Question

Which of the following is not correct about colloids?

• A. The $pH$ at which colloid particles do not carry charge is called isoelectric point of colloid.
• B. At isoelectric point, colloidal state possess minimum stability.
• C. At isoelectric point, sol particles possess no electrophoretic motion.
• D. Silicic acid sol have minimum stability at its isoelectric point.

Answer 1

The correct option is D Silicic acid sol have minimum stability at its isoelectric point.

The isoelectric point (pI) is the pH at which a particular molecule or surface carries no net electrical charge. Amphoteric molecules called zwitter ions contain both positive and negative charges depending on the functional groups present in the molecule.

In electrophoresis there is no motion of the particles in an electric field at the isoelectric point.

The stability of colloid becomes minimum at the iso-electric point but as an exception, silicic acid has been found to have maximum stability at the isoelectric point.