Vapor Pressure & Boiling (2024)

FAQs

What is the relationship between boiling and vapor pressure? ›

The relationship between the vapour pressure and boiling point is that both are inversely proportional. The more volatile liquid evaporates fast as compared to the less volatile liquid at a low temperature because the volume increases with respect to temperature so it has a low boiling point.

We can say that the boiling point increases as the vapour pressure decreases or vice versa. - It is found that if the intermolecular forces are strong then the molecules will be strongly attracted to each other, and the vapour pressure will be low and a large amount of energy will be added to separate the molecules.

Lowering the vapor pressure of a substance has an obvious effect on boiling point; the boiling point goes up. The BP increases because more energy is required for the solvent's vapor pressure to reach the external pressure.

Boiling Points. As the temperature of a liquid increases, the vapor pressure of the liquid increases until it equals the external pressure, or the atmospheric pressure in the case of an open container. Bubbles of vapor begin to form throughout the liquid, and the liquid begins to boil.

Boiling point is the temperature at which vapor pressure exerted by molecules equals atmospheric pressure present on the surface of liquid. Boiling point is the temperature at which vapour pressure exerted by molecules equals atmospheric pressure present on the surface of liquid.

As the pressure applied to the liquid surface is increased, the energy needed for the liquid molecules to expand to gas phase also increases. Hence, a higher temperature is required to change liquid to gas phase. So, boiling point of liquid rises on increasing pressure.

Generally a substance's vapor pressure increases as temperature increases and decreases as temperature decreases (i.e. vapor pressure is directly proportional to temperature).

The melting points of most of the solid substances increase with an increase of pressure acting on them. However, ice melts at a temperature lower than its usual melting point, when the pressure increases.

The vapor pressure of a liquid varies with its temperature, as the following graph shows for water. The line on the graph shows the boiling temperature for water. As the temperature of a liquid or solid increases its vapor pressure also increases. Conversely, vapor pressure decreases as the temperature decreases.

Vapour pressure is a measure of the tendency of a material to change into the gaseous or vapour state, and it increases with temperature. The temperature at which the vapour pressure at the surface of a liquid becomes equal to the pressure exerted by the surroundings is called the boiling point of the liquid.

What is the relationship between evaporation and boiling point? ›

Explanation: Boiling point and evaporation have an inverse relationship, that is, the higher the boiling point of a substance, the lower is the rate of its transformation from liquid to gas (or evaporation).

The greater the pressure it exerts, the weaker the intermolecular forces between molecules in its liquid state; the more volatile the liquid; the lower the boiling point and the faster its evaporation rate. Vapor pressure is an indication of a liquid's evaporation rate.

Thus at room temperature, the substance with the lowest boiling point will have the highest vapor pressure (easiest to get into the gas phase). The substance with the highest boiling point will have the lowest vapor pressure. Vapor pressure is a liquid property related to evaporation.

Vapour pressure is a measure of the ability of a compound to bond with itself; compound molecules that bond well with each other will have a low vapour pressure (less tendency to escape to the vapour phase), while poorly bonding compounds will have a high vapour pressure.

Thus at room temperature, the substance with the lowest boiling point will have the highest vapor pressure (easiest to get into the gas phase). The substance with the highest boiling point will have the lowest vapor pressure. Vapor pressure is a liquid property related to evaporation.

Vapor Pressure and Intermolecular Forces

Substances with strong intermolecular forces will have lower vapor pressure, because fewer molecules will have enough kinetic energy to escape at a given temperature. Substances with high vapor pressures are said to be volatile - that is, they easily evaporate.

At the normal boiling point of a liquid, the vapor pressure is equal to the standard atmospheric pressure defined as 1 atmosphere, 760 Torr, 101.325 kPa, or 14.69595 psi.