CHEMISTRY | Sec.1 | Collective Properties of Solutions #1 | Unit 3 - Chapter 1 - Lesson 3

Описание: شرح درس
Collective Properties of Solutions
CHEMISTRY - Secondary 1
In This part we will study
The properties of solutions differ from the properties of the pure solvents forming them after dissolving nonvolatile substances in them at the same conditions, these new properties are called
Colligative (Collective) properties of solutions: They are properties whose values depend only on the number of solute particles per unit volume of solution and not on the type of solute.
 Vapor pressure depression:
When a pure liquid is left in an open beaker, it evaporates completely.
But, when it is left in a closed container, both liquid and vapor are present.
(i.e.) Vaporization and condensation occur.
At equilibrium, the rate of condensation is equal to the rate of vaporization and the pressure exerted by this vapor is called Vapor pressure.

Vapor pressure: They are properties whose values depend only on the number of solute particles per unit volume of solution and not on the type of solute.
Vapor pressure of the pure liquids or solutions is not affected by :
• Change in the external pressure.
• Increasing or decreasing the amount of the liquid.
The vapor pressure of a pure solvent is affected by dissolving a non-volatile solute in it to form a solution as follows :

The vapor pressure of the solution is always lower than the vapor pressure of the pure solvent, because the number of solvent surface molecules in solution is less than that in the pure solvent, as the attraction forces between solvent and solute molecules in the solution is stronger than the attraction forces between the solvent molecules with each other.
So, the number of solvent molecules which exposed to vaporization process decreases in the solution.

The decrease in vapour pressure of the solution depends on the number of moles (of ions or molecules) of the solute not the type of solution, where the vapor pressure decreases by increasing the number of moles of the solute.


Best wishes to you
Mr.Ahmed Elbasha

كيمياء الصف الاول الثانوي لغات - الفصل الدراسي الاول
شرح كيمياء لغات اولي ثانوي - مستر احمد الباشا
كيمياء لغات - الصف الاول الثانوي - كيمياء اولي ثانوي الترم الاول - كيمستري اولي ثانوي الترم الاول