Question

Isoelectric point is the pH at which colloidal particles :

• A. coagulate.
• B. becomes electrically neutral.
• C. can move toward either electrodes.
• D. none of the above.

Answer 1

Answer: (A), (B), (C)

coagulate.
becomes electrically neutral.
can move toward either electrodes.

The isoelectric point (pI, pH(I), IEP) is the pH at which a particular molecule carries no net electrical charge. The standard nomenclature to represent the isoelectric point is pH(I) although pI is also commonly seen and is used in this article for brevity.
The pI value can affect the solubility of a molecule at a given pH. Such molecules have minimum solubility in water or salt solutions at the pH that corresponds to their pI moves towards electrodes and often precipitate out of solution (coagulation).
Hence, options A, B and C are correct.