Question

At iso-electric point:
A.Conc of cation is equal to conc of anion
B.Net charge is zero
C.Maximum conc. of di-polar ion (zwitterion) will be present
D.All of the above

Answer 1

Hint: So, for this question we should first understand the features of isoelectric point $\,pI\,$. Iso-electric point is the point which is interrelated to $\,pH\,$. This term mainly comes under the topic of electrophoresis

Complete step by step answer:
Let us first understand the isoelectric point;
The $\,pH\,$ at which a molecule does not bear a net electrical charge or is electrically neutral is the isoelectric point. Now, another term related to this topic is zwitterion. So zwitterion is basically a molecule of at least two functional groups: one with a positive charge and the other with a negative charge, with a zero as total charge.
So, in order to make the charge zero, the total number of cations and anions must be equal. Hence option A is correct.
From the above explanation it is clear that the charge is zero in an isoelectric point and hence option B is also correct.
As the electric charge is neutral the concentration of zwitterion form will also be more in this point because at isoelectric point both positive and negative form of a substance exist and zwitterion is one such and hence option C is also correct.

Hence, option D is the correct answer as all the above options are correct.

Note:
The $\,pI\,$ value at a given $\,pH\,$ will influence a molecule's solubility. These molecules have minimum solubility at the pH corresponding to their $\,pI\,$ in water or salt solutions and frequently precipitate out of the solution. The surface of the protein is primarily negatively charged at solution $\,pH\,$ that is above $\,pI\,$, and hence repulsive forces can be exhibited by like-charged molecules.