Biochemistry 461 Fall, 2015, Lecture 4 Acid:Base Equilibria ConAnued Reading & Problems: Please see the syllabus Extra problems will be posted on the Web Site
Dec 10, 2015
Biochemistry 461 Fall, 2015, Lecture 4
Acid:Base Equilibria ConAnued Reading & Problems: Please see the
syllabus Extra problems will be posted on
the Web Site
Today’s topics
• Acid-‐base and buffer calculaAons
What is a buffer, buffering capacity, buffer preparaAon, response of a buffer to strong acid or base.
• PolyproAc Acids
Buffer
• a substance capable in soluAon of neutralizing both acids and bases and thereby maintaining the original acidity or basicity of the soluAon; also : a solu(on containing such a substance
The Buffering Capacity of a Dog
• Swan & Pi)s Experiment (1952) Summary: Dogs received an infusion of 14 mmols H+ per litre of body water and the pH dropped from 7.44 to 7.14.
hXp://www.anaesthesiamcq.com/AcidBaseBook/ab2_2.php#ref
Strong versus Weak Acids (& Bases)
• Strong acids & bases • Weak acids & Bases: – How do we quanAfy relaAve strength and what is the pracAcal significance for • tendency to give up a proton or “pH” • relaAonship to uAlity as a buffering agent
TitraAon of a weak acid with a strong base
Preparing Buffers
• Choosing a Buffering Agent • Buffer preapraAon
PosiAon of TitraAon curve on the pH axis depends on the pKa of the Weak
Acid
Buffer
• 1: any of various devices or pieces of material for reducing shock or damage due to contact
• 2: a means or device used as a cushion against the shock of fluctuaAons in business or financial acAvity
• 3: something that serves as a protecAve barrier: as
• a. buffer state • b : a person who shields another especially from annoying rouAne maXers
hXp://www.merriam-‐webster.com/dicAonary/buffer
Buffer
• a substance capable in soluAon of neutralizing both acids and bases and thereby maintaining the original acidity or basicity of the soluAon; also : a solu(on containing such a substance
TitraAon Curves and Buffers
PolyproAc acids-‐MulAple Ionizing Groups
TitraAon of a PolyproAc Acid
hXp://2012books.lardbucket.org/books/principles-‐of-‐general-‐chemistry-‐v1.0m/s20-‐05-‐acid-‐base-‐AtraAons.html
CalculaAons with Phosphate Buffers
CalculaAons with Phosphate Buffers
IntroducAon to Amino Acids: A polyproAc acid