00:01
To answer your question number seven, i've recreated your graph in this drawing.
00:05
And the equivalence point here noted in green, it occurs according to your previous answer, at about ph 8 .73, right? and that also corresponds with a certain volume down here, which is probably estimating it looks like maybe 25 .5 miller.
00:32
Of base.
00:34
Okay.
00:36
Now we also have this equation, this relationship for the equilibrium constant ka for the dissociation of a weak acid, and that is given as ka is equal to the concentration of our conjugate base a minus times the h3o plus the hydronium ion all over the concentration of the original acid, ha.
01:11
Okay.
01:12
Now, a special thing happens halfway to the equivalence point, a minus will equal ha.
01:20
So that means whatever value a minus is, ha will have the same value.
01:25
So any number over itself is equal to one, and those cancel out, which would give us the expression, k -a is just equal to the concentration of hydronium -i.
01:36
Now, another thing we can do is take the negative log of each side of this equation.
01:41
If we take the negative log of ka, we call that p -k -a.
01:46
And if we take the negative log of hydronium concentration, we call that the ph, right? so at this special time when the concentration of a -minus equals h -a, then this would be true p -k -a equals the ph...