In the following relationships, Q stands for quinine and QH + for its protonated form?

Question

a) [ Q ] = [ QH + ]


b) [ Q ] > [ QH + ]


c) [ QH + ] > [ Q ]



Using the letters for the above relationships identify the dominant quinine species for each of the following steps of the above titraion.



I. At the start of the titration



II. At the halfway-point



III. At the equivalence point

Answer 1

I.- At the start of titration:

[Q ] > [ QH + ]

II.- At the halfway-point:

[ Q ] = [ QH + ]

III.- At the equivalence - point:

[ QH + ] > [ Q ]

Answer 2

I. b
II. c
III. a

at the start you have a lot more Q as you add acid it becomes protonated, but at the half point you have an overshoot until it becomes equilibrized so you technically have more protonated Qs and at equilibrium its obviously equal.