It shows how a buffer equilibrium shifts to minimize the change in hydronium ion concentration, and therefore pH, when an acid is added.

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0:00I will use equilibrium concept to explain how a buffer solution
0:06minimizes the change in pH when a small amount a bass and is that it
0:11we'll start off by considering a buffer solution
0:14in which the concentration of acidic acid Carafano idk acid
0:18and the concentration at the acetate RFN away Diane
0:22are both one dollar
0:25here's the equilibrium equation describing the buffer
0:29because this is an equally a solution any changes in the amount of water in
0:33this equilibrium
0:34are insignificant will discolor the water blue
0:38and we won't be concerned with it
0:40the concentration up I drone EM in this equilibrium
0:44is much lower done the one molar concentrations up a scenic acid and
0:48acetate
0:50now will construct grafts showing how the concentrations are the three species
0:54in the equilibrium
0:56will vary when we add an asset to this buffer and it really just
1:01this symbol shows that the yaxis on these graphs
1:04is actually much longer it then portrayed in this diagram
1:09the one molar concentrations at the Seediq acid an acid 8in
1:13are considerably higher than that the hydrazone in mine
1:17will draw lines on the grass showing the concentrations are three species
1:22before any acid is added
1:28noticed their con
1:29are all constant as we would expect an equilibrium
1:34at this point well at a small amount to the strong acid HCl
1:38to our buffer solution
1:41because HCl is an acid it produces H 30 plus signs
1:45in a solution
1:47the concentration at age 30 bias
1:50will quickly increase this shows as a vertical line on the graph
1:55the addition of HCl did not cause any instantaneous change in the
1:59concentration up to seek acid
2:02or in the concentration about city
2:05however this sudden increase in the concentration at age 30 class that just
2:09occurred
2:10is a stress to the equilibrium
2:13and because it's real class is a product this increase
2:16in its concentration will cause the equilibrium
2:20to shift to the left in order to compensate
2:24as this shift to the left occurs the concentration based 30 plus gradually
2:28goes down
2:31cuz the acetate diane is also a product
2:35its concentration also gradually goes down
2:40because the CD gas it is a reactant the shift to the left will cause its
2:45concentration to gradually increase
2:52after the shift to the left
2:53is complete a new equilibrium is established and as time goes on
2:58concentrations above all three species
3:01remain constant so the lines on the graphs become horizontal
3:06looking at the graph we can see that from the very beginning to the very end
3:10of the process
3:11concentration a pussy dick acid
3:14Joe Denette increase
3:16the concentration up the ass state I N showed a net decrease
3:22and we can see that from the very beginning to the very end
3:25the hydrazone a mine concentration showed a very small net increase
3:30this is because even though the hyde only in mind concentration showed a
3:34large net increase when HCl was first added
3:39its concentration partially decreased due to the buffering action that
3:43occurred
3:44as the equilibrium shifted to the left
3:47leaving us with a very small net increase instead of a large one
3:52now will retrace the changes in concentration up by drone %um
3:56when acid is added and the bar frequented p.m. just
4:00but this time in addition to that will consider the changes in pH
4:04as we go through the process
4:06will use a graph for pH boers is time to do that
4:10remember pH is defined as the negative blog at the hydrazone in mind
4:14concentration
4:16the negative sign means that as the hydrazone mine concentration goes up
4:20the pH goes down idoney mine concentration and pH
4:25have opposite trends
4:27I don't mind concentration and pH are different quantities
4:31so they have altogether different scales
4:34in our discussion well just examine qualitative changes
4:38in these two quantities
4:40their relative starting positions on the yaxis
4:43the graphs have no significance here
4:46before we at any acid the buffer solution is at equilibrium
4:50so the hydrazone mine concentration and pH
4:54both remain constant
4:57at this point will add a small amount to the strong acid HCl to our buffer
5:02solution