What is a buffer? Chemistry Definition

What is a buffer?

A knowledge of buffer systems is essential for chemists to correctly design cosmetic and household products as well as nutritionists to design diets. Enzymes, catalysts that expedite chemical reactions, in the human body, operate most effectively at specific pHs.

Buffer systems are chemical formulations of acids, bases and salts that resist changes in acidity or alkalinity (changes in pH) when  strong acids and bases are added to the buffer solution.

There are two primary types of buffer systems in chemistry, acidic buffers and alkaline buffers. An acidic  buffer is a chemical solution formulated with a  weak acid and the salt of the weak acid's conjugate base. For example, a solution of NACH3COO, sodium acetate,  and CH3COOH,acetic acid, is a acidic buffer solution, or system. Sodium acetate is a salt of a weak acid's conjugate base (CH3OO-).

Other examples of acidic buffer solutions include a mixture of ethanoic acid and sodium ethanoate

CH3COOH(aq) ethanoic acid
NACH300, Sodium Ethanoate

Ethanoic acid is the weak acid, and sodium ethanoate is the salt of the weak acid's conjugate base (CH3C00-).

More simply put, an acidic buffer solution is the mixture of a salt and an acid where the salt and the acid have a common ion (the common ion effect). For a buffer system composed of sodium acetate and acetic acid, the common ion is C2H3C00-. Doe ethanoic acid and sodium ethanoate the common ion ethanoate (CH3COO-)

An alkaline buffer system can  be formulated with a weak base and the salt of its conjugate acid. For example, ammonia, the weak base,  and ammonium chloride, the salt of conjugate acid of ammonia (the weak base) when mixed together form an alkaline buffer solution.


Ammonia: NH3
Ammonium Chloride: NH4Cl

NH4Cl(aq) → NH4+(aq) + Cl-(aq)
NH3(aq) + H2O(l) –> NH4+(aq) + OH-(aq)

NH3 is the weak base, and NH4Cl is the salt of NH3's conjugate acid(NH4+).  Similarly, NH4+ is the common ion of the weak base and tNthe H4Cl is salt of the weak bases' conjugate acid (NH4+).


References:

What is a buffer, About.com, http://chemistry.about.com/od/acidsbase1/a/buffers.htm

Buffer Solutions, Chemguid.co,uk,  http://www.chemguide.co.uk/physical/acidbaseeqia/buffers.html

Buffers Containing a Base and a Conjugate Acid, Boundless, Better than your Textbook, https://www.boundless.com/chemistry/acid-base-equilibria/buffer-solutions/buffers-containing-a-base-and-conjugate-acid/


Buffer Solutions: Introductions and Uses: http://www.knockhardy.org.uk/sci_htm_files/08buf.pdf

Exercises-Sample Tests

Acid Base Reactions, Multiple Choice Questions with Answers: http://www.oneonta.edu/faculty/kotzjc/REVIEW/Ch18_Rxn.pdf