Chemical Article : buffer
BUFFER
English: Buffer solution- Buffer capacity for pKa = 7 as percentage of maximum (Photo credit: Wikipedia)
PH of a solution will decrease when added acid, this is due to increased concentration of H + . Conversely, when added base will raise the pH because the addition of base increases the concentration of OH - .Addition of water to acidic and basic solutions will change the pH of the solution, as the concentration of acid or base will decrease. However, there is a solution that when added a little acid, base, or water does not change the pH significantly. Such a solution is called a buffer solution (also called buffer or buffer solution ). The buffer solution has an acid component which can withstand the increase in pH and basic components which can withstand pH decline. The component is a conjugate of weak base acids making up the buffersolution itself. Thus, the buffer solution is a solution formed by the reaction of a weak acid with its conjugate base or a weak base with its conjugate acid. This reaction is called a conjugate acid-base reaction. (Keenan et al. , 1980)
In general, the buffer solution is described as a mixture comprising:
- The weak acid (HA) and its conjugate base (A - ions ), this mixture yields an acidic solution.
- The weak base (B) and its conjugate base (BH + ), this mixture yields an alkaline solution. (Purba, 1994)
The buffer solution component is divided into (Keenan et al., 1980):
- Acidic buffer solution
This solution maintains a pH in the acid region (pH <7). This solution can be prepared from the weak acid and its salt (which is the conjugate base of the acid). The other way is to mix a weak acid with a strong base, weak acid mixed in excess amount. The mixture will produce a salt containing the conjugate base of the corresponding weak acid. In general strong base used such as sodium hydroxide, potassium hydroxide, barium hydroxide, calcium hydroxide, and others.
- The alkaline buffer solution
This solution maintains the pH at the base region (pH> 7). This solution can be made from weak bases and salts (derived from strong acids). The other way is: mixing a weak base with a strong acid where the weak base is mixed in excess.
The properties of the buffer solution are known as follows (Syukri, 1999):
- Has a certain pH
PH buffer can be searched with Henderson-Hasselbalch equation, that is:
PH = pKa + log [salt] / [acid]
POH = pKb + log [salt] / [base]
The buffer pH depends on the weak acid Ka or weakly basic Kb and the ratio of the acid concentration to the conjugate base concentration or the weak base concentration with the conjugate acid concentration. The similarity (Purba, 1994):
A. Weak acid ionization reaction:
HA (aq) ↔ H + (aq) + A - (aq)
The ionization constant is denoted by Ka
Ka = [H + ] [A - ] / [HA]
B. Reaction of weak base ionisation:
LOH (aq) ↔ L + (aq) + OH - (aq)
The ionization constant is denoted by Kb
Kb = [L + ] [OH - ] / [LOH]
- Its pH is relatively unchanged if added slightly acid or base.
- Its pH does not change if it is diluted.
It has been mentioned that the buffer solution contains both acidic and basic components with their conjugate acids and bases, which can bind both H + ions and OH - ions . So that the addition of a few strong acids or strong bases does not change the pH significantly. Here's how the buffer solution works (Syukri, 1999):
Acid buffer solution
For example how it works can be seen in buffer solutions containing CH 3 COOH and CH 3 COO - which are equilibrium. The process is as follows:
- On the addition of acid
The addition of acid (H + ) will shift the equilibrium to the left. The added H + ions react with CH 3 COO - forming CH 3 COOH molecules .
CH 3 COO - ( aq ) + H + ( aq ) → CH 3 COOH ( aq )
- On the addition of a base
If the added is a base, then the OH - ion of the base will react with the H + ion to form water. This will cause the equilibrium to shift to the right so that the concentration of H + ions can be maintained. Thus, the addition of a base causes a reduction in the acid component (CH 3 COOH), not the H + ion . The added base reacts with CH 3 COOH acid to form CH 3 COO - and water ions .
CH 3 COOH ( aq ) + OH - ( aq ) → CH 3 COO - ( aq ) + H 2 O ( l )
The basic buffer solution
As an example of how it works, it can be seen in a buffer solution containing NH 3 and NH 4 + that is equilibrium. The process is as follows:
- On the addition of acid
If an acid is added, then the H + ion of the acid will bind the OH - ions . This causes the equilibrium shifts to the right, so that the concentration of ions OH - can be maintained. Additionally, this addition causes a reduction in the base component (NH3 ), not the OH - ion . The added acids react with the NH 3 base to form the NH 4 + ion.
NH 3 ( aq ) + H + ( aq ) → NH 4 + ( aq )
- On the addition of a base
If that is added is a base, the equilibrium shifts to the left, so that the concentration of ions OH - can be maintained. The added base reacts with the acid component (NH 4 +), forming the basic components (NH 3 ) and water.
NH 4 + ( aq ) + OH - ( aq ) → NH 3 ( aq ) + H 2 O ( l )
To calculate the pH of buffer solution is used the following way (Purba, 1994):
- Acid buffer solution
Can be used ionizing constants in determining the concentration of H + ions in a solution of the following formula:
[H + ] = K a xa / g or
pH = p K a - log a / g
pH = p K a - log a / g
With, K a = weak acid ionization constant
a = number of moles of weak acid
g = number of moles of conjugate base
a = number of moles of weak acid
g = number of moles of conjugate base
- The basic buffer solution
Can be used ionizing constants in determining the concentration of H + ions in a solution of the following formula:
[OH - ] = K b xb / g or
pH = p K b - log b / g
pH = p K b - log b / g
With, K b = weak base ionization constant
b = number of moles of weak base
g = number of moles of conjugate acid
b = number of moles of weak base
g = number of moles of conjugate acid
According to Syukri (1999), buffer solution also has buffer capacity (commonly calledbuffer index or buffer intensity ). The buffer capacity is a measure of the buffer's abilityto maintain a constant pH when added strong acid or strong base. The buffer capacity depends on the amount of acid-salt or salts contained therein. When the amount is large, the shift in equilibrium to the right or left can take a lot to compensate for the strong acid or strong base added. So it can be called its large buffer capacity .Conversely, if the amount of salts or salts is small, it can cause a shift in equilibrium to the right and left slightly. So it can be said its buffer capacity is small. A buffer can withstand the change of [H + ] as much as 100x initially . The only permitted pH change is only about 2. Ka or Kb are constants, then a buffer is only effective at certain pH regions called buffer area ranges . Actually adding acid / base to a buffer will change its pH, but the change is very small and can be ignored. However, if the amount of acid / base is added more and more, then the pH change can not be ignored anymore. The amount of acid or base that can be neutralized by a bufferbefore the pH of the solution is changed is called the buffer capacity .
The capacity of the buffer solution depends on the number of moles and the mole ratio of the buffer components. The more mole the buffer component, the greater the ability to maintain the pH. If the acid component is too small, the addition of a bit of base may change the pH. Conversely, if the component of the base is too small, the addition of a bit of acid may change its pH. Meanwhile, the mole ratio between the components of a buffer solution should be between 0.1-10. Beyond that comparison, the buffer properties will decrease (Keenan et al. , 1980).
This buffer solution can be seen in everyday life such as in medicine, photography, leather industry and dye. In addition to these applications, there is application of the concept of buffer solution in the human body, for example as in body fluids. Body fluids (both intracellular fluids and extracellular fluids) are buffer solutions. The main buffer system in intracellular fluid is a pair of dihydrogenphosphates-monohydrogenphosphate (H 2 PO 4 - -HPO 4 2- ). While the main buffer system in the extracellular fluid is the carbonic-bicarbonate acid (H 2 CO 3 - HCO 3 - ) pair . This buffer system can keep blood pH almost constant, which is about 7.4 (Keenan et al ., 1980).
The conclusion of what example you get. Explain?
BalasHapusConclusion Material Buffer Buffer (buffer)
Hapus1. The buffer solution is a solution whose pH is practically unchanged even if slightly acidic, slightly alkaline, or diluted.
2. The acid buffer solution is composed of the weak acid and its conjugate base.
3. The base buffer solution is composed of weak base and conjugate acid.
4. The working principle of acid buffer solution on the effort to change the pH:
Addition of a little acid: A- (aq) + H + (aq) à HA (aq)
The addition of a bit base: HA (aq) + OH- (aq) à A- (aq) + H2O (l)
Dilution can be ignored because the addition of H + ions from water is too small
5. The working principle of the alkaline buffer solution on the effort to change the pH:
Addition of slightly acid: B- (aq) + H + (aq) à BH (aq)
The addition of a bit base: BH + (aq) + OH- (aq) à B (aq) + H2O (l)
Dilution can be ignored because the addition of H + ions from water is too small
6. The acid buffer solution can be prepared by dissolving into water:
Weak acid and salt
Excessive acid and a strong base
Excessive acid salt salts and a strong acid or base
7. The alkaline buffer solution may be prepared by dissolving into water:
Weak base and salt
Excess weak base and a strong acid
Excessively weak base salts and a strong acid or base
8. The pH of the buffer solution can be calculated by the formula:
9. The buffer solution plays an important role in everyday life, even in the process within the body of a living being.
how buffer in our body?
BalasHapusThere are two namely on:
Hapus1. Blood as a buffer solution
There are several factors involved in the control of blood pH, including carbonate buffer, hemoglobin buffer and phosphate buffer.
A. Carbonate Buffer
The carbonate buffer is derived from a mixture of carbonic acid (H 2 CO 3) with a bicarbonate conjugate base (HCO 3).
H 2 CO 3 (aq) -> HCO 3 (aq) + H + (aq)
Carbonate buffer plays an important role in controlling blood pH. Marathon runners may experience acidosis, which is a decrease in blood pH caused by a high metabolism that increases the production of bicarbonate ions. This acidosis condition can lead to heart disease, kidney, diabetes miletus (diabetes) and diarrhea. People who climb mounts without additional oxygen can suffer from alkalosis, which is an increase in blood pH. Minor oxygen levels in the mountains can make climbers breathe faster, so too much carbon dioxide is released, whereas CO 2 is water-soluble producing H 2 CO 3. This causes the blood pH to rise. The condition of alkalosis can lead to hyperventilation (excessive breathing, sometimes because of anxiety and hysteria).
B. Buffer of Hemoglobin
In the blood, there is a hemoglobin that can bind oxygen to subsequently carried to all body cells. The equilibrium reaction of the oxyhex hemoglobin buffer solution is:
HHb + O 2 (g) «HbO 2 - + H +
Hemoglobin acid hemoglobin action ions
The presence of oxygen in the above reaction can affect the concentration of H + ions, so that the blood pH is also affected by it. In the above reaction O 2 is alkaline. Hemoglobin that releases O 2 can bind H + and form hemoglobin acid. So that the H + ion released in decomposition H 2 CO 3 is an acid produced by CO 2 dissolved in water during metabolism.
C. Phosphate Buffer
In the intra-cell fluid, the presence of a phosphate buffer is essential in regulating blood pH. This buffer is derived from a mixture of dihydrogen phosphate (H 2 PO 4 -) with monohydrogen phosphate (HPO 3 2-).
H 2 PO 4 - (aq) + H + (aq) -> H 2 PO 4 (aq)
H 2 PO 4 - (aq) + OH - (aq) -> HPO 4 2- (aq)) + H 2 O (aq)
The phosphate buffer can maintain a blood pH of 7.4. External buffers are few in number, but are essential for a buffer solution.
2.Air water as a buffer solution
Teeth can dissolve if inserted in a strong acid solution. Email the damaged tooth can cause germs into the tooth. The saliva can keep the pH at the mouth of about 6.8. Saliva contains a phosphate buffer solution that can neutralize the acid formed from the fermentation of food scraps.
If you wash your hands with soap that is wet with beach water that has concentrated concentrated salt. What happened ?
BalasHapusSea water contains many minerals, especially Sodium ions. When you rinse your hands with salt water (seawater), Sodium ions contained in soap molecules will be difficult to soluble in water because salt water already contains many Sodium ions, even too much. This makes soap will be difficult to remove dirt, take it away.
HapusExplain the cause of the equilibrium shift.
BalasHapusEquilibrium is the balance so Changes from the original equilibrium state to a new equilibrium state because external action or influence is known as equilibrium shift (Martin S. Silberberg, 2000). Factors that may affect the equilibrium shift are:
Hapus1. Changes in the concentration of one substance
2. volume or pressure changes
3. temperature changes
BalasHapusWhat is the reason of a solution so that it can maintain its ph?
The working principle of acid buffer solution in maintaining pH is as follows:
HapusAny addition of H + will be neutralized by the conjugate base.
Any addition of OH- will be neutralized by a weak acid.
Any dilution with H2O means increasing the number of H + ions and the conjugate base of weak acid ionisation but the addition of H + concentration becomes meaningless as the volume of the solution also increases.
The working principle of the basic buffer solution in maintaining the pH is as follows:
Any addition of H + will be neutralized by a weak base.
Any addition of OH- will be neutralized by conjugate acid.
Any dilution with H2O means increasing the amount of OH- ions and conjugate acid from weak base ionisation, but the addition of OH-concentration becomes meaningless because the volume of the solution is also increased.
what is the funcition of buffer in real life
BalasHapusThe buffer solution in everyday life
HapusFunction Solution in the human body
The chemical reactions occurring within the human body are enzymatic reactions, ie reasks involving enzymes as catalysts. Enzyme as catalyst can only work well at certain pH (optimum pH). In order for enzymes to remain optimum, a reaction environment with a relatively fixed pH is required, therefore a buffer solution is required.
In each body fluid there is a conjugate acid-base pair that acts as a buffer solution. Body fluids, both as intra-cell fluids (in cells) and extra cell fluid (outside the cell) require the buffer system to maintain the pH value of the liquid. An important extra-cell support system is a carbonate (H2CO3 / HCO3-) buffer that plays a role in maintaining blood pH, and a phosphate buffer system (H2PO4- / HPO42-) that plays a role in maintaining the pH of the intra-cell fluid.
Function The buffer solution in the industry
In the pharmaceutical industry, buffer solution plays a role for the manufacture of drugs for the active substance of the drug has a certain pH. In addition, buffer solution is also used for the food and beverage industries such as those commonly used are sodium acetate and citric acid.
Examples of citric acid are:
Citric acid is a weak organic acid found in leaves and fruits of Citrus genus (citrus). This compound is a good and natural preservative, besides being used as a sour flavor enhancer in foods and soft drinks. In biochemistry, citric acid is known as an intermediate in the citric acid cycle, which is important in the metabolism of living things, so it is found in almost all living things. This substance can also be used as an environmentally friendly cleaning agent and as an antioxidant.
Citric acid is found in various types of fruits and vegetables, but is found in high concentrations, which can reach 8% dry weight, in lemon and lime (eg lime and lime).
The citric acid chemical formula is C6H8O7 (its structure is shown in the information table on the right). This acid structure is reflected in the name of its IUPAC, 2-hydroxy-1,2,3-propaniccarboxylic acid.
The physical properties of citric acid are summarized in the table on the right. The acidity of citric acid is obtained from three COOH carboxyl groups which can release protons in solution. If this happens, the resulting ions are citrate ions. Citrate is best used in a buffer solution to control the pH of the solution. Citrate ions can react with many metal ions to form citrate salts. In addition, citrate can bind metal ions with chelating, so they are used as a preservative and water hardener
Buffer Buffer Function
Buffering solutions are essential in life; For example in chemical analysis, biochemistry, bacteriology, dye, photography, and leather industry. In the field of biochemistry, tissue and bacterial cultures undergo a very sensitive process to changes in pH. The blood in the human body has a pH range of 7.35 to 7.45, and if the human blood pH above 7.8 will cause the human organ to be damaged, it must be kept within the pH range with buffer solution.
what the meaning of PH?
BalasHapusPH is the degree of acidity used to express the level of acidity or alkalinity possessed by a solution.
Hapus