Which of the following is 'not' a colligative property ?

Options

A. Boiling point
B. Depression in freezing point
C. Elevation in boiling point
D. Osmotic pressure

Answer

To determine which of the following is 'not' a colligative property, we need to first identify what colligative properties are. Colligative properties are properties that depend on the number of solute particles in a solution, rather than the identity of the solute. The main colligative properties include:

1. **Elevation of boiling point**: This is the increase in the boiling point of a solvent when a solute is dissolved in it.
2. **Depression of freezing point**: This is the decrease in the freezing point of a solvent when a solute is added.
3. **Relative lowering of vapor pressure**: This refers to the decrease in vapor pressure of a solvent when a non-volatile solute is added.
4. **Osmotic pressure**: This is the pressure required to prevent the flow of solvent into a solution through a semipermeable membrane.

Now, let's analyze the options provided in the question:

1. **Boiling point elevation** - This is a colligative property.
2. **Freezing point depression** - This is also a colligative property.
3. **Relative lowering of vapor pressure** - This is a colligative property as well.
4. **Osmotic pressure** - This is a colligative property.

Since all the options listed are indeed colligative properties, we need to identify which one is not. However, based on the question, it seems there may be a misunderstanding or miscommunication in the options provided.

If we assume that one of the options was incorrectly stated or if there was a typographical error, we might conclude that the question is asking for a property that is not listed among the typical colligative properties.

**Conclusion**: Based on the standard definition of colligative properties, all the options given are colligative properties. Therefore, if we had to choose one that is 'not', we would need to clarify the options provided.

**Final Answer**: None of the options are 'not' a colligative property based on the standard definitions.