Van Hoff factor

Describe the Van’t Hoff Factor?

The Van’t Hoff factor showcases how solutes influence the solutions’ colligative characteristics. The particles’ concentration ratio is generated when the material gets mixed with the substance’s concentration by mass, known as the Van’t Hoff factor.

When a specific non-electrolytic chemical dissolves into the water, the Van’t hoff constant value is normally 1. Whereas the I’s value equals the total ions available in an ionic molecule’s single formula unit at the time it creates a solution in water.

We can take CaC2 as an example. It contains an optimum Van’t Hoff factor of about 3 as it gets dissociated into two different Cl– ions and one Ca2+ ion. However, a few such ions inside the solution form associations among them. Further, it results in an overall reduction in the solution of the particles.

The factor is named after Jacobus Henricus Van’t Hoff, a Dutch physical scientist who earned the 1st Nobel Prize in chemistry. For electrolytic solutions, it is worth noting that the witnessed Van’t Hoff factor is generally lesser than the expected value (because of the ion-pairing). The ion with a higher charge gets the higher divergence.

Impact of Association and Dissociation

• Combining 2 or more particles to create a single entity is known as an association.

• When carboxylic acids dissolve in benzene, they dimerise, an example of two interacting particles.

• A molecule splitting into several ionic entities is referred to as dissociation.

• When sodium chloride (NaCl) is dissolved in water, it splits into Na+ & Cl– ions.

The following table shows the consequences of a solute’s association/dissociation regarding the solution, the Van’t Hoff factor, and its colligative characteristics.

• The molar mass exceeds the expected value.

• The molar mass is lower than the expected value.

• The Van’t Hoff factor has a value of less than one.

• It has a value larger than one.

• The colligative qualities have lower values than predicted. Reduced boiling and freezing points, for example.

• Colligative qualities have been proven to have higher values. High osmotic pressure and the boiling point, for example.

Abnormal Molar Masses

When computed from colligative characteristics of solutions, the theoretical estimates of the molecular mass are occasionally found to deviate from the empirically measured values. Abnormal molar masses are a term used to describe these readings.

When solutes given in the solution are dissolved in the given solvent, they will dissociate into numerous ions, according to Van’t Hoff. Since the quantity of the solute particles solely determines colligative characteristics, the breakdown of the solute molecules in the ions grows in the number of the particles and hence impacts the colligative capabilities.

If all the molecules of NaCl dissociate in water when a single mole of the NaCl is dissolved in 1 kg of water, the resulting solution will include a single mole of chlorine, Cl– ions and on the other hand, 1 mole of the Na+ ions. However, when utilising the colligative characteristics to calculate the molar mass, we simply consider the presence of 1 mol of NaCl in the solution.

In an aqueous condition, some chemicals tend to associate, and the given number of ions/molecules in the solution is lower than the actual given number of the molecules for such molecules. As a result, the apparent molar mass of the component will always be smaller than the true mass for those compounds that dissociate in a solution. The true mass of compounds associated with solutions is always smaller than the reported molar mass.

The abnormality of the given molecular mass can be easily explained out there:

• The number of particles increases due to the dissociation of solute molecules into numerous ions. As a result, the solution’s colligative qualities improve.

• Also, because molar mass cannot be reversed related to colligative characteristics, it has a smaller value than one may predict.

• The total particles in a solution drop when the solute particles connect, resulting in a certain decrease in colligative characteristics.

• The molar mass found in this example is greater than predicted.

Calculation of Van’t Hoff factor

It can be calculated by using the following formula :

i = apparent number of particles in solution/number of moles of solute dissolved

Conclusion

The Van’t Hoff’s factor takes into account osmotic pressure, a relative reduction of vapour pressure, boiling point elevation, and freezing point depression. The Van’t Hoff factor is defined as the relationship between the actual concentration of particles created when a substance is dissolved and the calculated concentration of a substance based on the mass of the material.