Water and Aqueous Systems Quick Review

Properties of Water Hydrogen bonding – Result in high surface tension and low vapor pressure – **What is a surfactant? – Extensive hydrogen bonding in ice holds the water molecules farther apart in a more ordered crystal structure arrangement (hexagonal symmetry) than in liquid water.

Solutions A solution is a HOMOGENEOUS MIXTURE. A solution has two parts: – Solvent- whatever is doing the dissolving – Solute-whatever is being dissolved Types of solutions: 1.Gases dissolved in liquids (carbonated beverages) 2.Liquids dissolved in liquids (alcohol) 3.Gases dissolved in other gases (air) 4.Gases dissolved in solids (air in ice) 5.Solids dissolved in solids (alloys…brass is zinc and copper) 6.Solids dissolved in liquids (saltwater)

The solution process Water molecules are polar, with + and – sides. If we dissolve an ionic substance, the polar solvent molecules attract the solute ions. As individual solute ions break away from the crystal, the negatively and positively charged ions become surrounded by solvent molecules and the ionic crystal dissolves. This is called SOLVATION.

Like Dissolves Like Means that a solvent will dissolve a solute that is similar. – A nonpolar solvent will dissolve a nonpolar solute. – A polar solvent will dissolve both polar and ionic solutes. – An ionic solid will only be dissolved by a polar solvent.

Electrolytes An electrolyte is a compound that conducts an electric current when it is in an aqueous solution or in the molten state. Conduction of electicity requires ions that are mobile and thus able to carry an electrical current. All ionic compounds are electrolytes because they dissociate into ions.

Strong vs. Weak Electrolytes Dissociation-the process of an ionic solid splitting into its’ ions. Strong electrolyte-a compound with a high dissociation rate (ex: Salt, strong acids & bases) Weak electrolyte-a compound or molecule with low dissociation rate (ex: ammonia, weak acids, sugar)

Hydrates A compound that contains water of hydration. FeSO 4 · 7H 2 O Barium Hydroxide Octahydrate Percent by Mass: – Calculate the percent of mass by water Sodium Carbonate Decahydrate

Suspensions and Colloids PropertySolutionColloidSuspension Particle type Ions, atoms, small moleculesLarge molecules or particlesLarge particles or aggregates Effect of Light No scatteringExhibits Tyndall Effect Filtration Particles not retained on filter Particles retained on filter Uniformity HomogeneousHeterogeneous Effect of gravity Stable, does not separate Unstable, sediment forms Examples SaltwaterWhipped Cream, mayonnaise*, Fog Gravy, Whole Milk