Buffer decisions and powers. Buffer solution is a chemical reagent with a constant pH. Stuck buffer connections
The student is guilty of:
1. Rosrahovuvati pH buffering systems.
2. Rosrahovuvati buffer
The pH value does not change due to the addition of small amounts of strong acids and meadows, as well as the dilution, to name
buffers.
Most often, in the capacity of buffer solutions, there is a mixture of weak acids and salts, as well as a combination of weak bases and salts, or, nareshty, total solutions of salts of polybasic acids of a single step.
For example: UNLO
formate, pH = 3.8
CH3 COOH
acetate, pH = 4.7
CH3 COONa
NaH2 PO4
phosphate, pH = 6.6
Na2 HPO4
NH4 OH |
amichana, pH = 9.25 |
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NH4 CI |
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The mechanism of the buffer systems is easy to understand: |
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1. When acid is added to the |
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weak acid: |
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CH3 COOH |
CH3 COOH |
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CH3 COONa |
CH3 COOH |
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2. When given in advance, the hydroxide ion is called into |
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weak electrolyte (H2O): |
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CH3 COOH |
CH3 COONa |
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CH3 COONa |
CH3 COONa |
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Relief of weak electrolytes when acid is added to the buffer solution and, if necessary, the pH value is increased.
Calculation of the pH of buffer solutions
1. Buffer decisions, approved |
pH = pKic acid - |
3 acids |
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weak sour і її silly |
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Z soli |
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pK - strength indicator of acid: |
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рК = - lg Ккіслоти |
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2. Buffer decisions, approved |
pOH = pKosnov. |
Z p_davi |
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weak food and salts. |
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Z soli |
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I know, scho pH + pOH = 14, zvidsy |
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pH = 14 - p |
Z p_davi |
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Z soli |
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Health of buffer systems buffer mnistyu. Take a small amount of moles equivalent to a strong acid and a strong base, as it is necessary to add up to 1 liter
buffer system and range, change pH per unit.
The size of the buffer sum is carried out according to the formulas:
de B - buffer Umenity;
CA, SV - concentration of speech buffer sums.
Buffer The group is larger than the concentration of the components in the sum. It would be efficient to achieve the buffer sum, so that the buffer was not changed much,
The concentration of one component is not to blame for the concentration of the other component more than 10 times less.
Apply RISHENNYA TYPOVIKH ZAVDAN
Calculation of the pH of the buffer solutions,
weak sour і її silly
Appendix 1. Calculate the pH of the sum of 0.03 n the range of oztic acid CH 3 COOH s
0.1 n range of CH3 COONa, and the strength index of acid is pK = 4.8.
pK (CH3 COOH) = 4.8 C (f (CH3 COOH) =
0.03 mol / L C (f (CH3 COONa) =
So yak M (f) = M for CH3 COOH і for CH3 COONa, then for cich speech C = C (f)
pH рКкіcl. - lg sour. Ssolі
pH 4.8 - lg 0.03 4.8 lg 0.3 4.8 - (-0.52) 5.32 0.1
Type: pH = 5.32
Appendix 2. Calculate the pH of the range, cut off with a path of 20 ml
0.05 m range of nitric acid HNO2 і 30 ml 1.5 m range of sodium nitrite
NaNO2.
V (HNO2) = 20 ml |
1. We know about the size of the message |
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З (HNO2) = 0.05 mol / l |
acids HNO2 і salts NaNO2 і їх concentration |
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V (HNO2) = 30 ml |
in otrimanіy sumіshі: |
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З (HNO2) = 1.5 mol / l |
V = 20 + 30 = 50 ml |
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Z (HNO 2) |
0.02 mol / l |
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2. According to the tables, it is known that pK HNO 2 = 3,29.
3. Quantifiable pH:
C (NaNO2) 1.5 30 0.9 mol / L Type: pH = 4.94 50
Appendix 3. Slices of 0.5 m to the size of sodium acetate CH3 COONa, it is necessary to add up to 100 ml to the size of 2 m of scintillate acid CH 3 COOH, trim the buffer solution with pH = 4?
C (CH3 COONa) = 0.5 mol / l |
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Z soli |
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3 acid |
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Z soli |
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From the same, the ratio of the concentration of acid to the concentration of salt
maє dorivnuvati 5.754: 1.
2. The known concentration of acid in the buffer system:
4. It is known the amount of 0.5 m to the size of sodium acetate CH3 COONa,
Appendix 4. In some molar spiws, it was necessary to take the range of salts to the store NaH2 PO4 and Na2 HPO4, then trim the buffer system with pH = 6?
1. We see the pH value for the wash. Tom on
the pH value is known for the concentration of ions in water:
pH = - lg = 6 or lg = -6. Zvidsi = 10-6 mol / l.
2. The buffering system in the acidity of the acid is in the form of ion H2 PO4
NaH2 PO4 Na + + H2 PO4 ¯ К2 (Н3 РО4) = 6.2 10 -8.
3. Knowing, the concentration of ions in water and the value of the constant
dissociation of acid, calculating the ratio of the concentration of acid to the concentration of salt in the buffer system:
C acid. |
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K2 (H3 PO4) |
abo = K2 (H3 PO4) |
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Z soli |
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1 10 - 6 |
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K2 (H3 PO4) |
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Calculation of the pH of buffer systems,
weak food and salts
Appendix 5. Calculate the pH of the buffer range, then take 0.1 mol / l NH4 OH
і 0.1 mol / L NH4 Cl, where the dissociation constant NH4 OH is expensive 1.79 10-5.
З (NH4 OH) = 0.1 mol / l
З (NH4 Cl) = 0.1 mol / l
КNH4OH = 1.79 10-5
1.pK NH 4 OH - lg 1.79 10 -5 - (0.25 5) 4.75
2.pH 14 - pKb. lg Pine.
Z soli
14 - 4.75 lg 0.1 9.25 0.1
Suggestion: pH = 9.25.
Appendix 6. Calculate the pH of the ammonia buffer system, then measure 0.5
ammonium hydroxide and ammonium chloride. Yak change in pH when added to
1 liter of total amount 0.1m HCI when added to 1 liter of total amount 0.1m NaOH and when diluted with water 10 times, where pK NH4 OH = 4.75?
C (NH4 OH) = 0.5 mol / l
З (NH4 Cl) = 0.5 mol / l
С (HCl) = 0.1 mol / l
С (NaOH) = 0.1 mol / l
p KNH 4 OH = 4.75
1. pH before dilution -?
2. pH for addition of HCI -?
3. pH for addition of NaOH -?
4. pH for dilution with water -?
pH 14 - рК lg З basic.
Z soli
1.pH 14 - 4.75 lg 0.5 0.5 9.25
2. When added to a buffer of 0.1m HCl, the concentration of NH 4 OH
change by 0.1 m and become equal
0.4 m, and the concentration of NH4 CI grows up to 0.6 m.
pH 14 - 4.75 lg 0.4 0.6 9.074
3. With the addition of 0.1 m NaOH up to 1 l of the total concentration of NH4 OH
decrease to 0.6 m, and the concentration of NH4 Cl will change to 0.4 m. As a result, we can measure: pH 14 - 4.75 lg 0.6 0.4 9.426
4. When diluted with water 10 times the size of the buffer: pH 14 - 4.75 lg 0.05 0.05 9.25
Appendix 7. Calculate рОН і pH range, then put 8.5 g of ammonia in 1 liter
107 g ammonium chloride.
m (NH3) = 8.5 g |
1. Known molar concentration |
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m (NH4 Cl) = 107 g |
ammonium chloride and ammonium chloride: |
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rON -? NS -? |
C (NH3) |
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C (NH 4 CI) |
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2. Calculated рОН и рН: |
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C main. |
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With salt |
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4,75 (0,6) 5,35 ; |
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Suggestion: pH = 8.65, pOH = 5.35 |
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Accrual of buffers |
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buffer |
sumyshi, as soon as you get out of the way |
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change 0.1m CH3 COOH і 0.1m CH3 COONa? |
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C (CH3 COOH) = 0.1 mol / l |
Fragments C (CH3 COOH) = C (CH3 COONa) = 0.1 m, then |
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З (CH3 COONa) = |
Vikor's formula: |
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0.1 mol / l |
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C A C B |
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0,12 |
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0.115 mol / l |
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| C (CH3 COONa) = | ||||||||||||||||||||
to that = K C |
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KCH 3 COOH = 18 10 -5 С = 1 mol / l |
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To lower the pH by one, you need to adjust the
number of moles of acid, at a rate of 10
Otzhe, it is possible to use the ryvnyannya:
INSPECTION FOR SELF-CONTROL
1. For more expensive pH sums, store in 100 ml of 23n HCOOH and 30 ml 15H
the range of NSOOK.
2. Yak change the pH of the buffer, folded with 0.01 Na 2 HPO4 i
0.01 m NaH2 PO4, when 10-4 mol of HCl is added.
3. Calculate the pH range, but 0.05 mol / l NH 4 OH і 0.05 mol / l
NH4 Cl (KNH4 OH = 1.8 10-5).
4. Calculate the buffer range, then add 0.4 mol Na in 1 liter 2 HPO4
i 0.2 mol NaH2 PO4.
In the case of a chemical analysis, it is often necessary to carry out a reaction in case of an invariable singing value. NS the difference. At the end of the day, it’s a bit of a buffer. NS when added to the range of strong acids (for example, HCl), lugs (for example, NaOH) and when diluted. Silent buffer solution is a sum of weak acid and salt (acid buffer system with pH< 7), слабого основания и его соли (основная буферная система, c pH >7), for a sum of sour and average salts.
The mechanism of the buffer action is visible on the butt of the acetate buffer.
The basis for the determination of the equilibrium reaction of the dissociation of weak acid:
(2)
The presence of a strong electrolyte CH3COONa, more often dissociated in the range:
Rivovagu (1) is severely damaged, so the concentration of undissociated CH3COOH molecules is practically expensive for the concentration of acid, and the concentration of ions CH 3 COO is an expensive concentration of salt:
For a diluted dissociation constant K d in the sum of CH 3 COONa, it is possible to transform through equally important concentrations of acid and salt:
, (4)
if the logarithm of the field (4) is negligible NS as a concentration of salt and acid.
(5)
= -lg K etc.
For organic acid and the value of todі 
Acetate buffer effect in dressings, when strong acid (for example, HCl) is added to a wide range of strong acids (for example, HCl), an excess of ionic water, which is the result of dissociation of strong acid,
call the anion of weak (low dissociating) octic acid , so wow
When added to the meadow (for example, NaOH) hydroxide-ion OH - neutralized with ocetic acid due to the statement of weak electrolyte - as a result of the reaction of neutralization:
In both drops, the concentration of ions in water and hydroxide-ions in the range practically does not change, in order to save the cob value NS.
Ammonium buffer solution is a sum of ammonium hydroxide and ammonium chloride. For an ammonia buffer, the pH value starts to be equal (6):
(6)
For ammonium hydroxide todi 
.
When an acid is added to such a range, or a meadow, neutralization of ions in water or a connection of hydroxide-ions into a weak electrolyte - ammonium hydroxide (on happy news- in hydrate amonia ):
At the same time, there is a value NS out of bounds.
When diluted with water, buffer systems save steel NS zavdyaky are careful to save the amount of acid and the ringing from the past, as it should start after the constant dissociation of a weak acid and a weak base.
Z rivnyan viplyvaє, scho NS the buffer does not change during dilution. However, the value of a decrease in the concentration of the buffer solution is reduced to an increase in the level of dissociation of weak electrolyte for a reason (2), that NS the buffer will change with strong dilution.
Buffer systems are characterized by two parameters:
1. The value of the opened cimi rose NS;
value NS in buffer systems it is determined by the value of the dissociation constant of a weak acid and a weak base: in acidic buffer systems (weak acid + strong acid) Z sour and її salt Z salt; in the main buffer systems (weak base + yogo strength) - in relation to the concentration of weak base Z main i yogo soli Z salt.
2. Buffer Umnist.
The buffer store is displayed differently behind the buffer warehouse. An important value, which characterizes the health of the buffer system and against changes in the reaction of the middle NS) With the addition of acids, is the buffer of the system.
the buffer The range is called the number of moles of acid in a meadow, when added to one liter (1 dm 3) of the buffer. NS on one.
The buffer Umn_st can be experimentally based or rorahuvati.
The capacity of buffer systems for continuous use NS not bezmezhno, won’t lay in a warehouse of the system and concentration of components. When significant amounts of a strong acid and a strong base are added to the buffer system, the change is spared NS.
The value of the buffer capacity of the system in terms of acid, or in the meadow, should be used according to the formula:
de Zі V- the concentration and the amount of added acid and in the lugh to the buffer size with the volume V buffer, - zmіna pH for the addition of acid in the meadow.
20. Buffer solutions, natural buffer systems. Rozrakhunok pH buffer systems, buffer mnіst.
buffer space- the solution, the concentration of ions in water (pH), which do not change from the addition of interfering quantities of strong acid in a meadow (div. Vodnevy indicator). B.R. It is composed of the sum of the range of weak acids and salts of a strong acid;
Bagato of natural rіdini are lined with buffer powers. Water in the oceans can be used as a buffer, which is rich in buffer power, in which case we can use carbon dioxide and hydrocarbonate-ions HCO3-. Dzherelom ostnіkh, crіm СО2, є a great amount of calcium carbonate in viglyadі shells, kreidanі and vapnyakіvіy in the oceans. Tsikavo, the photosynthetic activity of plankton - one of the main sources of acidity in the atmosphere, is to increase the pH of the middle soil to an increase. The price is based on the principle of Le Chatelle as a result of an efficient process when the carbon dioxide is coated with carbon dioxide. If, in the course of photosynthesis, CO2 is clearly seen, it will move to the right and the middle becomes larger. In cells of organism, CO2 hydration is catalyzed by the enzyme carbonic anhydrase.
Klіtinna rіdina, shelter also є with butts of natural buffer solutions. So, the roof should be avenged close to 0.025 mol / l in carbon dioxide Moreover, it is about 5% higher in choloviks than in females. Approximately the same concentration of hydrocarbonate-ions in the blood (it is also more in people).
Rozrahunok pH buffering systems.
for acidic buffer systems: pH = pK (Acid) + Lg.
For basic buffering systems:
pH = 14 - pK (submit) - lg 
de pK (acids), pK (pіdstavi) - negative tens of logarithm of the constant of electrolytic dissociation of weak acid; weak basis. Z tsikh rіvnyan can be seen The pH of the acidic (basic) buffer system is due to the nature of the weak electrolyte (pK (Acid) , pK (submit) ) I type of salt and acid concentration (submission).
Buffer - the ability to achieve a post-gradual concentration of singing ions (let it grow up to H + ions).
21. Acids and give according to Lewis.
Lewis's designation... Lewis proponuvav more information: acid - chain, yak accept electronic pair; pіdstava - tserechovina, yaka nadaє an electronic pair.
The interaction between acid and subordinate, according to the number of values, is due to the covalent linkage for the donor-acceptor mechanism:
On display at the Lewis value, all the specific ligands (NH 3, CN -, F -, Cl - and ін.) You can see them as shown, and all metals are like acids. The stage of the spore rate of the ion to the metal to the ligand is called the Lewis acidity, and the tendency of the ligand to establish the link with the ion to the metal is called the Lewis basicity... The strength of the acids and Lewis's rate can change in the presence of the nature of the partner.
22. Heterogeneous ravnovagi. Tvir razchinnosti.
Equivalent in a heterogeneous system
in the system for the minds there is a flexible transition of speech from one phase to the insha. I also know that the system can also be located in the rivnovazi, tobto. E. Do not be aware of the transition of any component from one phase to the first, є the parity of the chemical potentials of this component in the developed phases.
One of the most important laws of heterogeneous equilibrium is the rule of phases. Vono operates with the basic understandings about the components, phases and number of steps of freedom. Two of the first to understand the meaning of the vision.
Along the thermodynamic steps of freedom, be free to linger on the independent parameters of the system, be located in the thermodynamic level, which can take up a significant value in the singing interval, and the number of phases does not change.
The number of steps of freedom (the variance of the system) is the same number, as specified, with the number of parameters that characterize the mill of an equally important system, it is possible to give a significant value without the fact that the number of phases in the system is changing.
Phase rule: In an isolated system of critical importance, the number of phases plus the number of steps of freedom and an additional number of components plus 2
twir of reliability (NS, K sp) - concentration of ions of poorly soluble elektrolіtu in yogo hackneyed discord at constant temperature and vice. Tvir razchinnosti - the value of the post.
Please follow the Henderson - Hasselbach values for the pH buffer solutions:
- for acid buffer rivnyannya maє viglyad
- for the main buffer
Show that the pH of the buffer value given to the warehouse should be set to the concentration of acid and salt, or at the same time and salt, so that it does not lie in the dilution. When changing, the difference in the concentration of the skin component changes in the same number of times.
buffer
The buffering capacity of the buffer has been adjusted to the correct pH value. In order to add acid or, at the same time, do not change the pH of the buffer, it is possible only in the adjacent quantities.
The value that characterizes the capacity of the buffer against the reaction of the middle course at the addition of acids and the meadow is called the buffer range (B).
Buffer The range is determined by a number of moles of the same strong acid in a meadow, adding up to 1 liter of buffer to a change in pH per unit.
Mathematically, the buffer is the beginning of the rank:
In acid (mol / L mule mmol / L):
,
de n (1 / z HA) - number of mol of acid equivalents, pH 0 and pH - buffer pH up to and after acid addition, V B - buffer volume.
In the meadow (mol / l or mmol / l):
,
de n (1 / z GET) - the number of moths of equivalents in the meadow, which is also indicated.
The buffer is based on a number of factors:
1. From nature, speech and components are added to the buffer. Oscillations of deyaky speeches can confirm unrelated spillovers or complexes or give some undesirable reactions with the components of the buffer system, so that the understanding of the buffer capacity consumes the senses.
2. Vidnaya concentration of components in the buffer system.
chim more the components in the acid-base bet in the range, which are more buffer.
Between the ratio of the concentrations of the components of the buffer, the system is still more and more powerful. The interval pH = pK ± 1, called the zone of the buffer system. The rate of change to the interval of performance From salt / S to-ty from 1/10 to 10/1.
B to (blood) = 0.05 mol / l; B to (plasmi) = 0.03 mol / l; B to (siv.blood) = 0.025 mol / l
Buffer blood systems
Especially great is the value of the buffer system in the presence of acidic-puddle organisms. The pH value of the inner cells is in the range from 6.8 to 7.8.
Acidic - the main level in the blood of people is provided with hydrocarbonate, phosphate, protein and hemoglobin buffer systems. The normal pH of blood plasma is 7.40 ± 0.05.
Hemoglobin buffer system 35% will provide a buffer of blood: 
... Oxyhemoglobin is a strong acid, less hemoglobin renewal. Oxyhemoglobin squeak up the beetle in the eyes of the high salt.
Carbonate buffer system :
for your exertion, sit at the first place. Vona is represented by vugilnoy acid (H 2 CO 3) and sodium bicarbonate or sodium bicarbonate (NaHCO 3, KHCO 3) in a proportion of 1/20. Bicarbonate buffer is widely used for the improvement of acid-base deterioration in the body.
Phosphate Buffer System 
.
Dihydrophosphate possesses the power of a weak acid and in conjunction with the need for household products. Hydrophosphate of weak meadow power and entering into a reaction with stronger acids.
Bilkova buffer system plays the role of neutralization of acids and meadows with amphoteric powers: in the acidic middle of the food, plasmas are produced, in the basic - like acids: 
Buffer systems in tissues, when the pH of the tissues is adjusted to the level of steel. The head buffers are tissues є bilky and phosphates. The pH adjustment also helps the lungs and nirok. Through the legends, the excess in carbon dioxide is removed. Nirks with acidosis see more acidic monobasic sodium phosphate, and with alkalosis - more salts: dibasic sodium phosphate and sodium bicarbonate.
Set up tasks
Decision:
Rosrakhovuєmo pH of acidic buffer according to the formula, todі
as follows: 5,76
Decision:
Rozrakhovuєmo buffer mnist for the formula: 
as follows: 0.021 mol / l
Butt 3.
The buffer solution should be stored in 100 ml of 0.1 mol / l ocetic acid and 200 ml of 0.2 mol / l sodium acetate. It will change the pH of the whole range, when up to 30 ml of 0.2 mol / l will change with sodium hydroxide.
Decision:
Rosrakhovuєmo pH of the buffer will be adjusted according to the formula:
When NaOH is added to the buffer, the amount of salt decreases and the amount of acid in the buffer decreases:
0,006 0,006 0,006
CH 3 COOH + NaOH = CH 3 COONa + H 2 O
Rozrakhovuєmo n (NaOH) = 0.03 L · 0.2 mol / L = 0.006 mol, while in the buffer the amount of acid decreases by 0.006 mol, and the amount of salt decreases by 0.006 mol.
Rosrakhovuєmo pH range according to the formula:
Zvidsy: pH 2 - pH 1 = 5.82 - 5.3 = 0.52
as follows: pH buffer value = 0.52.
zavdannya for independent solution
4. On titration of 2 ml of blood for changing the pH from the cob value (7.36) to the end value (7.0), 1.6 ml of 0.01 M solution of HCl is required. Buff the acid buffer.
5. A small amount of sodium acetate should be added up to 300 ml of ocetic acid to reduce the concentration of ions in water by 300 times (K dis (CH3COOH) = 1.85.10 -5).
6. In case of biochemistry, phosphate buffer with pH = 7.4. In any case, the need for the reduction of sodium hydrogen phosphate and sodium dihydrogen phosphate at a concentration of 0.1 mol / l for skin, the removal of such a buffer solution (рК (Н 2 РО 4 -) = 7.4).
7. Yaki poroshennya KOS is susceptible to the following indicators: blood pH = 7.20, PCO 2 = 38 mm Hg. Art., BO = 30 mmol / L, SBO = -4 mmol / L. Yak stick to the dane of the ruined KOS?
tests
Buffer rozchin vikoristovoyt for adjustment of constant pH value. Wines are stored from the sum of weak acids ON and from the received delivery A -. Buffer design has the following properties:
HA + H 2 O ↔ H 3 O + + A -
A - + H 2 O ↔ HA + OH -
drive one one when reaching high C (HA) and C (A -); To that you can vvvat, scho [HA] = C (HA) і [A -] = C (A -). Vikoristovuchi viraz for To a ONі unhuggedly outside [H 3 O +] for the dissociation of water, we will
The same viraz can be trimmed, vicoristovuchi constant of another rivnovagi.
APPENDIX 16. Protect the pH buffer from 0.10 M sodium acetate and 0.10 M sodium acetate.
Decision. Here you can see all the words that allow you to use the formula (2-14) (ostic acid is a weak acid, the concentration of acid and the resulting amount is enough). Tom
APPENDIX 17. Protect the pH buffer from 0.10 M ammonium and 0.20 M ammonium chloride.
Decision. For the formula (2-14) we know
An important characteristic of the buffer is the buffer. The addition of a strong supply (acid) to a buffer, the pH value can be changed with a change in the concentration of acid HA and the resulting supply A -. It is accepted to represent this buffer at the viglyad
there is a serious reason to reach the buffer.
Strong acid must be added to the buffer. Let us write down the value of the material balance for the sum of the monobasic acid ON and the resulting submission A -:
Vislovimo [ON] via To a ON and it is presented in the balance of material balance. We know [A -]:
(2-17)
Differentiating rivnyannya (2-17) by dpH from urahuvannya, scho dc main =, can be recognized
(2-18)
It is not important baciti, at pH = Pk and HA, tobto - C (HA) = C (A -), the maximum buffer capacity is reached. You can show me
(2-19)
Formulas (2-18) і (2-19) viplivayut one from іншої, if you guess, scho [HA] = a(HA) C (HA) i [A -] = a(A -) C (A -), as well as virazi for a(HA) i a(A -).
For highly diluted buffer solutions, it is necessary to add water dissociation. At the same time, the rivnyannya (2-19) will speed up:
Here, the first two additions describe the buffer for water, the third for the buffer for acid and the resulting presentation.
APPENDIX 18. Open, as the pH changes, up to 1.0 l of the buffer solution, store in 0.010 M ocetic acid and 0.010 M sodium acetate, add 1.0 · 10 -3 mol of hydrochloric acid.
Decision. Adjust the pH value of the buffer to the addition of hydrochloric acid:
Zagalnaya concentration of buffer
To do this, add a concentrated buffer to the size of the buffer.
Rozrahunok ale formula (2-19) and the same result:
Rosrahovuєmo zmіna pH
Thus, for the addition of hydrochloric acid and pH buffer in the warehouse
pH = 4.75 - 0.087 = 4.66
The price can be viralized, not by releasing the buffer capacity, but by knowing the number of components in the buffer sum before and after the addition of HC1. At the outset
APPENDIX 19... Vive the viraz for the maximum buffer capacity of the range from the concentration of ingredients in the village.
Decision. You know, wash, for which the buffer capacity is maximum. For the whole, we will differentiate viraz (2-18) by pH and generally will be zero
Zvidcy [H +] = K a HA i, also, C (HA) = C (A -).
Vikoristovuchi formulas (2-19) і (2-21),
Rozrakhunok pH sum of acids abo p_dstav. Do not mix up two acids ON 1 and ON 2. If one acid is stronger than it is, then the more weak acid may be present, so the dissociation is reduced. In general, it is necessary to dissociate both acids.
If HA 1 and HA 2 are not even worse than weak acids, then the unstable water auto-test, the level of electroneutrality can be written in the viewer:
[H 3 O +] = [A 1 -] +
We know of the equally important concentration A 1 - and A 2 1 s viraziv for dissociation constants HA 1 and HA 2:
By the way, we disregard virazi in the field of electrical neutrality
Pislya re-creation will be recognized
If the steps of acid dissociation do not overtake 5%, then
For the sum NS acids
Similarly for the sum of monobasic offices
(2-21)
de Up to a 1і Up to a 2 - dissociation constants of binding acids. At a practical level, it’s possible to understand the situation, if one (one) of the present in the amount of acids (submission) has brought in the dissociation of the latter, and for that, for the development of pH, it is possible to dispose of the dissociation of the acids. Alle, you can create and understand situations.
APPENDIX 20. Increase the pH of the sum, in the general concentration of benzoic and aminobenzoic acids, approximately 0.200 and 0.020 M.
Decision. I want the value of the dissociation constants of benzoin (Before a= 1.62 · 10 -6, significant Up to 1) i aminobenzoic (Up to a = 1.10 · 10 -5, significant K 2) Acids grow up to two orders of magnitude, after reaching a large increase in the concentration of acids, it is necessary to dissociate both acids. Behind the formula (2-20) we know
