chapter 14: solutions and their properties solution homogeneous mixture of two or more substances...

CHAPTER 14: SOLUTIONS AND THEIR CHAPTER 14: SOLUTIONS AND THEIR PROPERTIESPROPERTIES

SOLUTION homogeneous mixture of two SOLUTION homogeneous mixture of two or more substances in a single phase.or more substances in a single phase.

Solvent component present in the largest Solvent component present in the largest amount, substance doing the dissolvingamount, substance doing the dissolving

Solute component present in the smallest Solute component present in the smallest amount, the substance dissolved.amount, the substance dissolved.

Quantitative ways to describe a solution, Quantitative ways to describe a solution, solute, solvent (moles, mass, or volume) solute, solvent (moles, mass, or volume)

Molarity (M) = mole of solute/liter solutionMolarity (M) = mole of solute/liter solution Molality (m) = moles of solute/kg of solventMolality (m) = moles of solute/kg of solvent Mole fraction (X) = nA / (nA + nB …) Mole fraction (X) = nA / (nA + nB …)

moles of a given component divided by the moles of a given component divided by the total # of moles of all components. total # of moles of all components.

Quantitative ways to describe a solution, Quantitative ways to describe a solution, solute, solvent (moles, mass, or volume) solute, solvent (moles, mass, or volume)

Weight % = Weight % =

mass of solute/mass of solution * 100mass of solute/mass of solution * 100 ppm = mg solute/l L solvent ppm = mg solute/l L solvent

Normality (N) = # Equivalents / L Normality (N) = # Equivalents / L

PracticePractice

A solution is prepared by mixing 1.00 g A solution is prepared by mixing 1.00 g ethanol (Cethanol (C22HH55OH) with 100.0 g water to OH) with 100.0 g water to

give a final volume of 101 mL. give a final volume of 101 mL. Calculate the molarity, molality, Calculate the molarity, molality,

mole fraction, weight %, mole fraction, weight %, and ppm of ethanol in this solution. and ppm of ethanol in this solution.

Solution Process Solution Process

Intermolecular forces (likes dissolve likes)Intermolecular forces (likes dissolve likes) When liquids mix and form a solution they When liquids mix and form a solution they

are miscible are miscible Immiscible liquids do not mix. Immiscible liquids do not mix.

Terms with solutionsTerms with solutions

Solution TermsSolution Terms

SATURATED - A stable solution in which the SATURATED - A stable solution in which the maximum amount of solute has been dissolved maximum amount of solute has been dissolved

UNSATURATED -The concentration of solute is UNSATURATED -The concentration of solute is less than the saturated amount. less than the saturated amount.

SUPERSATURATED- A solution that contains SUPERSATURATED- A solution that contains more than the saturated amount of solute more than the saturated amount of solute

Solution DiagramsSolution Diagrams

How Solutions FormHow Solutions FormThermodynamicsThermodynamics

The formation of solutions is favored because The formation of solutions is favored because it creates a more disordered system. it creates a more disordered system.

If the process requires too much energy, the If the process requires too much energy, the process will not occur. The energy can be process will not occur. The energy can be calculated.calculated.

ThermodynamicsThermodynamicsof Solutionsof Solutions

For an ionic crystal, first the crystal must For an ionic crystal, first the crystal must break apart, negative the (negative) lattice break apart, negative the (negative) lattice energy, therefore a positive enthalpy. energy, therefore a positive enthalpy.

Then the ions must hydrate (be Then the ions must hydrate (be surrounded by water molecules) which has surrounded by water molecules) which has a negative enthalpy.a negative enthalpy.


Dissolve CaClDissolve CaCl2 2 in water and describe the in water and describe the

relationship between lattice energy and the relationship between lattice energy and the energy of hydrationenergy of hydration

Dissolve NHDissolve NH44Cl in water and describe the Cl in water and describe the

relationship between lattice energy and the relationship between lattice energy and the energy of hydrationenergy of hydration

Factors Affecting Solubility Factors Affecting Solubility Pressure and Temperature: Pressure and Temperature:

Gases dissolved in water demonstrationGases dissolved in water demonstration

Bromothymol Blue solution and Bromothymol Blue solution and Alka-Seltzer in 200 mL DI water Alka-Seltzer in 200 mL DI water


Pressure: Solubility of Gases in Liquids: Pressure: Solubility of Gases in Liquids:

Henry's Law: SHenry's Law: Sgg = k = k HH P Pgg


Solubility DiagramsSolubility Diagrams

Colligative Properties Colligative Properties

Changes in Vapor Pressure: Raoult’s LawChanges in Vapor Pressure: Raoult’s Law The vapor pressure over the solution is lower than the The vapor pressure over the solution is lower than the

vapor pressure of pure solvent.vapor pressure of pure solvent.

The vaopr pressure of the solvent PThe vaopr pressure of the solvent Psolvsolv is propotional to is propotional to

the relative number of solvent molecules in the solution, the relative number of solvent molecules in the solution, the solvent vapor pressure is proportional to the the solvent vapor pressure is proportional to the solventsolvent mole fraction. mole fraction.

ColligativeColligative Properties Properties Definitions Definitions

Raoult’s LawRaoult’s Law

PPsolvsolv = X = Xsolvsolv P Poosolvsolv

Raoult’s Law applies to ideal solutionsRaoult’s Law applies to ideal solutions

Roult’s Law Diagram


Raoult’s Law Adding a non volatile solute Raoult’s Law Adding a non volatile solute to a solvent lowers the vapor pressure of to a solvent lowers the vapor pressure of the solvent so the change in vapor the solvent so the change in vapor pressure of the solvent can be calculated pressure of the solvent can be calculated as a function of the mole fraction.as a function of the mole fraction.


The boiling point of a solution is related The boiling point of a solution is related to the solute concentration. to the solute concentration.

The boiling point elevation The boiling point elevation T Tbpbp is is directly proportional to the molality of directly proportional to the molality of the solute:the solute:

bp bp = K= Kbpbp m msolutesolute

molal boiling point elevation constant molal boiling point elevation constant has the units of degrees/molal (has the units of degrees/molal (ooC / C / mm).).


What quantity of elthylene glycol, What quantity of elthylene glycol, HOCHHOCH22CHCH22OH must be added to 125 g OH must be added to 125 g

of water to raise the boiling point of of water to raise the boiling point of 1.01.0ooC?C?

KKbpbp of water is + 0.5121 of water is + 0.5121ooC/mC/m


The freezing point of a solution is related to The freezing point of a solution is related to the solute concentration. the solute concentration.

The freezing point depression The freezing point depression T Tfpfp is directly is directly

proportional to the molality of the solute:proportional to the molality of the solute:

TTfp fp = K= Kfpfp m msolutesolute

molal freezing point depression constant has molal freezing point depression constant has

the units of degrees/molal (the units of degrees/molal (ooC / C / mm).).


In the northern United States, summer In the northern United States, summer cottages are usually closed up for the winter. cottages are usually closed up for the winter. When doing so the owners “winterize” the When doing so the owners “winterize” the plumbing by putting antifreeze, plumbing by putting antifreeze, HOCHHOCH22CHCH22OH, in the toilet tanks. Will adding OH, in the toilet tanks. Will adding

525 g of anitfreeze to 3 kg of water ensure 525 g of anitfreeze to 3 kg of water ensure that the water will not freeze at -25that the water will not freeze at -25ooC. C.

KKfpfp of water is -1.86 of water is -1.86 ooC/mC/m


Colligative Properties and Molar Mass Colligative Properties and Molar Mass DeterminationDetermination


Van’t Hoff Factor Van’t Hoff Factor ii

When an ionic compound dissolves in a When an ionic compound dissolves in a solvent, the number of ions determines the solvent, the number of ions determines the behavior of the solvent. behavior of the solvent.

For example, 1 m NaCl will lower the f.p. of For example, 1 m NaCl will lower the f.p. of water twice as much as 1 m sugar because water twice as much as 1 m sugar because NaCl breaks into 2 ions NaCl breaks into 2 ions


Van’t Hoff Factor Van’t Hoff Factor I I Diagrams & PhotoDiagrams & Photo Actually only dilute solutions behave in this Actually only dilute solutions behave in this

manner.manner.

Officially, Officially, i i = = T Tfp measuredfp measured

TTfp calculatedfp calculated

So often the value of So often the value of i i approaches a whole approaches a whole number.number.


Osmosis is the movement of Osmosis is the movement of solvent solvent molecules molecules through a semipermeable membrane from a region of through a semipermeable membrane from a region of lower to a region of higher lower to a region of higher solute solute concentration.concentration.


Osmotic Pressure the pressure created by the column Osmotic Pressure the pressure created by the column above the solution measured by the difference in above the solution measured by the difference in height between the solution in the tube and the level height between the solution in the tube and the level of water in the beaker.of water in the beaker.

Osmotic Terms


Osmotic Pressure is related to concentration.Osmotic Pressure is related to concentration.

Recall the Ideal Gas Law PV = nRTRecall the Ideal Gas Law PV = nRT

Rearrange the equation so the concentration is (n/V)Rearrange the equation so the concentration is (n/V)

P = (n/V) R TP = (n/V) R T

Change the symbols P to Change the symbols P to for osmotic pressure for osmotic pressure

and (n/V) to cand (n/V) to c

The resulting equation for Osmotic Pressure is The resulting equation for Osmotic Pressure is

= c R T R = .082 = c R T R = .082 L x atmL x atm

mol x Kmol x K


OsmosisOsmosis

isotonicisotonic similar concentrations of solutes similar concentrations of solutes

hypotonic hypotonic solution with lower solute concentrationssolution with lower solute concentrations

hypotonic hypotonic solution with higher solute concentrationssolution with higher solute concentrations

reverse osmosisreverse osmosis using pressure to purify water. using pressure to purify water.


ColloidsColloids


Colloids Colloids are classified according to the state of are classified according to the state of dispersed phase and the dispersing medium.dispersed phase and the dispersing medium.

Hydrophobic ‘Hydrophobic ‘water fearing’ weak attractive forces water fearing’ weak attractive forces between water and surface of colloidal particles.between water and surface of colloidal particles.

Hydrophilic Hydrophilic ‘water loving’ are strongly attracted to ‘water loving’ are strongly attracted to the water moleculesthe water molecules

EmulsionsEmulsions are colloidal dispersions of one liquid in are colloidal dispersions of one liquid in another by using an another by using an emulsifying agentemulsifying agent such as such as protein or soap.protein or soap.


Surfactants Surfactants are emulsifying agentsare emulsifying agents

Hydrocarbon end soluble in oilHydrocarbon end soluble in oil

Polar end soluble in waterPolar end soluble in water

chapter 14: solutions and their properties solution homogeneous mixture of two or more substances...

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