Increasing vapor pressure in water

[gsingh2011]

Why does adding salt to water increase the vapor pressure? Does increasing the volume of water increase the vapor pressure?

 

[Ygggdrasil]

Why does adding salt to water increase the vapor pressure?

Adding salt to water decreases the vapor pressure of the solution.

Does increasing the volume of water increase the vapor pressure?

No, vapor pressure is independent of volume. First, you need to consider the main thermodynamic driving force for the conversion of liquid water to gaseous water. Is this process driven by water seeking a lower potential energy (enthalpy)? Is it driven by the increase in entropy?

 

[quicknote]

I can explain the phenomenon of increasing vapor pressure in water and the effect of adding salt and increasing the volume of water.

First, let's define vapor pressure. Vapor pressure is the pressure exerted by the vapor of a liquid in a closed container at a given temperature. In other words, it is the pressure at which the liquid and its vapor are in equilibrium.

Now, when we add salt to water, it increases the vapor pressure of the solution. This is because salt molecules dissolve in water, breaking down into positively charged sodium ions and negatively charged chloride ions. These ions attract water molecules, pulling them away from each other and allowing them to escape into the gas phase more easily. This results in an increase in the number of water molecules in the vapor phase and therefore an increase in vapor pressure.

On the other hand, increasing the volume of water alone does not directly affect the vapor pressure. The vapor pressure of a liquid is primarily determined by its temperature and the strength of intermolecular forces between its molecules. Increasing the volume of water may affect the temperature and pressure of the system, but it does not directly impact the vapor pressure.

However, if we increase the volume of water while keeping the amount of salt constant, the vapor pressure may increase due to the increased surface area available for water molecules to escape into the gas phase. This is because more water molecules can break away from the surface and enter the vapor phase in a larger volume of water compared to a smaller volume.

In conclusion, adding salt to water increases the vapor pressure due to the presence of ions that attract water molecules and allow them to escape into the gas phase more easily. Increasing the volume of water may indirectly affect the vapor pressure by altering the temperature and pressure of the system, but the amount of salt present will also play a role.