Chapter 14, Problem 27A

Interpretation Introduction

Interpretation:

An experimental method that is used to determine vapor pressure of a volatile liquid is to be described.

Concept introduction:

Volatile liquids evaporate readily from an open container. The molecules of liquid can escape the surface of liquid and form a gas. This process of evaporation needs energy to break the strong intermolecular forces in the liquid as compared to gases. The liquids with high vapor pressure are said to be volatile.

Answer to Problem 27A

Volatile liquid vaporized in open container when the vapor pressure equals the external pressure. Volatile liquids required low energy to escape the vapor phase.

Explanation of Solution

The vapor pressure of liquid at a given temperature is determined by the intermolecular forces that act among the molecule. Liquid with large intermolecular forces have relatively low vapor pressure, because such molecules need high energy to escape to the vapor phase. While liquid with small intermolecular forces (volatile liquid) have relatively high vapor pressure.

Barometer is used to measure the vapor pressure of volatile liquid. In case of volatile liquid, mercury level is pushed down. The change in the mercury level 9in milliliters) from its initial position (before the liquid was injected) to its final position it equal to the vapor pressure of the liquid.

Conclusion

Volatile liquid have higher vapor pressure while nonvolatile liquid have low vapor pressure.