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