At room temperature, write the ascending order of volatility and vapour pressres of (A) water, (B) hexane and (C ) ethanol. Explain the reasons.

Answer

To determine the ascending order of volatility and vapor pressures of water (A), hexane (B), and ethanol (C) at room temperature, we need to analyze the intermolecular forces present in each substance.

### Step-by-step Solution:

1. **Understanding Volatility and Vapor Pressure**:
- Volatility refers to how readily a substance vaporizes. Higher volatility means a substance will evaporate more quickly.
- Vapor pressure is the pressure exerted by a vapor in equilibrium with its liquid phase. Higher vapor pressure indicates higher volatility.

2. **Analyzing Water (A)**:
- Water has extensive hydrogen bonding due to its polar nature. This strong intermolecular force requires more energy to break, resulting in lower volatility and lower vapor pressure compared to substances with weaker intermolecular forces.

3. **Analyzing Ethanol (C)**:
- Ethanol also exhibits hydrogen bonding, but it is less extensive than that in water. This means that while ethanol is still relatively less volatile than substances with weak intermolecular forces, it is more volatile than water due to its weaker hydrogen bonding.

4. **Analyzing Hexane (B)**:
- Hexane is a non-polar molecule and does not form hydrogen bonds. Instead, it experiences only weak Van der Waals forces (London dispersion forces). As a result, hexane is the most volatile of the three substances, with the highest vapor pressure.

5. **Arranging in Ascending Order**:
- Based on the analysis, we can arrange the substances in ascending order of volatility and vapor pressure:
- Water (A) < Ethanol (C) < Hexane (B)

### Final Answer:
The ascending order of volatility and vapor pressures is:
**Water (A) < Ethanol (C) < Hexane (B)**