Question

Which of the following forms a colloidal solution in water?
A: $ NaCl $
B: Glucose
C: Starch
D: Barium nitrate

Answer 1

Hint :Colloidal suspension basically refers to a solution where the size of solute particles is considered to be intermediate between that of the true solution and suspension. For example: milk, mayonnaise, butter, muddy water, gelatin, etc.

Complete Step By Step Answer:
All colloidal solutions possess the following properties:
(i) Colloidal solutions are heterogeneous in nature and consist of the two phases i.e. dispersed phase and dispersion medium.
(ii) Colloidal solutions are stable as their particles do not settle down and are in a state of motion.
(iii) Colloidal particles can be passed through ordinary filter papers and can only be retained through ultra-filters.
(iv) The number of particles in a colloid solution will be very small in comparison to the true solution.
(v) The dispersed particles in a colloid solution scatter light thus they exhibit Tyndall effect.
Now if we look at the options, it is clear that Starch in water exhibits all of these colloidal solution properties. While $ NaCl $ and Barium nitrate form a true solution in water while Glucose in water does not exhibit Tyndall effect.
As a result, Starch forms a colloidal solution in water. Hence, the correct answer is Option C.

Note :
 There are four types of colloids including sol (solid particles in a liquid), emulsion (between the two liquids), foam (gas particles in either a liquid or a solid), and aerosol (liquid or the solid particles in a gas). Thus, it means that clouds can fall under the category of aerosol colloids including a suspension of water droplets (i.e. water vapour) or small particulate matter (i.e. ice crystals) in a gas.