Henderson-Hasselbalch Approximation

Question 1

What is the Henderson-Hasselbalch equation?

Answer 1

pH=pKa+log([A-]/[HA])

Question 2

How is pKa related to Ka? What does Ka represent?

Answer 2

pKa=−log(Ka)

Acid dissociation constant; measures acid strength.

Question 3

What is buffering capacity and how does it work?

Answer 3

Ability to resist pH changes, typically one pH unit above and below the pKa

Question 4

How does a buffer compare to pure water when adding HCl?

Answer 4

Water: pH drops significantly

Buffer: pH drops slightly

Question 5

What limits the effectiveness of a buffer?

Answer 5

the concentration of its components

Question 6

How do buffers with multiple ionizable groups work? what does isoelectric charge mean?

Answer 6

pH more than 1 unit above pKa: Proton off (acid loses proton and becomes a conjugate base) ; pH more than 1 unit below pKa: Proton on (base gains proton and becomes a conjugate acid.

Isoelectric Point (pI): Average of pKa values where net charge is zero.