acids, bases, and buffers OH MY!!

Question 1

Describe the law of mass action.

Answer 1

Keq= [products]/[reactants].

Question 2

Define pH and pKa.

Answer 2

The strength of an acid or base is a measure of its propensity to either donate or accept protons measured as its pKa. pKa= -logKa.
In chemistry, pH is a measure of the acidity or basicity of a solution.
pH= -log [H]

Question 3

Write the Henderson-Hasselbalch (H-H) equation for any given weak acid or base.

Answer 3

google it

At 50% dissociation, pH=pKA

Question 4

Define the H-H equation for the bicarbonate buffer system in extracellular fluid and use it to
evaluate clinical lab data.

Answer 4

pH = 6.1 + log [HCO3-]mM/ .03*Pco2mmHg

When you get measurements of blood gases, will receive partial pressures in mmHg.

Question 5

Define normal blood pH, [HCO3-] and pCO2.

Answer 5

Blood pH: Arterial: 7.34- 7.44, Venous 7.28-7.42
[HCO3-]: 24mM
pCO2: 40 mmHg, or 40*.03= 1.2mM
Ratio of HCO3- to CO2 is 20, gives pH of 7.4 in HH

Question 6

Describe how weak acids and bases work to buffer pH and define the pH range of maximal
buffering capacity.

Answer 6

Effective buffering occurs in the range from [A-]/[HA] = 0.1 to 10 or within one pH unit on either side of the pKa. Weak acids and bases interact in a given range to control pH.

Question 7

Use the H-H equation to solve problems of how pH changes in defined buffers i.e. you
should be able to determine how many equivalents of acid or base are needed to titrate the ionizable groups(s) of a weak acid or base from a starting pH to a final pH, given its concentration and pKa.

Answer 7

Practice problems here