Unit 10 – Solutions!

Chapter 14

What is a solution?• Solutions are mixtures

• Solutions are homogenous

• Solutions are stable

• In a Solution, particles are evenly dispersed throughout the liquid, but aren’t really bonded to the liquid (just hangin’ out in there)

Definitions

• Suspension: looks uniform when stirred, but separates on standing

• Solvent: The “stuff” that does the dissolving (remember the “v” that is in “solvent” and “dissolve”

• Solute: The “stuff” that gets dissolved by the solvent

Types of Solutions:• Alloy: a solid or liquid mix of two metals• Unsaturated: you can put more solute in• Saturated: things are dissolving at the same

rate that they are precipitating (falling out of solution)

• Supersaturated: has more solute than it can normally hold (think of growing sugar crystals).

Iced Tea….

• Why do people who like sweet ice tea make hot tea first, add sugar, and then pour it over ice?

• Soluble: the solute can be dissolved by a particular solvent

• Insoluble: the solute can not be dissolved by a particular solvent!

• Solubility: the maximum solute that a particular solvent can dissolve (g solute per g solvent)

Gases in Solution

• The solubility of liquids and solids does not change appreciably with pressure.

• The solubility of a gas in a liquid is directly proportional to its pressure.

Why Things Dissolve

• Polarity: an imbalance of the partial positive and partial negative charges in a compound

• “Like Dissolves Like” – Polar solvents will dissolve polar solutes– Non polar solvents will dissolve nonpolar

solutes.

• Miscible: two liquids or gases that will dissolve in each other.

• Immiscible: two liquids or gases that will not dissolve in each other!!

Solutions

The intermolecular forces between solute and solvent particles must be strong enough to compete with those between solute particles and those between solvent particles.

How Does a Solution Form?

As a solution forms, the solvent pulls solute particles apart and surrounds, or solvates, them.

Solubility Rules

• Rules that are a guide to whether or not a particular substance is soluble in water.

Precipitation Reactions

• A Precipitate is an insoluble product that is formed from two soluble reactants.– A precipitate can no longer be shown as ions in

solution

• When ionic compounds are in solution and they are soluble, we can show them as ions:– Na+ + Cl- is really NaCl dissolved in a solvent.

Net Ionic Equations

• Net ionic equations are equations where:– All soluble ionic compounds are shown as their

respective ions.– All insoluble compounds are no longer shown

as ions– All ions that are unchanged are crossed out.

• Use solubility tables to find out what is soluble and what is not.

Example:

• Write the net ionic eqn. For the rxn. Of solutions of silver nitrate and potassium chloride:

Solvents:

• What kind of solvents do you have in your house? What kinds of dangers do they pose?

• Why is the volume of water and ethanol when mixed not equal to the volume of water + ethanol when separate?