Biological fluids, fabrics and organs.

This finds an expression in sufficiently constant pH values \u200b\u200bof biological media (blood, saliva, gastric juice, etc.) and the ability of the body to restore normal values pH when exposed to protoliths. System supporting protolytic homeostasis,includes not only physiological mechanisms (pulmonary and renal compensation), but also physico-chemical: buffer effect, ion exchange and diffusion.

Ensuring the constancy of pH of blood and other organs and tissues is one of the most important conditions for the normal existence of the body. This provision is achieved by the presence of numerous regulatory systems in the body, the most important of which are buffer systems. The latter play a major role in maintaining the core in the body.

In addition, the material of this topic is necessary for studying subsequent topics (potentiometry, properties of Navy solutions, etc.) and such disciplines as biochemistry, microbiology, histology, hygiene, physiology, practical activities Doctor when evaluating the type and severity of corpuscations.

Buffer solutions called solutions that retain the pH values \u200b\u200bin diluting or adding a small amount of strong acid or base. Protolytic buffer solutions represent mixtures of electrolytes containing the eponymous ions.

Basic proto-censional buffer solutions of two types are distinguished:

Acid Tone consisting of weak acid and an excess of a conjugated base (salt formed by a strong base and an anion of this acid). For example: CH 3 Soam and CH 3 CONA - acetate buffer

CH 3 coam + H 2 O ↔ H 3 O + + CH 3 Soo - excess of conjugate

base Acid

CH 3 SONA → Na + + CH 3 Coo -

Main, i.e. Consisting of a weak base and an excess of acid conjugate with it (ie, the salts formed by the strong acid and the cation of this base). For example: NH 4 OH and NH 4 Cl - ammonia buffer.

NH 3 + H 2 O ↔ OH - + NH 4 + excess associated

base of acid

NH 4 Cl → Cl - + NH 4 +

The buffer system equation is calculated by the Gasselbach Gasselbach formula:

pH \u003d RK + LG, POH \u003d PK + LG,

where rk \u003d -lg to D.

C - molar or equivalent electrolyte concentration (C \u003d V n)

The mechanism of action of buffer solutions

Consider it on the example of acetate buffer: CH 3 Soam + CH 3 SONA

The high concentration of acetate ions is due to the total dissociation of strong electrolyte - sodium acetate, and acetic acid in the presence of the anion of the same name exists in the solution in almost non-ionized form.

1. When adding a small amount of hydrochloric acid, H + ions are associated with a conjugate base of CH 3 available in a solution to a weak electrolyte 3 coxy.

CH 3 COO~ + H + ↔ CH 3 COOH (1)

From equation (1) it can be seen that severe NC1 acid is replaced by an equivalent amount of weak acid CH 3 coxy. The amount of CH 3 of the coxy increases, according to the law of dilution of V. ostelald, the degree of dissociation decreases. As a result, the concentration of H + ions in the buffer increases, but very slightly. The pH is continuous.

When adding an acid to the pH buffer is determined by the formula:

pH \u003d RK + LG

2. When a small amount of alkali is added to the briefer, its reaction with CH 3 coxy proceeds. Molecules of acetic acid will react with hydroxide ions with the formation of H 2 O and CH 3 Soo ~:

CH 3 COO + OH ~ ↔ CH 3 COO~ + H 2 O (2)

As a result, the alkali is replaced by the equivalent number of poorly-home Salt CH 3 Coona. The amount of CH 3 of the Soon decreases, according to the law of dilution of V. ostelald, the degree of dissociation increases due to the potential acidity of the remaining non-exploited molecules of CH 3 of the coxy. Consequently, the concentration of H + ions is practically not changed. PH remains constant.

When adding alkali, the pH is determined by the formula:

pH \u003d RK + LG

3. When diluting the pH buffer also does not change, because The dissociation constant and the ratio of components remain unchanged.

Thus, the pH buffer depends on: Disconnection constants and the concentration ratio of components. Than these quantities are more, the greater the pH buffer. The pH buffer will be the largest at the ratio of components equal to one.

For the quantitative characteristics of the buffer introduces the concept buffer tank.

Buffer mechanism (on an example of ammonia buffer)

The mechanism of action of the buffer system Consider on the example of the ammonia buffer system: NN 4 it (NN 3 x H 2 O) + NN 4 C1.

Ammonium hydroxide is a weak electrolyte, in the solution partially dissociates to ions:

NN 4 ON.<=> Nn 4 + + he -

When ammonium chloride hydroxide is added to a solution, salt as a strong electrolyte is almost completely dissociated to ions NN 4 C1\u003e NN 4 + + C1 - and suppresses the dissociation of the base, the equilibrium of which is shifted towards the reverse reaction. Therefore, with (nn 4)? C (base); and with (nn 4 +)? C (salt).

If in the buffer solution with (nn 4) \u003d c (nn 4 С1), then pH \u003d 14 - RKOSN. \u003d 14 + LG 1.8.10-5 \u003d 9.25.

The ability of buffer mixtures to maintain the almost constant pH of the solution is based on the fact that the components that are included in them bind the ions of the H + and ON, injected into the solution or resulting from the reaction flowing in this solution. When an ammonium buffer mixture is added to an ammonium buffer mixture, H + ions will be born with ammonia molecules or ammonium hydroxide, and not to increase the concentration of H + ions and reduce the pH of the solution.

When adding alkali ions, it will bind the ions of NN 4 +, while forming a lowly subsoous compound, and not to increase the pH of the solution.

The buffer action is terminated as soon as one of the components of the buffer solution (conjugate base or conjugate acid) is completely spent.

For the quantitative characterization of the ability of a buffer solution to resist the effect of strong acids and the bases are used, called buffer container. As the concentration of the buffer solution increases, its ability to resist the change in the pH when aciding or alkali is added.

The property of solutions to maintain the pH value under certain limits when the acid is added to small quantities or alkali is called a buffer effect. Solutions with buffer effect are called buffer mixtures.

For the case of titration: Shangic acid and potassium hydroxide, depict the titration curve, specify the titration case, the titration jump, the equivalence point, the indicators used

Titing jump: pH \u003d 4-10. The maximum error in% is less than 0.4.

Indicators - Timolftaleine, phenolphthalene.

Restorener, which elements of the periodic system of elements can be reducing agents and why?

The reducing agent is a substance that changes electrons during the reaction, i.e. Oxisses.

The reducing agents may be neutral atoms, negatively charged non-metal ions, positively charged metal ions in the lowest oxidation, complex ions and molecules containing atoms in the state of an intermediate degree of oxidation.

Neutral atoms. Typical reducing agents are atoms, at the external energy level of which there are from 1 to 3 electrons. This group of recovery includes metals, i.e. S-, D - and F-elements. Recovery properties also show non-metals, such as hydrogen and carbon. In chemical reactions, they give electrons.

Strong reducing agents are atoms with low ionization potential. These include the atoms of the elements of the two first major subgroups of the periodic system of elements D.I. Mendeleev (alkaline and alkaline earth metals), as well as AL, FE, etc.

In the main subgroups of the periodic system, rehabilitation neutral atoms It grows with an increase in the radius of atoms. For example, in a row of Li - FR, a weaker reducing agent will be Li, and strong - FR, which is generally the strongest reducing agent of all elements of the periodic system.

Negatively charged non-metal ions. Negatively charged ions are formed by accession to a neutral atom of non-metal of one or more electrons:

For example, neutral sulfur atoms, iodine, having at external levels 6 and 7 electrons, can attach 2 and 1 electron, respectively and turn into negatively charged ions.

Negatively charged ions are strong reducing agents, as they can give not only weakly retained excess electrons, but also electrons from their external level. At the same time, the more active non-metall as an oxidizing agent, the weaker its rehabilitation in the state of the negative ion. And vice versa, the less active nonmetall as an oxidizing agent, the more active it is in a state of negative ion as a reducing agent.

The reduction capacity of negatively charged ions with the same charge value grows with an increase in the radius of the atom. Therefore, for example, in a group of halogen, Ion iodine has a greater reduction capacity than bromine ions and chlorine, and the fluorine - reducing properties does not show at all.

Positively charged metal ions in the lowest oxidation. Metal ions in the lowest oxidation are formed from neutral atoms as a result of recoils of only parts of electrons from the outer shell. For example, tin atoms, chromium, iron, copper and cerium, entering into interaction with other substances, at first can give the minimum number of electrons.

Metal ions in the lowest oxidation can exhibit replacement properties if they have states with more high degree Oxidation.

In the ORP equation, lay the coefficients by the method of electronic balance. Specify the oxidizer and reducing agent.

K 2 Cr 2 O 7 + 6Feso 4 + 7h 2 SO 4 \u003d K 2 SO 4 + CR 2 (SO 4) 3 + 3Fe 2 (SO 4) 3 + 7H 2 O

1 Cr 2 +6 + 3E x 2 CR 2 +3 Oxidizer

6 Fe +2 - 1e Fe +3 Restore

2kmno 4 + 5h 2 S + 3H 2 SO 4 \u003d K 2 SO 4 + 2mnsO4 + 5S + 8H 2 O

2 Mn +7 + 5e Mn +2 Oxidizer

5 S -2 - 2E S 0 reducing agent

Introduction

Buffer solutions (buffer mixtures, buffers) are solutions containing buffer systems and with the ability to maintain pH at a constant level. They are usually prepared by dissolving in water taken in the corresponding proportions of weak acid and its salt formed by an alkaline metal, partial neutralization of weak acid with a strong alkali or a weak base with a strong acid, dissolving a mixture of polypic acid salts. The pH of the buffer solutions prepared in this way changes with the temperature. The interval of pH values \u200b\u200bin which the buffer solution has resistant buffer properties, lies within the RK ± 1 (RK - negative decimal logarithm Constants of dissociation of weak acid, which is included in its composition). The most famous buffer solutions are: Glycine Salensen, acetate Valpol, phosphate Salensen, Brathant Pale, Veronal Mikhailis, Carbonate Coltguff, Tris-buffer, Universal Veronal Mikhailis, etc.

In laboratory practice, buffer solutions are used to preserve the active reaction of the medium at a certain unchanged level and to determine the hydrogen indicator (pH) - as standard solutions with stable pH values, etc.

Buffer mixes

If you add water to a solution of any acid or alkali, then, of course, the concentration of hydrogen ions or hydroxyl is decreased accordingly. But if you add some amount of water to a mixture of acetic acid and sodium acetate or to a mixture of ammonium hydroxide and ammonium chloride, the concentration of hydrogen ions and hydroxyl in these solutions will not change.

The properties of some solutions remain unchanged the concentration of hydrogen ions during dilution, as well as with the addition of small amounts of strong acids or alkalis is known as a buffer action.

Solutions containing at the same time any weak acid and its salt or any weak base and its salt and the buffer effects are called buffer solutions. Buffer solutions can be considered as mixtures of electrolytes having the ions of the same name. The presence in a solution of weak acid or weak base and their salts reduces the effect of dilution or action of other acids and the base on the pH of the solution.

Such buffer solutions are the following mixtures of CH3 Soam + CH 3 with Oon A, NH 4 OH + NH 4 Cl, Na 2 CO 3 + NaHCO 3, etc.

Buffer solutions that are mixtures of weak acids and their salts, as a rule, have a sour reaction (pH<7). Например, буферная смесь 0,1М раствора СН 3 Coal + 0.1 m SH solution3 with ONA has pH \u003d 4.7.

Buffer solutions that are mixtures of weak base and their salts, as a rule, have an alkaline reaction (pH\u003e 7). For example, the buffer mixture is 0.1 mN 4 OH + 0.1 M Solution N 4 C1 has pH \u003d 9.3.

Acid-major buffer solutions

In a broad sense, buffer names are called systems that support a certain value of any parameter when the composition changes. Buffer solutions can be

- Acid-basic - maintain a constant pH value with the addition of small amounts of acid or base.

Redox - preserve the potential of the system during the introduction of oxidizers or reducing agents.

known metal belts that support the constant pH value.

In all cases, the buffer solution is a conjugate pair. In particular, acid-main buffer solutions contain a conjugate acid-base pair. The buffer effect of these solutions is due to the presence of acid-base equilibrium total type:

On ↔ n + + a -

conjugated acid

Base

B + H + ↔ VN +

ABOUT warm conjugate

Acid

Since this section, only acid-main buffer solutions are considered in this section, we will call them buffer, omitting in the title "Acid-basic".

The buffer solutions call solutions that support the constant pH value when diluted and adding small amounts of acid or base.

Classification of buffer systems

1. Mixtures of solutions of weak acids and their salts. For example, acetate buffer solution.

2. Mixtures of solutions of weak bases and their salts. For example, ammonium buffer solution.

3. Mixtures of solutions of multi-axis acid salts of varying degrees. For example, phosphate buffer solution.

4. Ions and ampholite molecules. These include, for example, amino acids and protein buffer systems. Being in isoelectric state, amino acids and proteins are not buffer. The buffer action is manifested only when some acid or alkali is added to them. At the same time, a mixture of two forms of protein is formed: a) a weak "acid protein" + salt of this weak acid; b) a weak "protein base" + salt of this weak base. Thus, this type of buffer systems can be attributed to the buffer systems of the first or second type.

Calculation of pH buffer solutions

The calculation of the pH of the buffer systems is the law of active masses for acid-base equilibrium. For a buffer system consisting of weak acid and its salts, for example, acetate, ion concentrationH +. It is easy to calculate, based on the equilibrium equilibrium constant:

CH 3 COOH ↔ CH 3 COO - + H +

(1).

From (1) it follows that the concentration of hydrogen ions is equal to

(2)

In the presence of CH 3 Coona Acid-basic equilibrium of acetic acid is shifted to the left. Therefore, the concentration of the unfinished acetic acid is virtually equal to the concentration of acid, i.e. [SN3 COOH] \u003d S acid

The main source of acetate ions is a strong electrolyteCH 3 Coona:

CH 3 COONA → Na + + CH 3 Coo -,

Therefore, you can accept that [CH 3 COO -] \u003d Salt . Taking into account the assumptions made, equation (2) takes the form:

From here, the Equation of Genderson-Hasselbach is obtained for buffer systems consisting of weak acid and its salt:

(3)

For a buffer system consisting of a weak base and its salt, for example, ammonia, the concentration of hydrogen ions in solution can be calculated based on the dissociation constant of a weak base.

NH 3 × H 2 O \u003d NH 4 OH ↔ NH 4 + + OH -

(4)

Express the concentration of ionsOh - from ionic water

(5)

and we substitute in (4).

(6)

From (6) it follows that the concentration of hydrogen ions is equal to

(7)

In the presence of NH 4 Cl Acid-basic equilibrium shifted to the left. Therefore, the concentration of the unseen ammonia is almost equal to the concentration of ammonia, i.e. [NH 4 Oh] \u003d from the OSN.

Main source of ammonium cations - strong electrolyteNH 4 Cl:

NH 4 Cl → NH 4 + + Cl -,

Therefore, you can accept that [NH 4 +] \u003d from salt . Taking into account the assumptions made, equation (7) takes the form:

(8)

Hence the Equation of Genderson-Hasselbach is obtained for buffer systems consisting of a weak base and its salt:

(9)

In a similar way, it is possible to calculate the pH of the buffer system consisting of a mixture of solutions of poly-axial acids of various degrees of substitution, for example, phosphate, consisting of a mixture of hydrophosphate solutions (Na 2 HPO 4 ) and dihydrophosphate (NAH 2 PO 4 ) Sodium. The basis of its action lies with an acid-base equilibrium:

H 2 PO 4 - ↔ H + + HPO 4 2-

Weak Acid Conjugated Base

(10)

Expressing hydrogen ions concentration from (10) and making the following assumptions:

[H 2 PO 4 -] \u003d C (H 2 PO 4 -); [HPO 4 2-] \u003d C (HPO 4 2-), we get:

(11).

Progrifting this expression and changing signs to the opposite, we obtain the Equation of Genderson-Hasselbach to calculate the pH of the phosphate buffer system

(12),

Where RK B (H 2 PO 4 - ) - Negative decimal logarithm constant dissociation

phosphoric acid at the second stage; from (H 2 PO 4 -) and C (HPO 4 2- ), respectively, the concentration of acid and salt.

Properties of buffer solutions

The pH value of buffer solutions remains unchanged when diluted, which follows from the Holderson Hasselbach equation. When diluting the buffer solution with water, the concentration of both components of the mixture decreases to the same number of times. Consequently, the pH value should not change. However, experience shows that some change in pH, although insignificant, still happens. This is explained by the fact that the Hasnel Khasselbach equation is approximate and does not take into account the modes. With accurate calculations, a change in the coefficients of the activity of conjugate acids and bases should be considered.

Buffer solutions change little pH when adding small amounts of acid or base. The ability of buffer solutions to maintain the constancy of the pH when small amounts of severe acid or a strong base are added to them, it is based on the fact that one component of the buffer solution can interact with H+ acid accusable, and the other with OH- Added base. As a result, the buffer system can bind asH + and OH - And to a certain limit to maintain the constancy of the pH. We will demonstrate this by an example of a formative buffer system, which is a conjugate acid-base pairHCOOH / HCOO - . Equilibrium in a solution of a formative buffer solution can be represented by the equation:

HCOOH ↔ HCOO - + H +

When adding a strong acid, the conjugate baseHCOO - Binds added ionsH +. , turning into a weak formic acid:

HCOO - + H + ↔ HCOOH

In accordance with the principle of Le Chatelier, the balance is shifted to the left.

When adding alkali protons of formic acid bind added ions- in water molecules:

HCOOH + it - → HCOO - + H 2 O

Acid-basic equilibrium according to Le Chatelle is shifted to the right.

In both cases, small changes occur in the ratioHCOOH / HCOO - But the logarithm of this ratio changes little. Consequently, the pH of the solution changes slightly.

Essence of buffer action

The effect of buffer solutions is based on the fact that the individual components of buffer mixtures bind hydrogen ions or hydroxyl acids injected into them and the formation with the formation of weak electrolytes. For example, if to a buffer solution containing weak acid onn. and this acid saltKT A N. , add alkali, then the reaction of the formation of weak electrolyte water will occur:

N + + he → n 2 o

Therefore, if the buffer solution containing the acid, add alkali, the hydrogen ions formed during the electrolytic acid dissociation onn. , binds to the ions of hydroxyl added alkali, forming weak electrolyte-water. Instead of consumed hydrogen ions, due to the subsequent acid dissociation onn. , new hydrogen ions appear. As a result, the former concentration of+ - ions in the buffer solution will be restored to the initial value.

If a strong acid is added to the specified buffer mixture, then the reaction will occur:

H + + A N - → on N

those. A n - - ions formed in the electrolytic dissociation of salt tot a N. , connecting with hydrogen ions of added acid, form molecules of weak acid. Therefore, the concentration of hydrogen ions from the added severe acid to the buffer mixture will not change. Similarly, you can explain the effect of other buffer mixtures.

PH value in buffer solutions

Changing relationships and you can get buffer

solutions that differ in smooth change in pH from them are minimally possible values. In aqueous solution of weak acid

[N +] \u003d √k Han * c Han

from

pH \u003d - LG [H +] \u003d - - LG K HAN - - LG C HAN

But since K Han represents a constant value, then its best to present in the formpK Han. those. Indicator Constant Electrolytic Dissociation:pK Han \u003d - LG K HAN.

Then we get that in aqueous solution of weak acid:

pH \u003d - LG [H +] \u003d - - PK HAN - - PC HAN

As it adds to an aqueous solution of weak acid, its pH solo solution will change.

According to the equation, in a solution containing a mixture of weak acid and its salt [+] \u003d K Han

that

pH \u003d - lg [n +] \u003d - lg k han - lg c han + lg c kt a n.

Similarly, we derive the formula in relation to weak grounds:

[He] \u003d √k KTOH * C KTOH

pOH \u003d - LG [ON] \u003d - - LG K KTOH - - LG C KTOH

The concentration of hydrogen ions is also expressed by the following formula [+] \u003d so

pH \u003d PK W - (- PK KTOH - - LG C KTOH)

According to the equation, in a solution containing a mixture of a weak base and its salt

[H +] \u003d

t. e.

pH \u003d - LG [H +] \u003d - LG K W + LG K KTOH - LGC KT A n + LG C KTOH.

There is no need to memorize the pH values \u200b\u200bderived by the formula, since they are very easily derived by logarithming simple formulas expressing the value [H+ ].

Buffer capacity

The ability of buffer solutions to maintain the constancy of the pH value is not limited and depends on the qualitative composition of the buffer solution and the concentration of its components. When significant quantities of severe acid or alkalis are observed to the buffer solution, a noticeable change in pH is observed. Moreover, for various buffer mixtures, differing from each other in composition, differing from each other in composition, the buffer action is not the same. Therefore, the buffer mixtures can be distinguished by the strength of the resistance rendered to the action of acids and alkalis administered to the buffer solution in the same quantities and a certain concentration. The limit amount of acid or alkali of a certain concentration (in mol / l or g - eq / l), which can be added to the buffer solution so that the pH value changes only by one unit, is called buffer container.

If the value [H + ] one buffer solution varies with added strong acid less than the value [n+ ] Another buffer solution when adding the same amount of acid, the first mixture has a greater buffer capacity. For the same buffer solution, the buffer container is the greater the higher the concentration of its components.

Buffer properties of solutions of strong acids and bases.

Solutions of strong acids and bases at a sufficiently high concentration also possess a buffer effect. Conjugate systems in this case are3 O +/N 2 O - for strong acids and he- / n 2 O - for severe grounds. Strong acids and bases are completely dissociated in aqueous solutions and therefore are characterized by a high concentration of hydroxony ions or hydroxyl - ions. Adding small amounts of severe acid or a strong base to their solutions, therefore it has only a minor effect on the pH of the solution.

Preparation of buffer solutions

1. Dilution in the measuring flask of the corresponding fixanals.

2. The quantity of suitable conjugate acid-base steam calculated by the gender-hasselbach equation is mixed.

3. Partial neutralization of weak acid with a strong alkali or a weak base with a strong acid.

Since the buffer properties are very weak, if the concentration of one component is 10 times and more different from the concentration of the other, the buffer solutions are often prepared by mixing the solutions of the concentration of both components or adding to a solution of one component of the corresponding amount of reagent leading to the formation of an equal concentration of the conjugate form. In reference books, there are detailed recipes for the preparation of buffer solutions for different pH values.

The use of buffer solutions in chemical analysis

The buffer solutions are widely used in chemical analysis in cases where, under the experimental conditions, the chemical reaction must proceed under the accurate pH value that does not change when diluting the solution or when other reagents are added to it. For example, when carrying out the reaction of the reduction oxidation, during the deposition of sulphides, hydroxides, carbonates, chromates, phosphates, etc.

Here are some cases of use for analysis purposes:

Acetate buffer solution (snzons + sn3 Soo Na. ; pH \u003d 5) is used in precipitation of precipitation simplified in acidic or alkaline solutions. Harmful influence of acids suppresses sodium acetate, which reacts with severe acid. For example:

NS1 + CH 3 Soo N A → CH 3 Soam + Na C1

or in ion form

H + + CH 3 Soo → CH 3 Soam.

Ammonary -ammonium buffer solution (N H 4 OH + N H 4 C1; pH \u003d 9) is used in precipitation of barium carbonates, strontium, calcium and separating them from magnesium ions; in the deposition of nickel sulphides, cobalt, zinc, manganese, iron; as well as during the excavation of aluminum, chromium hydroxides, chromium, beryllium, titanium, zirconium, iron, etc.

Formant buffer solution (NSON + NSOON. but; pH \u003d 2) are used when separating zinc ions deposited asZNS. In the presence of cobalt, nickel, manganese, iron, aluminum and chromium.

Phosphate buffer solution (N A 2 NRO 4 + N AN 2 RO; pH \u003d 8) uses when carrying out many reactions of reduction oxidation.

For successful application Buffer mixtures for analysis it is necessary to remember that not every buffer mixture is suitable for analysis. The buffer mixture is chosen depending on its purpose. It should satisfy a certain quality composition, and its components must be present in the solution in certain amounts, since the effect of buffer mixtures depends on the relation of the concentration of their components.

The above can be represented as a table.

Buffer solutions used in the analysis

Buffer mixture	Composition of the mix (with a molar ratio of 1: 1)	pH
Formative	Formic acid and sodium formate
Benzoyatnaya	Benzoic acid and ammonium benzoate
Acetate	Acetic acid and sodium acetate
Phosphate	Oncestable and dual-sufficient sodium phosphate
Ammonium	Ammonium hydroxide and ammonium chloride

Buffer action also have mixtures of acid salts with different substitution of hydrogen with metal. For example, in a buffer mixture of dihydrophosphate and sodium hydrophosphate, the first salt plays the role of weak acid, and the second role of its salt.

Variating the concentration of weak acid and its salt, it is possible to obtain buffer solutions with specified pH values.

In animals and plant organisms there are also complex buffer systems that support the pH of blood, lymphs and other liquids. The buffer properties also have a soil to oppose external factors changing the pH of the soil solution, for example, when an acid or base is introduced into the soil.

Conclusion

So, buffer solutions call solutions supportinga constant pH value when diluting and adding small amounts of acid or base. An important property of buffer solutions is their ability to maintain a constant pH value when the solution is diluted. Solutions of acids and bases can not be called buffer solutions, because When diluting their water pH solution changes. The most effective buffer solutions are prepared from solutions of weak acid and its salt or a weak base and its salt.

Buffer solutions can be considered as mixtures of electrolytes having the ions of the same name. Buffer solutions play important role In many technological processes. They are used, for example, with electrochemical application of protective coatings, in the production of dyes, skin, photographic materials. Widely used buffer solutions in chemical analysis and for calibrating pH-meters.

Many biological fluids are buffer solutions. For example, pH of blood in the human body is maintained in the range from 7.35 to 7.45; gastric juice from 1.6 to 1.8; saliva from 6.35 to 6.85. Components of such solutions are carbonates, phosphates and proteins. In bacteriological studies in the cultivation of bacteria, the buffer solutions also have to use.

Bibliographic list

1. Kreszkov A.P. Basics of analytical chemistry. KN.1. - M: Chemistry, 1965. -498 p.

2. Citovich I.K. Course of Analytical Chemistry: Textbook for universities. - St. Petersburg: "Lan", 2007.- 496 p.

3. Kreshkov A.P., Yaroslavtsev A.A. Course of analytical chemistry. KN.1. Qualitative analysis. - 2rd ed. Perverted. - M.: Chemistry, 1964 - 432 p.

4. Chemistry: Handbook for high school students and arriving in universities / ed. Lydia R.A., Alikbarova L.Yu. - M.: AST-PRESS School, 2007. -512С.

5. Osipov Yu.S., Large Russian Encyclopedia: In 30 t. T.4.- M.: Large Russian Encyclopedia 2006 - 751 p.

6. Mikhaylenko Ya.I., Introduction to Chemical Analysis, Goshimtekhizdat, 1933.