A buffer is a solution that can resist pH change upon the addition of an acidic or basic components. It is able to neutralize small amounts of added acid or base, thus maintaining the pH of the solution relatively stable.
A buffer consists of a weak acid and its conjugate base or a weak base and its conjugate acid. Buffer capacity is the amount of acid or base that can be added before the pH of a buffer changes. An example of a buffer solution is bicarbonate in blood, which maintains the body's internal pH.
Buffers work by neutralizing any added acid (H+ ions) or base (OH- ions) to maintain the moderate pH, making them a weaker acid or base.
A solution of acetic acid and sodium acetate (CHCOOH + CHCOONa) is an example of a buffer that consists of a weak acid and its salt. An example of a buffer that consists of a weak base and its salt is a solution of ammonia and ammonium chloride (NH(aq) + NHCl(aq)).
|Buffering agent||pK||Useful pH range|
|Citric acid||3.13, 4.76, 6.40||2.1–7.4|
Buffer Solution Examples
Feb 17, 2022
A buffer is a mixture of a weak base and its conjugate acid mixed together in appreciable concentrations. They act to moderate gross changes in pH . So approx. equal concentrations of a weak base with its conjugate acid, or addition of half an equiv of strong acid to weak base, will generate a buffer.
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A good buffer generally contains relatively equal concentrations of a weak acid and its conjugate base. Many different factors must be considered in choosing a good buffer, the most important being the ionic strength and the UV absorbance at low wavelength.
Add water to make up to 1 L. Add water to make up to 1 L. Add water to make up to 1 L. (Alternatively, dilute 100 mM phosphoric acid (sodium) buffer solution (pH=6.8) ten times.)
The strongest buffers are those composed of strong acids and strong bases. When pH = pKa, the weak acid and salt concentrations in a buffer are equal.
Data obtained by Buchanan and Peterson (2) show that milk is a more efficient buffer in the range pH 5.0 to 6.0 than it is at higher pH values.
Human blood contains a buffer of carbonic acid (HCO) and bicarbonate anion (HCO) in order to maintain blood pH between 7.35 and 7.45, as a value higher than 7.8 or lower than 6.8 can lead to death. In this buffer, hydronium and bicarbonate anion are in equilibrium with carbonic acid.
Background: Alka-Seltzer contains sodium bicarbonate and citric acid. The sodium citrate acts as an antacid. Excess sodium bicarbonate from the Alka-Seltzer acts to neutralize base.
Vinegar is a solution of a weak acid called acetic acid, CHCOOH; its conjugate base is the acetate ion, CHCOO . Since sodium acetate dissociates in water to yield acetate ions and sodium ions, adding sodium acetate to an acetic acid solution is one way to prepare an acetic acid buffer.
For example, the buffering of pure sulfuric acid at its second pK is, theoretically, 0.57 Eq/mol-pH and falls off very rapidly at pH values removed by more that 1 pH - just like any other acid.
Hint: Neutral buffer is a buffer solution which is produced by mixing weak acid (carbonic acid, acidic acid) and weak base (ammonia, pyridine and methylamine). Ammonium hydroxide and acetic acid are good examples of neutral buffer solutions.
|Name of the drink||Trade name||Manufacturer|
|Orange juice||Real orange fruit juice||Dabur foods Pvt Ltd, India|
Carbonated beverages, especially coke has highest pH and buffering capacity followed by Fanta and Sprite. These results provide further information to the dentist regarding carbonated beverages and commercial fruit juices and their potential role in the development of erosion.
Note that the maximum buffer capacity of lemon juice is at a pH of 4.4 which is in close agreement with the dissociation exponent of the second dissociation constant of citric acid (pKa2 = 4.39-4.50). Curve A also shows in detail that the buffer capacity of lemon juice is between pH 2.7 and 5.6.
Diet Pepsi has the highest buffering capacity (5.38 mL of 0.5 M NaOH), regular Selection Cola (3.78 mL of 0.5 M NaOH) has the lowest buffering capacity, and Coca Cola (3.79 mL of 0.5 M NaOH) is very similar and not significantly different from Selection Cola.