Question

How much molecular mass of nacl is obtained experimentally using colligative properties?

Answer 1

Anyone who lives in a cold place, like I do, knows the danger of icy roads and sidewalks. To stop cars and people from slipping around, the roads are often treated with a salt. The salt melts the ice and makes the roads and sidewalks much safer. Have you ever wondered why?

The salt has dissolved in the ice and created a solution of icy slush. The salt is a solute that has affected the property of the pure solvent. This property is a colligative property. A colligative property is a property that depends on the number of solute particles present, but not on the type of particle. In other words, the more solute particles in the solution, the greater the effect. Don't worry if this doesn't make much sense now; we will look at this more in the next part of the lesson.

Colligative properties include:

Vapor pressure lowering

Boiling point elevation

Freezing point depression

Osmotic Pressure

In this lesson, we will focus on freezing point depression and see how it can be used to calculate the molar mass of an unknown substance.

Answer 2

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As concentration of particles in the solution is doubled, value if colligative property is double than expected value and hence molecular mass is halved, i.e., observed molecular mass = 58.5/2 = 29.25