Chapter 12Chapter 12

SolutionsSolutions

12.1 Types of Mixtures

Classification of MatterClassification of MatterSolutions are

homogeneous

mixtures!

SoluteSoluteA solute is the dissolved substance in a solution.

A solvent is the dissolving medium in a solution.

SolventSolvent

Salt in salt water

Sugar in soda drinks

Carbon dioxide in soda drinks

Water in salt water

Water in soda

Types of Solutions Types of Solutions

• Gaseous mixturesGaseous mixtures

Air is a solution Air is a solution

• Solid solutionsSolid solutions

Metal alloys Metal alloys

• Liquid solutions Liquid solutions

Liquid dissolved in a liquid Liquid dissolved in a liquid

(alcohol in water) (alcohol in water)

Solid dissolved in a liquidSolid dissolved in a liquid

(salt water) (salt water)

Concentrated vs. DiluteConcentrated vs. Dilute

Suspensions and ColloidsSuspensions and Colloids

Suspensions and colloids are NOT solutions.

Suspensions: The particles are so large that they settle out of the solvent if not constantly stirred. Particles can be filtered out.Example: Oil & Water

Colloids: The particles intermediate in size between those of a suspension and those of a solution. Particles cannot be easily filtered out.Example: Milk

Smoke is a solid in a

gas. Fog is a

liquid in a gas.

Milk of Magnesia is a sol with solid magnesium hydroxide in

water

Mayonnaise is oil in water

Gelatin is protein in

water. Quicksand is sand in

water

The Tyndall EffectThe Tyndall Effect

Colloids scatter light, making a beam visible. Solutions do not scatter light.

Which glass contains a colloid? solutioncolloid

The ammeter measures the flow of electrons (current) through the circuit.

If the ammeter measures a current, and the bulb glows, then the solution conducts.

If the ammeter fails to measure a current, and the bulb does not glow, the solution is non-conducting.

Electrolytes vs. NonelectrolytesElectrolytes vs. Nonelectrolytes

An electrolyte is: A substance whose aqueous solution conducts

an electric current.

A nonelectrolyte is:

A substance whose aqueous solution does not conduct an electric current.

Try to classify the following substances as electrolytes or nonelectrolytes…

Definition of Electrolytes and Definition of Electrolytes and NonelectrolytesNonelectrolytes

1. Pure water2. Tap water3. Sugar solution4. Sodium chloride solution5. Hydrochloric acid solution6. Lactic acid solution7. Ethyl alcohol solution8. Pure sodium chloride

Electrolytes?Electrolytes?

Electrolytes: Nonelectrolytes:

Tap water (weak)

NaCl solution

HCl solution

Lactate solution (weak)

Pure water

Sugar solution

Ethanol solution

Pure NaCl

But why do some compounds conduct electricity insolution while others do not…?

Chapter 12Chapter 12

SolutionsSolutions

12.2 The Solution Process

Dissolution of sodium ChlorideDissolution of sodium Chloride

The Hydration Process

Saturation of SolutionsSaturation of Solutions A solution that contains the maximum A solution that contains the maximum

amount of solute that may be dissolved amount of solute that may be dissolved under existing conditions is under existing conditions is saturatedsaturated..

A solution that contains less solute than a A solution that contains less solute than a saturated solution under existing saturated solution under existing conditions is conditions is unsaturatedunsaturated..

A solution that contains more dissolved A solution that contains more dissolved solute than a saturated solution under the solute than a saturated solution under the same conditions is same conditions is supersaturatedsupersaturated..

Factors Affecting the Rate of Factors Affecting the Rate of Dissolution Dissolution

• Increasing the Surface Area of the SoluteIncreasing the Surface Area of the Solute

Finely divided substances dissolve more rapidly Finely divided substances dissolve more rapidly

• Agitating a SolutionAgitating a Solution

Stirring or shaking brings solvent into contact with Stirring or shaking brings solvent into contact with more solute particles more solute particles

Added energy temporarily increases solubility Added energy temporarily increases solubility

• Heating Heating

Heating almost always increasing the rate of Heating almost always increasing the rate of dissolution of solids in liquids dissolution of solids in liquids

““Like dissolves like”Like dissolves like”

• Polar substances dissolve in polar solvents Polar substances dissolve in polar solvents • Nonpolar substances dissolve in nonpolar solvents Nonpolar substances dissolve in nonpolar solvents

• Examples:Examples:• Polar and ionic compounds are not soluble in Polar and ionic compounds are not soluble in

nonpolar solvents nonpolar solvents • Fats, oils and many petroleum products are soluble in Fats, oils and many petroleum products are soluble in

nonpolar solvents nonpolar solvents

• Nonpolar solvents include CClNonpolar solvents include CCl44 and toluene (methyl and toluene (methyl

benzene), Cbenzene), C66HH55CHCH33

• Liquid Solutes and SolventsLiquid Solutes and Solvents Immiscible - Liquid solutes and solvents that are Immiscible - Liquid solutes and solvents that are not soluble in each other not soluble in each other

Ex: Oil and waterEx: Oil and water Miscible - Liquids that dissolve freely in one Miscible - Liquids that dissolve freely in one another in any proportion another in any proportion

Ex: Benzene and carbon tetrachloride (both nonpolar) Ex: Benzene and carbon tetrachloride (both nonpolar) Ex: Water and ethanol (both polar) Ex: Water and ethanol (both polar)

• HydratesHydrates Ionic substances that incorporate water molecules Ionic substances that incorporate water molecules into their structure during the recrystallization into their structure during the recrystallization process process

Ex: CuSOEx: CuSO44•5H•5H22O O

Saturation and EquilibriumSaturation and Equilibrium

The physical state in which the opposing processes of dissolution and crystallization of a solute occur at equal rates

Effects of Pressure on SolubilityEffects of Pressure on Solubility • Pressure has no real effect on the solubilities of liquids Pressure has no real effect on the solubilities of liquids

and solids in liquid solvents and solids in liquid solvents • Increasing pressure increases the solubility of gases in Increasing pressure increases the solubility of gases in

liquids liquids

• Henry's Law Henry's Law • The solubility of a gas in a liquid The solubility of a gas in a liquid

is directly proportional to the is directly proportional to the partial pressure of that gas on the partial pressure of that gas on the surface of the liquid surface of the liquid

• Effervescence Effervescence • The rapid escape of a gas from a liquid in which it is The rapid escape of a gas from a liquid in which it is

dissolved dissolved

Effects of Temperature on SolubilityEffects of Temperature on Solubility

• Solubility of solids increases with temperature Solubility of solids increases with temperature • Solubility of gases decreases with temperature Solubility of gases decreases with temperature

Solubility TrendsSolubility Trends The solubility of MOST solids increases The solubility of MOST solids increases

with temperature.with temperature. The rate at which solids dissolve The rate at which solids dissolve

increases with increasing surface area of increases with increasing surface area of the solid.the solid.

The solubility of gases decreases with The solubility of gases decreases with increases in temperature.increases in temperature.

The solubility of gases increases with the The solubility of gases increases with the pressure above the solution.pressure above the solution.

Therefore…Therefore…Solids tend to dissolve best when:

o Heatedo Stirredo Ground into small particles

Liquids & Gases tend to dissolve best when:

o The solution is coldo Pressure is high

Heat of SolutionHeat of SolutionThe Heat of Solution is the amount of heat energy absorbed (endothermic, positive) or released (exothermic, negative) when a specific amount of solute dissolves in a solvent.

SubstanceSubstance Heat of Solution Heat of Solution

(kJ/mol)(kJ/mol)NaOHNaOH -44.51-44.51

NHNH44NONO33 +25.69+25.69

KNOKNO33 +34.89+34.89

HClHCl -74.84-74.84

Chapter 12Chapter 12

SolutionsSolutions

12.3 Concentration of Solution

Molarity (M)Molarity (M)The concentration of a solution measured in moles of solute per liter of solution.

mol = M L

Pronounced “molar”

Molality (m)Molality (m)

The concentration of a solution in moles of solute per kilogram of solvent.

Since the most common solvent, water, has a density of 1 kg/L, one kilogram of water is the same as one liter of water!

mol = mmkg

DilutionsDilutions• If a solution of known concentration and volume has If a solution of known concentration and volume has

been diluted, we can calculate the new concentration:been diluted, we can calculate the new concentration:

MM11VV11 = M = M22VV22

Example:Example:

20.00 mL of a 0.500 M KBr solution is diluted to 100.00 mL. 20.00 mL of a 0.500 M KBr solution is diluted to 100.00 mL. What is the new molarity?What is the new molarity?

(20.00mL)(0.500M) = (100.00mL)(M(20.00mL)(0.500M) = (100.00mL)(M22))

MM22 =0.100 M =0.100 M

Additional practice problems located in Appendix D p. 902Additional practice problems located in Appendix D p. 902