Adding a solute to a solvent extends the temperature range over which the liquid exists in equilibrium. Therefore the melting point is lowered and the boiling point is raised.
If you want to understand the raising of the boiling point, note that some solute molecules or ions occupy spaces at the liquid-vapor interface, making it harder for the solvent molecules to escape into the vapor.
If you want to understand the lowering of melting point: the solute molecules or ions hinder the solvent molecules in arranging themselves in a crystal lattice, so you need a lower temperature to make that happen.
Since the boiling point of two chemicals is generally somewhere between the boiling point of each seperatly, and since salt boils at a very high temperature, I guess the combination would boil at a higher temperature than water alone.
Salt decreases the melting point of ice! Will salt decrease the boiling point of water ?
The melting point of a frozen, solid, solution is lower than the melting point of a pure substance.
The boiling point of a liquid solution is higher than the boiling point of the pure substance.
The freezing point of a liquid solution is lower than the freezing point of a pure substance.
The salt lowers the freezing point and raises the boiling point!
This means salt water can exist as a liquid from temperature below 0°C to above 100° C.
Question#2
How can salt water exist at a broader range of temperature than pure water??
What has changed when salt is dissolved in water??
Boiling occurs when the vapor pressure of a liquid equals the atmospheric pressure. Vapor pressure increases as temperature increases.
The salt must have lowered the vapor pressure. This means the vapor pressure of the salt water at 100°C was not equal to the atmospheric pressure. The salt water had to be heated to a temperature higher than 100°C to increase the vapor pressure.
The bonds between the Na+1 and Cl-1 ions and the polar H2O molecule are strong enough to decrease the number of H2O molecule escaping from the surface. Escaping from the surface, evaporation is the cause of vapor pressure!
The frozen solution is a mixture of separate NaCl•2H2O crystals and ice crystals , not a homogeneous mixture of salt and water.
During freezing, the water molecules must separate from the ions of salt and bond with other water molecules, to form pure ice crystals. The kinetic energy of the solution must decrease, so this breaking bonds and making bonds can occur. The temperature must be lower, so the KE is lower, so the H2O can find his buddies and become crystals of ICE, frozen H2O.
IF you freeze sugar water, you will notice that the “pop-cycle” is much easier to chew than an ice cube.
Pure ice is much harder than frozen salt water or sugar water. The bonds between solid ice and salt are much weaker than the bonds between water molecules in pure ice!
The energy required to melt and boil is proportional to the bonds between the molecules and ions of the solute and solvent.
No, it raises it. According to one comment in this discussion, it raises it by about half a degree C for each 5.8% (58 grams salt per 1000 grams of water).
Answers & Comments
Verified answer
Adding a solute to a solvent extends the temperature range over which the liquid exists in equilibrium. Therefore the melting point is lowered and the boiling point is raised.
If you want to understand the raising of the boiling point, note that some solute molecules or ions occupy spaces at the liquid-vapor interface, making it harder for the solvent molecules to escape into the vapor.
If you want to understand the lowering of melting point: the solute molecules or ions hinder the solvent molecules in arranging themselves in a crystal lattice, so you need a lower temperature to make that happen.
Since the boiling point of two chemicals is generally somewhere between the boiling point of each seperatly, and since salt boils at a very high temperature, I guess the combination would boil at a higher temperature than water alone.
Salt decreases the melting point of ice! Will salt decrease the boiling point of water ?
The melting point of a frozen, solid, solution is lower than the melting point of a pure substance.
The boiling point of a liquid solution is higher than the boiling point of the pure substance.
The freezing point of a liquid solution is lower than the freezing point of a pure substance.
The salt lowers the freezing point and raises the boiling point!
This means salt water can exist as a liquid from temperature below 0°C to above 100° C.
Question#2
How can salt water exist at a broader range of temperature than pure water??
What has changed when salt is dissolved in water??
Boiling occurs when the vapor pressure of a liquid equals the atmospheric pressure. Vapor pressure increases as temperature increases.
The salt must have lowered the vapor pressure. This means the vapor pressure of the salt water at 100°C was not equal to the atmospheric pressure. The salt water had to be heated to a temperature higher than 100°C to increase the vapor pressure.
The bonds between the Na+1 and Cl-1 ions and the polar H2O molecule are strong enough to decrease the number of H2O molecule escaping from the surface. Escaping from the surface, evaporation is the cause of vapor pressure!
http://antoine.frostburg.edu/chem/senese/101/solut...
The frozen solution is a mixture of separate NaCl•2H2O crystals and ice crystals , not a homogeneous mixture of salt and water.
During freezing, the water molecules must separate from the ions of salt and bond with other water molecules, to form pure ice crystals. The kinetic energy of the solution must decrease, so this breaking bonds and making bonds can occur. The temperature must be lower, so the KE is lower, so the H2O can find his buddies and become crystals of ICE, frozen H2O.
IF you freeze sugar water, you will notice that the “pop-cycle” is much easier to chew than an ice cube.
Pure ice is much harder than frozen salt water or sugar water. The bonds between solid ice and salt are much weaker than the bonds between water molecules in pure ice!
The energy required to melt and boil is proportional to the bonds between the molecules and ions of the solute and solvent.
I hope this helps you understand!
No, it raises it. According to one comment in this discussion, it raises it by about half a degree C for each 5.8% (58 grams salt per 1000 grams of water).
http://www.newton.dep.anl.gov/askasci/gen01/gen010...
No I mean.
Thought you said increase.
The more distilled the water, the less energy required to get it to latent heat of vaporization.