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Buffer Solutions – Acid-Base Reactions
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Slides 01 Chemistry Advanced Le Gresley.pdf
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00:00 Right. So, let’s talk about buffer solutions. Buffer solutions are specific recipes that contain either a weak acid and its conjugate base or a weak base and its conjugate acid. 00:15 This is very important because what we are using or what we are doing is we’re making sure that we can control to some extent what happens when we add subsequent amounts of base and subsequent amounts of acid. We cannot do this, if we deal with a strong acid or strong base since dissociation occurs in both cases almost completely. 00:38 Buffers have the property of being able to oppose changes in pH despite the addition of acid base. So, in this case, what it means is that, if you like, for example, were to look at a biological fluid, let’s say, for the sake of argument, blood, the idea that minute changes in acid concentration would be allowable would be to effectively stop a lot of the proteins from being able to work. Stopping proteins from work would soon lead to death pretty much. And so, therefore, we need to have our own buffers from a biological perspective in order to oppose any minute changes in the concentrations of acids in our bodies through a whole host of different media. 01:21 Buffer solutions are important not just in maintaining experimental setups, but also in terms of maintaining the integrity and pH of chemical and biological setups. Studies involving proteins always required buffer solutions to preserve their structures since, as you can appreciate, most proteins are actually quite intolerant to variation in acidity. 01:42 Changes in acidity actually can result in changes in tertiary and quaternary structures to these proteins and render them non-functional. 01:49 Enzymes, in particular, are often highly sensitive to changes in pH. And indeed one of the ways in which proteins can be denatured i.e. enzymes can be stopped doing what they do, is by treating them to an acid and heat bath. 02:07 Buffers can also help to preserve drugs in solutions for periods of time by present... 02:14 preventing acid or base degradation. 02:17 Water itself has no buffering capacity. Pure water has a pH of 7, as we said before. 02:25 And 1.0 litres or 1 litre of water plus a tiny amount of hydroxide ion has a pH of 12.3. 02:35 When we do the same with acid, let’s say 0.02 mol of hydrochloric acid, this would result in the formation of a solution with a pH of 1.7. So, water is easily changed in terms of its concentration of available [H+] by virtue of minute changes in the concentrations of free acid and free base that are provided. A buffered solution would be able to maintain its pH within a few hundredths of a pH unit after the addition of similar amounts of acid or base. And that’s the desire when it comes to a good buffer. 03:10 Buffer solutions, a common buffer solution, which is relatively easy to explain and easy
About the Lecture
The lecture Buffer Solutions – Acid-Base Reactions by Adam Le Gresley, PhD is from the course Ionic Chemistry.
Included Quiz Questions
Which of the following statements about buffer solutions is not true?
- A buffer solution does not have hydrolytic and enzymatic stabilities.
- It has a limited effect on biochemical or chemical reactions.
- It exhibits minimum changes in the pH due to a change in temperature.
- A buffer consists of a mixture of either a weak acid and its conjugate base, or a weak base and its conjugate acid in water.
- A buffer solution resists changes in the pH upon addition of small amounts of an acid or a base to the solution.
Which of the following is NOT a correct application of a buffer?
- A citric acid buffer acts as an antiseptic agent due to its highly acidic nature.
- Buffers help in the preservation of drugs in solution forms from acidic or basic degradations.
- During experimental studies, buffer systems help in biochemical assays and cell culturing techniques.
- Buffers prevent the product spoilage during brewing processes in the fermentation industry.
- Body and baby lotions are buffered with slightly acidic buffer solutions to stop bacteria growth in them.
Why does water not have buffering properties?
- It cannot prevent the changes in the pH due to additions of free acid or free base even in minute quantities.
- It can prevent the variations in the pH due to additions of free acid even in minute amounts.
- It can prevent the alterations in the pH due to additions of free base even in minute dosages.
- Water changes the molecular structure of the acid or base added to it.
- Water starts the polymerization reaction between acid or base molecules.
Why is phosphate-buffered saline (PBS) commonly used in biological research?
- It mimics the natural pH and salt concentrations of the plasma or biological systems and helps in maintaining the osmotic balance between the external and internal environments of a living tissue or cell.
- It can be prepared easily by mixing the components in any quantities under unsterilized conditions.
- It is a hypertonic solution, hence it helps in the extraction of cellular components without cell wall or plasma membrane breakage.
- It is a hypotonic solution, hence it is quite helpful in transporting large quantities of the test compounds inside a cell.
- It is toxic to many bacteria and fungi, thus it helps in the prevention of infections during cell culturing techniques.
Author of lecture Buffer Solutions – Acid-Base Reactions
Adam Le Gresley, PhD
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Very complete and straight to the point, better than when my teacher explains
