Question

Which of the following is/are negatively charged sol?
A.Gold sol
B.Prussian blue dye
C.Haemoglobin
D.Starch

Answer 1

To answer this question, recall the definition of colloids. A colloidal solution is defined as a homogeneous and a non-crystalline substance, in which large molecules of one substance are dispersed through a second substance.

Complete step by step answer:
- The particles of a colloid are always in a constant set of motion and do not settle due to continuous collisions. These cannot be separated by ordinary filtering or centrifuging like those in a suspension. A colloid is different from a solution as in a solution, solute and solvent are a part of single-phase, whereas in a colloid the dispersed phase and a continuous phase are part of different phases and separated by phase separation.
- The dispersed-phase particles are generally visible in an optical microscope. Colloids also show the property of the Tyndall effect which is defined as the scattering of light by particles in the colloid. The substances which are dispersed in the solution are called the dispersed phase, and the solution in which it is dispersed is called dispersion medium.
- The sol particles acquire positive or negative charge by preferential adsorption of positive or negative ions. When two or more ions are present in the dispersion medium, usually preferential adsorption of the ion common to the colloidal particle takes place. Positively charged sols are mostly metal hydroxides whereas negatively charged sols are metal sols or metal sulphide sols. Gold sol and starch sol are examples which are negatively charged.

Hence, the correct answer to this question is option A and D.

Note:
You should know the difference between sol, solution and suspension.
- Solution: A solution is a homogeneous mixture of two or more substances stable in nature.
- Sol: A sol is a heterogeneous mixture. They are quite stable.
- Suspension: These are a heterogeneous mixture unstable in nature.