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Week 1

09/13/07

QuestionsAnswers
Q: Buffers, buffers, buffers. What is a buffer? A: A buffer is a mixture of a weak acid and its conjugate base or a weak base and its conjugate acid that cause a solution to resist changes in pH when an acid or base is added.
Q: How do buffers work? A: Buffer systems minimize pH changes by converting stronger acids and bases into weaker acids and bases.
Q: When are buffers most effective? A: Buffers are most effective when they're composed of equal amounts of weak acid and conjugate base. She also mention that you would want lots of each.
Q: What is meant by the following statement? The most effective buffering occurs in the portion of the titration curve that has a minimum slope. A: It means the most effective buffering occurs within 1 pH unit above and below the value of pKa.
Q: A buffer can only compensate for an influx or removal of hydrogen ions within approximately 1 pH unit of its _______. A: pKa.
Q: If the pH of a buffered solution changes from pKa to one unit below pKa, what happens to the concentration of [A-] to [HA]? A: It goes from 1:1 to 1:10.
Q: True or false? More concentrated buffers are more effective. A: True! They contain a greater total number of buffer molecules per unit volume and more is better.
Q: What does the Henderson-Hasselbalch equation describe? A: The Henderson-Hasselbalch equation describes the dissociation characteristics of weak acids and bases and the effect on pH.
Q: What is the Henderson-Hasselbalch equation? A: pH = pKa + log [A-]/[HA]
Q: If pH > pKa then _______ predominates. A: Base.
Q: If pH < pKa then _______ predominates. A: Acid.
Q: Name the four acid-buffer systems discussed in class. A: The hemoglobin (Hb) buffer system, the protein buffer system, the bicarbonate buffer system, and the phosphate buffer system.
Q: In class, what was referred to as the most important acid-buffer system? A: The bicarbonate buffer system, also called the carbonic acid-bicarbonate buffer system.
Q: What is the pH of a solution with a pKa of 3.86, [A-] of 1 molar, and [HA] of 10 molar? A: 2.86. Create your own variation of this question and work through them.
Q: Why can the bicarbonate buffer system work effectively at physiologic pH with a pKa of 6.1? A: Because C02 is a gas and can be exhaled by the lungs.
Q: The _______ buffer system is the only intracellular buffer system that can have an immediate effect on the pH of the extracellular fluid. A: The hemoglobin (Hb) buffer system.
Q: No question here, just a reminder to study the figures at the bottom of page 1-10 & the top of page 1-11. A: What are you looking here for? If there's no question, there's no answer. Go look at the figures.
Q: What is an aliphatic organic molecule? A: They are carbon strucures that are straight or branched, with single or double bonds, but DO NOT contain a ring.
Q: What is an aromatic organic molecule? A: They are carbon structures that contain cyclic structures, unsaturated.
Q: What is a hydrocarbon? A: Chains of carbon atoms.
Q: Did you know? Attaching other atoms or groups to the carbon backbone of a hydrocarbon forms all other organic molecules? A: Yah, I knew that too.
Q: Have you studies your functional groups lately? A: You might want to take a look at them again.
Q: _______ is determined by propotion of polar / nonpolar groups & their positions in the molecules. A: Solubility.
Q: What does the anagram OIL RIG stand for? A: It refers to oxidation/reduction and the loss or gain of electrons... Oxidation Is Loss, Reduction Is Gain.
Q:_______ has occurred if a molecule gains an oxygen atom or losses hydrogen (electrons). A: Oxidation.
Q: _______ has occured if a molecule loses an oxygen atom or gains hydrogen (electrons). A: Reduction.
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