The Formations of Solutions

Objectives:

1. Explain the process by which solutions form.

2. Give the definition of solubility and explain how it is affected by various factors.

Key Terms:

solvation hydration solubility

Notes: (15-3)

At some point you may have heard the phrase "like dissolves like" (polar dissolves polar and non-polar dissolves non-polar). To understand this phenomena you must consider the intermolecular forces at work in a solution. If the intermolecular forces present in the solution are compatible with the solvent, the solvent is considered soluble.

	Solvation is the term given to the interaction between solvent and solute.
	If the solvent is water the reaction is called hydration - water is the most common polar solvent

(w3.rz-berlin.mpg.de/~mwolf/newfemtos/ eldyn/solvation.gif)

(omega.dawsoncollege.qc.ca/ ray/chemistry/nacl3.gif)

The solubility is the amount of solute that can dissolve in a solution at given conditions. It depends on several conditions and is expressed in grams of solute per 100grams of solvent.

Temperature

Solubility of a gas is decreased with an increase in temperature

due to an increase in the kinetic energy of the molecules

Solubility of a solid is usually increased with an increase in temperature (endothermic reactions)

	exception:
	Exothermic - increasing temperature decreases solubility
	an increase temperature has no effect on solubility when there is no temperature change for the solution

Pressure

	Solubility of a gas is increased with and increase in pressure
	Solubility of of a solid is usually unaffected by pressure

Factors affecting the rate of dissolving

Surface area

	The greater the surface area the greater the rate of dissolving
	Breaking the solute into smaller pieces increases the surface area

Stirring - increases the rate of dissolving by bringing solvent in contact with solute

Temperature - increases rate by increasing the kinetic energy of the solvent

Last modified: March 31, 2003