Vapor Pressure: Molecular Size (2024)

FAQs

How does molecular size affect vapor pressure? ›

Generally with increase in molecular weight of molecule boiling point increase and hence volatility decreases which result in low vapor pressure.

The bigger the molecule is and the more electrons it has, the bigger the London forces are. Bigger molecules usually have larger molecular weights; hence the correlation of vapor pressure with molecular weight.

Do larger or smaller molecules have a higher vapor pressure? Larger molecules are more difficult to bring into the gaseous phase, so large molecules have a smaller vapor pressure than small molecules.

Types of Molecules: the types of molecules that make up a solid or liquid determine its vapor pressure. If the intermolecular forces between molecules are: relatively strong, the vapor pressure will be relatively low. relatively weak, the vapor pressure will be relatively high.

From the equation, we can see that, all else held equal, if b increases (i.e. the molecule size increases) then the pressure goes up.

Smaller molecules tend to diffuse faster than larger molecules. Molecules diffuse faster in a fluid with a lower viscosity, like water, than in a fluid with a higher viscosity, like syrup.

The vapour pressure of a liquid is the pressure exerted by the molecule that leaves the liquid surface of the walls of the container. This vapour pressure is controlled or affected by certain factors. These factors include the nature of liquid, temperature, boiling point of the liquid, and solute concentration.

As the temperature of water increases vapour pressure of water also increases and as the temperature decreases the vapour pressure of the water also decreases. The vapour pressure of the water does not depend on the volume of the container and surface area of the container.

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

Temperature: The vapour pressure of a liquid increases with increasing temperature. This is because as the temperature increases, the kinetic energy of the molecules also increases. This allows more molecules to overcome the intermolecular forces and escape into the vapour phase, thereby increasing the vapour pressure.

What does the vapor pressure depend on? ›

The liquid's vapour pressure depends on the nature of the fluid and temperature, with an increase of intermolecular force of attraction Vapour pressure of liquid decreases, and with a rising temperature vapour pressure of liquid increases. A mercury manometer may be used to determine the vapour pressure of a liquid.

Summary. An increase in the number of gas molecules, while container volume stays constant, increases pressure. A decrease in container volume increases gas pressure. An increase in temperature of a gas in a rigid container increases the pressure.

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.

Given that vapor depression is a colligative property, dependent on the number of moles of solute in solution, solutes with lower molecular mass should cause less vapor pressure depression.

The pressure exhibited by vapor present above a liquid surface is known as vapor pressure. As the temperature of a liquid increases, the attractive interactions between liquid molecules become less significant in comparison to the entropy of those molecules in the gas phase, increasing the vapor pressure.

The relation between relative lowering of vapour pressure and molar mass is. P01−PP01=W2M1W1M2. ∴ΔPP01=n2n1=W2M2W1M1=W2M1W1M2. Hence, by determining the vapour pressure of a pure solvent and a solution, the molar mass of a non-volatile solute can be measured.

So pressure is proportional to the number of moles of gas, not the mass of the gas. If you replace a given gas with one with double the molecular weight, for n to be the same, the mass of the replacement gas has to be double the mass. Yet the pressure is the same. Pressure is not dependent on mass.

The odor and color of the vapor do not affect the pressure of the vapor, so vapor pressure cannot be directly proportional to these two properties. There is a relationship between molar mass and vapor pressure but it is inversely proportional. The greater the molar mass of the substance, the lower its vapor pressure.