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Modern Chemistry Chapter 12-Solutions
Section 1- Types of Mixtures
• Solutions are homogeneous mixtures of two or more substances in a single phase.
– Soluble describes a substance as capable of being dissolved.
– Solvent is the dissolving medium in a solution.
– Solute is the substance that is dissolved in a solution.
Types of Solutions
• Solutions can be in any of the three common physical states.
solid- a mixture of metals called an alloy
liquid- salt water, sugar water, Kool-Aid…
gas- the atmosphere
Suspensions & Colloids
• A suspension has large particles that settle out of a solvent. eg. muddy water
• A colloid has intermediate size particles. Also called an emulsion or a foam.
Solutes: electrolytes vs. nonelectrolytes
• An electrolyte is a substance that dissolves in water to give a solution that conducts electricity.
• A nonelectrolyte is a substance that dissolves in water to give a solution that does NOT conduct electricity.
• Do section review questions #1, #2, & #6 on page 406.
Section 2- The Solution Process
• Factors that affect the rate of solution (how quickly a substance dissolves):– Any process that increases the number of
contacts between the solvent and the solute will increase the solution rate.
• increasing the surface area of the solute• agitating (shaking or stirring) the solution• heating the solvent
Solutions
• Solution equilibrium is the physical state in which the opposing processes of dissolution and crystallization occur at equal rates.
• A saturated solution contains the maximum amount of dissolved solute.
• An unsaturated solution contains less than the maximum amount of dissolved solute.
• A supersaturated solution contains more dissolved solute than a saturated solution.
Solubility• Solubility is a measurement of how much solute will dissolve in a specific
amount of solvent at a specific temperature to make a saturated solution.
• “Likes dissolve likes”- polar solvents dissolve polar solutes & nonpolar solvents dissolve nonpolar solutes.
• Hydrationis the solution process with water as the solvent.
• Hydrates are ionic compounds that have formed crystals that have incorporated water molecules in their structure.
• Immiscible liquids are not soluble in one another. eg. oil & water
• Miscible liquids dissolve freely in one another in any proportion. eg. water & alcohol
Solubility• Increasing the pressure has no effect on the solubility of a solid in a liquid
but does increase the solubility of gases in a liquid.
• Increasing temperature often increases the solubility of a solid in a liquid but decreases the solubility of a gas in a liquid.
• Henry’s Law states that the solubility of a gas in a liquid is directly proportional to the partial pressure of the gas on the surface of the liquid.
• Effervescence is the rapid escape of a gas from a liquid in which the gas is dissolved.
• A solvated solute particle is surrounded by solvent molecules.
• Enthalpy of solution is the amount of heat absorbed by a solution when a specific amount of solute dissolves in a solvent.
Problems
• Do section review questions #1, #2, #3, #5, & #6 on page 416.
• Read the Cross-Disciplinary Connection on page 417 and answer the questions at the end of the reading.
Section 3Concentrations of Solutions
• The concentration of a solution is a measure of the amount of solute dissolved in a given amount of solvent or solution.
• Molarity (M) is the number of moles of solute in one liter of solution.
M = #mol L
• Do practice problems #1, #2, & #3 on page 421.
Solution Concentrations
• Molality (m) is the concentration of a solution expressed in moles of solute per kilogram of solvent.
m = #mol
kg
Do practice problems #1 & #2 on page 424.
Solution Concentrations
• Percent composition by mass (%) is a concentration that expresses the percent of solute in a solution.
% = #g solute x 100
# g solution
Do section review problems #1, #2, & #3 on page 424.
Chapter 12 Test Review
• multiple choice (30)– define & identify suspensions & solutions– define an alloy– define & identify electrolytes & nonelectrolytes– factors that affect the rate of dissolution– definitions of unsaturated, saturated & supersaturated solutions– general rules for predicting whether a solute is soluble in a
solvent– definition of solubility– effects of temperature & pressure on the solubility of gases and
solids in liquids– definitions of molarity (M) and molality (m)– solving molarity & molality problems– FORMULAS: M = #mol/L m = #mol/kg