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

Question

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


a) [ QH + ] > [ Q ]


b) [ Q ] > [ QH + ]


c) [ Q ] = [ QH + ]


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

Quinine is (2-ethenyl-4-aza bicyclo[2.2.2]oct-5-yl)- (6-methoxyquinolin-4-yl)-methanol.

You neglected to specify whether or not you were titrating the Quinine with an acid or the protonated form with a base. The results will be almost opposite depending upon the reaction.

Assuming that the reaction is

Q + H+ --> QH+

I.) At the start b) is true: [ Q ] > [ QH+ ]
II.) At the halfway-point c) is true: [ Q ] = [ QH+ ]
III. At the equivalence point a) is true: [ QH+ ] > [ Q ]