Presentation on theme: "Section 17.3 Homogeneous Aqueous Solutions. Solvents and Solutes l Solution - a homogenous mixture, that is mixed molecule by molecule. l Solvent - the."— Presentation transcript:
Section 17.3 Homogeneous Aqueous Solutions
Solvents and Solutes l Solution - a homogenous mixture, that is mixed molecule by molecule. l Solvent - the dissolving medium l Solute -the dissolved particles
Solvents and Solutes l Aqueous solution- a solution with water as the solvent. l Particle size less than 1 nm; cannot be separated by filtration
Aqueous Solutions l Water dissolves ionic compounds and polar covalent molecules best. l The rule is: “like dissolves like” l Polar dissolves polar. l Nonpolar dissolves nonpolar.
The Solution Process l Called “solvation” l Water breaks the + and - charged pieces apart and surrounds them. l In some ionic compounds, the attraction between ions is greater than the attraction exerted by water (don’t dissolve)
How Ionic solids dissolve in water H H O H H O H H O H H O H H O H H O H H O H H O H H O These ions have been surrounded by water, and are now dissolved! These ions have been pulled away from the main crystal structure by water’s polarity.
Electrolytes and Nonelectrolytes l Electrolytes- compounds that conduct an electric current in aqueous solution, or in the molten state l All ionic compounds are electrolytes; dissociate into ions (they are also called “salts”)
Electrolytes and Nonelectrolytes l Do not conduct? = Nonelectrolytes. l Most are molecular materials, because they do not have ions
Electrolytes and Nonelectrolytes l There are strong electrolytes (100% ions), and weak electrolytes (small fraction become ions) l Depends on: degree of ionization
Water of Hydration (or Water of Crystallization) l Water molecules are chemically bonded to solid salt molecules (not in solution) l These compounds have fixed amounts of water.
Water of Hydration (or Water of Crystallization) l The water can be driven off by heating: CuSO 4 5H 2 O CuSO 4 + 5H 2 O l Called copper(II)sulfate pentahydrate. - heat + heat
Hydrates l Since heat can drive off water, the forces holding it are weak l Some hydrates remove water from the air to form hydrates- these are called hygroscopic