Why does boiling point decrease with the vapour pressure? (2024)

FAQs

Why does boiling point decrease with the vapour pressure? ›

If the intermolecular interactions are weak, the liquid will have a high vapour pressure and require minimal energy to separate the molecules. As a result, the boiling point will be quite low. As a result, we can deduce that vapour pressure and boiling point are inversely related.

The vapor pressure of a liquid lowers the amount of pressure exerted on the liquid by the atmosphere . As a result, liquids with high vapor pressures have lower boiling points.

The boiling point decreases with a decrease in pressure. It is because lower the pressure applied on the surface of the liquid, lower is the energy required to expand the liquid molecules into the gas phase. Hence, a lower temperature is needed to change liquid into gas.

When the vapor pressure increases enough to equal the external atmospheric pressure, the liquid reaches its boiling point. The boiling point of a liquid is the temperature at which its equilibrium vapor pressure is equal to the pressure exerted on the liquid by its gaseous surroundings.

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.

When a non-volatile solute is added to a solvent, the vapour pressure of the resulting solution is lower than that of the pure solvent. Therefore, a greater amount of heat must be supplied to the solution for it to boil. This increase in the boiling point of the solution is the boiling point elevation.

The decrease in the vapor pressure of the solvent that occurs when a solute is added to the solvent causes an increase in the boiling point and decrease in the melting point of the solution. According to this figure, the solution can't boil at the same temperature as the pure solvent.

The proportion of solvent molecules that escape into the vapor phase decreases, lowering the pressure produced by the vapor phase. This is referred to as relative vapor pressure reduction.

The melting point of ice decreases when pressure increases because when pressure is increased volume is decreased and the volume of water is less than ice. So it will be easier to change the state from solid to liquid, and therefore, the melting point decreases.

When compared to the pressure at sea level, the air pressure at high elevations is quite low. Cooking at a high elevation differs from cooking at sea level. As a result, water at high elevations boils at a lower temperature. It takes less energy to raise water to the boiling point when air pressure is lower.

Why are boiling point and vapor pressure inversely related? ›

- Whereas, if the intermolecular forces are weak, then liquid will have high vapour pressure, little amount of energy will be added to separate the molecules. And hence the boiling point will be low. - Hence, we can say that vapour pressure and boiling point are inversely proportional to each other.

As the gas bubble forms within the liquid, the vapour pressure within the bubble must be equal to atmospheric pressure to escape the surface, at which point the liquid boils.

The boiling point of liquid increases with increase in pressure.

As branching increases, the surface area of the molecule decreases which results in a small area of contact. As a result, the Van der Waals force also decreases which can be overcome at a relatively lower temperature. Hence, the boiling point of an alkane chain decreases with an increase in branching.

As the temperature of a liquid or solid increases its vapor pressure also increases. Conversely, vapor pressure decreases as the temperature decreases.

As the gas bubble forms within the liquid, the vapour pressure within the bubble must be equal to atmospheric pressure to escape the surface, at which point the liquid boils.

Water has a great propensity to hydrogen-bond because of the polarity of the O−H bond, and these hydrogen bonds, which act intermolecularly (i.e. BETWEEN molecules), account for the unusually high boiling point.

When a non-volatile solute is added to a volatile liquid solvent, the solution vapour pressure will be lower than that of the pure solvent. As a result, the solid will reach equilibrium with the solution at a lower temperature than with the pure solvent.