Question

The colloid is:
A.Urea
B.Blood
C.Cane sugar
D.NaCl

Answer 1

To answer this question, you must recall the various types of colloids possible. Colloids are a type of mixtures in which the particle size is bigger than that in a true solution but smaller than that in a suspension. The solute remains dispersed in the solvent and does not settle down as precipitate.

Complete answer:
In option A, we have urea. Urea solution contains urea dissolved in water. In the solution, both urea and water are in the same phase forming a true solution and not a colloid.
In option B, we have blood. Blood is a natural body fluid that contains red blood cells, white blood cells and platelets dissolved in the plasma. The sizes of these cells, or solute in this case, lie in the range of 1 to 1000 nanometers.
In option C, Cane sugar is made up of the molecule sucrose.
In option D, NaCl is a crystalline ionic compound.

Thus, the correct answer is B.

Note:
Colloidal solutions are classified as multimolecular and macromolecular colloids on the basis of the properties of the sol particles. This classification is different from the one based on the interaction forces between the dispersed phase and the dispersion medium, i.e., lyophobic and lyophilic sols.
A multimolecular colloid is a type of colloid in which a large number of atoms or small sized molecules of a substance combine with each other in the dispersion medium forming aggregates whose sizes lie in the colloidal range.
Apart from multimolecular colloids, the other types of colloids under the same classification are macromolecular colloids. In these colloids, the substances form large molecules whose dimensions are similar to those of colloidal particles. These molecules have very large molecular masses and are thus known as macromolecules. When mixed in a suitable dispersion medium, these substances result in the formation of macromolecular colloids. They are different from multi molecular colloids as the particles are already large in size while in the latter, small particles aggregate to form large particles.