Acids, Bases, and Buffers Flashcards Preview

M2M Unit III > Acids, Bases, and Buffers > Flashcards

Flashcards in Acids, Bases, and Buffers Deck (11):
1

Law of Mass Action

Rate of rxn is partially determined by concentrations of reactants and products in addition to the equilibrium constant.
If product or reactant concentrations greatly increase, the rxn will move in other direction
K=Kf/Kr=[R1][R2]/[P1][P2]

2

Define pH

Concentration of H+ in solution, measured -log[H]. Given that Keq of water is 1.8*10^-16, [H][OH]=1*10^-14 so pH + pOH =14

3

Define pKa

pKa=-log(Ka)=-log([H+][A-]/[HA])
This is the acid dissociation constant, gives the strength of the acid, lower pKa means less acid is bound at equilibrium so the acid is stronger.

4

Henderson Hasselbach Equation

pH=pKa+log([A-]/[HA])
So pH=pKa at 50% dissociation

5

Bicarbonate Buffer System H-H equation

Bicarb buffer system regulates physiologic pH by taking up extra protons or hydroxyls without drastically changing the pH. This is an open system helped by CO2 exchange and bicarbonate excretion.

pH=6.1+log([HCO3-]mM/(0.3*PCO2mmHg)

6

Normal Blood pH

Arterial: 7.34-7.44
Venous: 7.28-7.42

7

Normal Bicarbonate Concentration

[HCO3-] 24mM

8

Normal PCO2

40mmHg

9

Why do weak acids make good buffers? What is maximal pH range for buffers?

Weak acids are good buffers because they are only partially associated at physiologic pH, meaning there is undissociated acid and conjugate base to take up extra H or OH.
Buffers work best within 1 pH (0.1 to 10 [A-]/[HA]) of pKa because acid is 50% dissociated when pH=pKa

10

Acid Base Problems

See Handout

11

Important Weak Bases

Purines, Pyrimidines, amphetamines, procianamide, nortriptylene, local anesthetics