What is a buffer and what is its use?
Answer:
A buffer is a solution consisting of a weak base and its salt or a weak acid with its salt. The salt in each case provides the conjugate acid and base, respectively so that an equilibrium is formed:
HA + H2O = A- + H3O+
Keq= [A-]*[H3O+]/[HA] (parenthesis mean concentrations of a species)
The function of a buffer is to keep the pH relatively steady, with only small changes upon the addition of a base or acid. Many biological reaction use buffers, because enzymes have high activities at a specific pH's. One of such buffers is our blood (HCO3-/H2CO3)
An equation called Henderson-Hasselbalch equation describes the changes of pH:
pH=pKa+log[A-]/[HA]. Since you have a logarithm of [A-]/[HA], a small change in either the numerator or denominator is not going to affect the pH much. For example, you add 0.1 M H+ to a buffer made from 1 M A- (conjugate base) and HA (Acid). A new equilibrium would be reached changing the A- to 1-0.1=0.9 M and HA from 1 to 1+0.1=1.1 M (as A- will react with H+ according to the equation above). Initially pH=pKa+log(1/1)=pKa, upon the addition of 0.1 M H+ it will change to pH=pKa+log(0.9/1.1)=pKa-0.09 - a very small change indeed.
slows a reaction down
the opposite of it would be a catalyst which speeds up the reaction rate
hope that helped
Buffer solutions are solutions which resist change in hydronium ion and the hydroxide ion concentration (and consequently pH) upon addition of small amounts of acid or base, or upon dilution. Buffer solutions consist of a weak acid and its conjugate base (more common) or a weak base and its conjugate acid (less common)
Simply put, a buffer is a solution that resists a change in pH. If you add a base or an acid to a buffer, the pH changes only slowly, as compared to a non-buffered solution. Buffers are made from weak acids or bases and their conjugate. For example, a buffer could be made from acetic acid (CH3COOH) and sodium acetate (CH3COONa). Buffers occur often in biological processes. Blood is a buffer; in order for certain enzymes to function properly, they must be used at a certain pH. Blood's buffering ability allows it to remain at that vital pH, even if other chemicals are released into the bloodstream.
Buffer is a solution whose pH does not change by addition of small amount of acid or alkali.
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