Question

The Van’t Hoff factor for a dilute aqueous solution of glucose is:

A.) Zero

B.) 1.0

C.) 1.5

D.) 2.0

Answer 1

Van’t Hoff factor is actually the ratio between the actual concentration of particles produced upon dissolution and the concentration of substance before dissolution. For non-electrolytes, the van’t Hoff factor is unity (1).

Complete answer:

The van 't Hoff factor is a measure of the effect of a solute on colligative properties such as osmotic pressure, boiling-point elevation, relative lowering in vapor pressure and freezing-point depression. It is denoted by ‘i’. It is actually the ratio between the actual concentration of particles produced upon dissolution and the concentration of substance before dissolution.

For most ionic compounds, when they are dissolved in water, the van’t Hoff factor is equal to the total number of discrete ions produced by the substance. For most non-ionic compounds, the van’t Hoff factor is 1 as no other ion is produced by them upon dissolution. This is true for ideal solutions only, as occasionally ion pairing occurs in solution. At any time, a small number of ions pair with each other and are counted as a single particle. Due to this reason, the van’t Hoff factor is less than what predicted in an ideal solution.

As glucose is a non-ionic compound, it doesn’t break down further to give any ions in the solution. Hence, the van’t Hoff factor for a dilute aqueous solution of glucose is one (1).

Therefore, the correct answer is (B) 1.0.

Note: Remember that the van’t Hoff factor for a substance can be less than one as well. This is possible when the ions of a substance dissolved in a solution come together or associate with each other.