modern chemistry chapter 12- solutions

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