3.1 Buffers`
● Fundamentals of Buffers:
○ Definition:
■ A buffer is a mixture that resists changes in pH. It typically consists of a
weak acid and its conjugate base, or a weak base and its conjugate acid.
○ Function:
■ Buffers resist pH shifts when small amounts of strong acid or strong base
are added
○ Mechanism:
■ Adding Strong Acid (H3O+): The added acid reacts with the conjugate
base (A-) to form more weak acid (HA). This results in a slight decrease in
pH.
■ Adding Strong Base (OH-): The added base reacts with the weak acid
(HA) to form more conjugate base (A-). This results in a slight increase in
pH.
● Biological Significance: The blood buffer system
○ Composition:
■ Human blood utilizes a mixture of carbonic acid (H2CO3) and bicarbonate
anion (HCO3-)
○ Purpose
■ This system maintains blood pH between 7.35 and 7.45
○ Critical Limits:
■ Deviations above a pH of 7.8 or below 6.8 can lead to death
○ Clinical Context (Diabetes)
■ Insulin and glucagon regulate blood glucose levels via the liver and
pancreas
● Quantitative Analysis:
○ There are two primary ways to calculate the pH of a buffer
○ The ice table method
■ Write the equilibrium
■ Set up the Initial, change, equilibrium (ICE) table
■ Substitute equilibrium concentrations into the Ka expression and solve for
x (representing [H3O+].
■ Calculating pH =- log [H3O+]
○ Henderson- Hasselbach Equation
■
○ pH After Adding Acid or Base
■ Stoichometry:
● Calculate the moles of acid/base added and determine how they
consume/produce the buffer component (HA and A-)
■ Equilibrium
● Fundamentals of Buffers:
○ Definition:
■ A buffer is a mixture that resists changes in pH. It typically consists of a
weak acid and its conjugate base, or a weak base and its conjugate acid.
○ Function:
■ Buffers resist pH shifts when small amounts of strong acid or strong base
are added
○ Mechanism:
■ Adding Strong Acid (H3O+): The added acid reacts with the conjugate
base (A-) to form more weak acid (HA). This results in a slight decrease in
pH.
■ Adding Strong Base (OH-): The added base reacts with the weak acid
(HA) to form more conjugate base (A-). This results in a slight increase in
pH.
● Biological Significance: The blood buffer system
○ Composition:
■ Human blood utilizes a mixture of carbonic acid (H2CO3) and bicarbonate
anion (HCO3-)
○ Purpose
■ This system maintains blood pH between 7.35 and 7.45
○ Critical Limits:
■ Deviations above a pH of 7.8 or below 6.8 can lead to death
○ Clinical Context (Diabetes)
■ Insulin and glucagon regulate blood glucose levels via the liver and
pancreas
● Quantitative Analysis:
○ There are two primary ways to calculate the pH of a buffer
○ The ice table method
■ Write the equilibrium
■ Set up the Initial, change, equilibrium (ICE) table
■ Substitute equilibrium concentrations into the Ka expression and solve for
x (representing [H3O+].
■ Calculating pH =- log [H3O+]
○ Henderson- Hasselbach Equation
■
○ pH After Adding Acid or Base
■ Stoichometry:
● Calculate the moles of acid/base added and determine how they
consume/produce the buffer component (HA and A-)
■ Equilibrium
