c hapter 16 solutions. s olution f ormation compositions of the solutes and solvents determine if...

CHAPTER CHAPTER 1616SolutionsSolutions

SOLUTION

SOLUTION

FORMATION

FORMATION

Compositions of the solutes and solvents determine if the substance will dissolve.

Stirring, temperature, and surface area determines how fast the substance dissolves.

Stirring and heating increase the rate at which a solute dissolves. (a)

A cube of sugar in cold tea dissolves slowly. (b) Granulated sugar

dissolves in cold water more quickly than a sugar cube, especially

with stirring. (c) Granulated sugar dissolves very quickly in hot tea.

HENRY’S LAW

HENRY’S LAW

At a given temperature the solubility of a gas in a liquid is directly proportional to the pressure of the gas above the liquid

S1 is the solubility

of a gas at one pressure,

P1;S2

is the solubility at another pressure, P2

.

SolubilitySolubility:: amount of substance that dissolves in a given amount of solvent at specific conditions of temp. and pressure to produce a saturated solution

Unsaturated solutionUnsaturated solution: : contains less solute than a saturated solution at a given temperature and pressure

Saturated solutionSaturated solution: : contains the max amount of solute for a given amount of solvent at a constant temp. and pressure

Supersaturated solutionSupersaturated solution: : contains more solute than it can theoretically hold at a given temp.

MiscibleMiscible:: liquids that dissolve completely in one another

ImmiscibleImmiscible: : liquids that are insoluble in one another

16.1 VOCABULARY16.1 VOCABULARY

MOLARITMOLARIT

YY Divide the moles

of solute by the volume of solution.

Molarity(M)Molarity(M):: the concentration of solute in a solution expressed as the number of moles of solute dissolved in 1 liter of solution

DILUTIODILUTIONN

Diluting a solution reduces the number of moles of solute per unit volume, but the total number of moles of solute in solution does not change.

Moles of solute = molarity (M) × liters of solution (V)

Moles of solute before dilution = moles of solute after dilution

Moles of solute M1 x V1= M2 x V2

M1 and V1 are the molarity and volume of the initial solution, and

M2 and V2 are the molarity and volume of

the diluted solution.

Volumes can be liters or milliliters both V1 and V2 have to have the same units.

Adding solventto a concentrated

solutionlowers the

concentration,but the total number

ofmoles of solute

presentremains the same.

PERCENT PERCENT CONCENTRATIOCONCENTRATIO

NNExpress as a ratio

volume of solute to volume of solution

mass of solute to mass of solution

OR

The label clearly shows this solution of isopropyl alcohol from rubbing alcohol which is a 70% solution of isopropyl alcohol.

16.2 VOCABULARY 16.2 VOCABULARY ConcentrationConcentration:: measurement of amount of solute that is

dissolved in a given quantity of solvent (mol/L)

Dilute solutionDilute solution: : solution contains a small amount of solute

Concentrated solutionConcentrated solution: : solution contains a large amount of solute

COLLIGATIVE

COLLIGATIVE

PROPERTY

PROPERTY Three important colligative properties of solutions: vapor-pressure loweringboiling-point elevationfreezing-point depression.

a property of a solution that depends only upon the number of solute particles, and not upon their identities; boiling-point elevation, freezing-point depression, and vapor-pressure lowering are colligative properties

FACTORS DETERMINING HOW MUCH FACTORS DETERMINING HOW MUCH PROPERTIES OF THE SOLUTION DIFFER PROPERTIES OF THE SOLUTION DIFFER

FROM PROPERTIES OF THE PURE FROM PROPERTIES OF THE PURE SOLVENTSOLVENT

The decrease in a solution’s vapor pressure is proportional to the number of particles the solute makes in solution.

The magnitude of the freezing-point depression is proportional to the number of solute particles dissolved in the solvent and does not depend upon their identity.

The magnitude of the boiling-point elevation is proportional to the number of solute particles dissolved in the solvent.

Vapor PressureVapor Pressure Freezing Freezing PointPoint

Boiling PointBoiling Point

16.3 VOCABULARY16.3 VOCABULARY

Freezing point depressionFreezing point depression: the difference in temperature between the freezing point of the solution and the freezing point of the pure solvent

Boiling point elevationBoiling point elevation: the difference in temperature between the boiling point of a solution and the boiling point of the pure solvent

CONCENTRATION OF

CONCENTRATION OF

SOLUTION

SOLUTIONYou can express the concentration of solutions in two ways:

Unit molality Mole fractions

Molality is also known as molal concentration.

Unit molality (m)

Unit molality (m): the number of

moles of solute dissolved in 1

kilogram (1000 g) of solvent

The magnitudes of the freezing-point depression (ΔTf) and the boiling-point elevation (ΔTb) of a solution are directly proportional to the molal concentration (m), when the solute is molecular, not ionic.

(ΔTf) is the difference between the freezing

point of the solution and the freezing point of the

pure solvent

m is the molal concentration of the

solution

ΔTf = Kf × m

Kf is the molal freezing-point

depression constant

ΔTb = Kb × m

FREEZING POINT DEPRESSION FREEZING POINT DEPRESSION AND AND

BOILING POINT ELEVATIONBOILING POINT ELEVATION

Freezing Point Depression Boiling Point Elevation

(ΔTb) is the difference between the boiling point of the solution and the boiling point of the pure solvent

Kb, is the molal boiling-point

elevation constant

m is the molal concentration of the

solution

16.4 VOCABULARY

16.4 VOCABULARYMole fractionMole fraction:: the ratio of the moles of solute in solution to the total number of moles of both solvent and solute

Molal freezing-point depression constant KMolal freezing-point depression constant Kff: : the change in freezing point for a 1-molal solution of a nonvolatile molecular solute

Molal boiling-point elevation constant KMolal boiling-point elevation constant Kbb: : the change in boiling point for a 1-molal solution of a nonvolatile molecular solute