Colligative properties
Published on Mar 19, 2020
No Description
MORE DECKS TO EXPLORE
PRESENTATION OUTLINE
Colligative properties
Depend on the number of particles, not necessarily their identity
Photo by anuwish
Colligative properties are those properties of solutions that depend on the number of dissolved particles in solution, but not on the identities of the solutes. For example, the freezing point of salt water is lower than that of pure water, due to the presence of the salt dissolved in the water. To a good approximation, it does not matter whether the salt dissolved in water is sodium chloride or potassium nitrate; if the molar amounts of solute are the same and the number of ions are the same, the freezing points will be the same.
Read more: Modern Chemistry Chapter 14
The presence of a solute lowers the freezing point of a solution relative to that of the pure solvent. For example, pure water freezes at 0°C (32°F); if one dissolves 10 grams (0.35 ounces) of sodium chloride (table salt) in 100 grams (3.53 ounces) of water, the freezing point goes down to −5.9°C (21.4°F). If one uses sucrose (table sugar) instead of sodium chloride, 10 grams (0.35 ounces) in 100 grams (3.53 ounces) of water gives a solution with a freezing point of −0.56°C (31°F). The reason that the salt solution has a lower freezing point than the sugar solution is that there are more particles in 10 grams (0.35 ounces) of sodium chloride than in 10 grams (0.35 ounces) of sucrose. This is called freezing point depression.
This is called Freezing point depression
-Co/Colligative-Properties.html#ixzz6HBFJ3Gah
One can calculate the change in freezing point (Δ T f ) relative to the pure solvent using the equation:
Δ T f = i K f m
where K f is the freezing point depression constant for the solvent (1.86°C·kg/mol for water), m is the number of moles of solute in solution per kilogram of solvent, and i is the number of ions present per formula unit (e.g., i = 2 for NaCl)
Read more: http://www.chemistryexplained.com/Ce-Co/Colligative-Properties.html#ixzz6HB...
Boiling point elevation
Click The boiling point of a solution is higher than that of the pure solvent. Accordingly, the use of a solution, rather than a pure liquid, in antifreeze serves to keep the mixture from boiling in a hot automobile engine. As with freezing point depression, the effect depends on the number of solute particles present in a given amount of solvent, but not the identity of those particles.
Read more: http://www.chemistryexplained.com/Ce-Co/Colligative-Properties.html#ixzz6HB... boiling point of a solution is higher than that of the pure solvent. Accordingly, the use of a solution, rather than a pure liquid, in antifreeze serves to keep the mixture from boiling in a hot automobile engine. As with freezing point depression, the effect depends on the number of solute particles present in a given amount of solvent, but not the identity of those particles.
Read more: http://www.chemistryexplained.com/Ce-Co/Colligative-Properties.html#ixzz6HB... more text here
The boiling point of a solution is higher than that of the pure solvent. Accordingly, the use of a solution, rather than a pure liquid, in antifreeze serves to keep the mixture from boiling in a hot automobile engine. As with freezing point depression, the effect depends on the number of solute particles present in a given amount of solvent, but not the identity of those particles.
Two other colligative properties are
vapor pressure lowering and osmotic pressure
why do we add salt to roads before they freeze?
Photo by fatboyke (Luc)
