solutions

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Solutions

Solutions are homogeneous (single-phase) mixtures of two or more components. They are extremely important in Chemistry because they allow intimate and varied encounters between molecules of di?erent kinds, a condition that is essential for rapid chemical reactions to occur.

Molarity: Molarity is defined as the number of moles of solute dissolved per litre of solution and is usually denoted by M. It is expressed as : M= n/V

Normality : Normality is the number of gram equivalent weights of solute dissolved per litre of the solution.

Types of solutions :-

 Gaseous solutions like air

 Solutions of gases in liquids like soda water

 Solutions of liquids in liquids like alchol

 Solutions of molecular solids in liquids

 Solutions of ionic solids in water

Colligative Properties are those properties of a liquid that may be altered by the presence of a solute. Colligative means “depending on the collection” because the magnitude of the change is due to the number of particles in the solution and not their chemical identity. Examples of properties that fall under this category are the vapor pressure, melting and boiling points, and osmotic pressure.

The vapour pressure of a solution of a non-volatile solute is equal to the vapour pressure of the pure solvent at that temperature multiplied by its mole fraction.

Psolution = XsolventPosolvent

The freezing point is the temperature at which solid and liquid can simultaneously coexist, meaning that the escaping tendencies of molecules from the two phases is the same. Suppose now that we dilute the solvent by adding some solute. The escaping tendency of solvent molecules from the liquid phase is now reduced owing to their increased disorder in the solution, but in the solid nothing has changed and the escaping tendency of solvent molecules from this phase remains the same. This means that there will be a net movement of solvent molecules from the solid phase to the liquid; the solid melts. In order to keep the solid from melting, the escapingtendency of molecules from the solid must be reduced. This can be accomplished by reducing the temperature; this lowers the escaping tendency of molecules from both phases, but it a?ects those in the solid more than those in the liquid, so we eventually reach the new, lower freezing point where the two quantities are again in exact balance and both phases can coexist.

Osmosis is the process in which a liquid passes through a membrane whose pores permit the passage of solvent molecules but are too small for the larger solute molecules to pass through.

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