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Buffer Solution in Action – Acid-Base Reactions

by Adam Le Gresley, PhD
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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.


    About the Lecture

    The lecture Buffer Solution in Action – Acid-Base Reactions by Adam Le Gresley, PhD is from the course Ionic Chemistry.


    Included Quiz Questions

    1. 5.70
    2. 4.34
    3. 4.74
    4. 5.04
    5. 7.40
    1. During buffer neutralization one component gets converted into the other
    2. It prevents the pH changes via breakdown of acid component of the buffer system till its last molecule
    3. It prevents the pH changes via breakdown of conjugate base component of the buffer system till its last molecule
    4. It prevents the pH changes via breakdown of base component of the buffer system till its last molecule
    5. It prevents the pH changes via breakdown of conjugate acid component of the buffer system till its last molecule
    1. It is a complex derivation dealing with redox reactions
    2. It assumes that the equilibrium concentrations are same as the concentrations of the components mixed in the buffer preparation
    3. The ratio of the concentration of conjugate base to that of weak acid should be between 0.10 and 10.00
    4. The concentrations of components should exceed Ka by at least 100 times
    5. pH = pKa + {(log of conjugate base concentration)/ (log of weak acid concentration )}
    1. pH = pKa + log ([CH3COO-] / [CH3COOH])
    2. pH = pKa + log ([CH3COOH] / [CH3COO-])
    3. pKa = pH + log ([CH3COO-] / [CH3COOH])
    4. pKa = pH + log ([CH3COOH] / [CH3COO-])
    5. pH = pKa - log ([CH3COO-] / [CH3COOH])

    Author of lecture Buffer Solution in Action – Acid-Base Reactions

     Adam Le Gresley, PhD

    Adam Le Gresley, PhD


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