Top Banner
perties of Solutions: Ways of Expressing Concentra perties of Solutions: Ways of Expressing Concentra Weight percentage = mass of component in solution total mass of solution Parts per million (ppm) = mass of component in solution total mass of solution A solution is made containing 6.9 g NaHCO 3 per 100 g water. What is the weight percentage of solute in the solution? A 2.5 g sample of ground water was found to contain 5.4 micrograms of Zn 2+ . What is the concentration of Zn 2+ in ppm 6.9g 106.9 g x 100 = 6.5% x 100 x 10 6 5.4 x 10 -6 2.5 g x 10 6 ppm = Wt % of component = = 2.2ppm
39

Properties of Solutions: Ways of Expressing Concentrations Weight percentage = mass of component in solution total mass of solution Parts per million (ppm)

Mar 27, 2015

Download

Documents

Michael Willis
Welcome message from author
This document is posted to help you gain knowledge. Please leave a comment to let me know what you think about it! Share it to your friends and learn new things together.
Transcript
Page 1: Properties of Solutions: Ways of Expressing Concentrations Weight percentage = mass of component in solution total mass of solution Parts per million (ppm)

Properties of Solutions: Ways of Expressing ConcentrationsProperties of Solutions: Ways of Expressing Concentrations

Weight percentage = mass of component in solution

total mass of solution

Parts per million (ppm) = mass of component in solution

total mass of solution

A solution is made containing 6.9 g NaHCO3 per 100 g water. What is the weight percentage of solute in the solution? A 2.5 g sample of ground water was found to contain 5.4 micrograms of Zn2+. What is the concentration of Zn2+ in ppm

6.9g

106.9 gx 100 = 6.5%

x 100

x 106

5.4 x 10-6 2.5 g

x 106ppm =

Wt % of component =

= 2.2ppm

Page 2: Properties of Solutions: Ways of Expressing Concentrations Weight percentage = mass of component in solution total mass of solution Parts per million (ppm)

Mole fraction, Molarity , and MolalityMole fraction, Molarity , and MolalityMole fraction of a component = Moles component

Total moles of all components

Calculate the mole fraction of HCl in a solution of HCl containing 36% HCl by weight.

36 g HCl1 mole HCl36.5 g HCl

= 0.99 mol HCl

64 g H2O1 mole H2O

18 g H2O = 3.6 mol H2O

XHCl = Mole HCl

Moles HCl + H2O= 0.99 mol

4.6 mol= 0.22

Page 3: Properties of Solutions: Ways of Expressing Concentrations Weight percentage = mass of component in solution total mass of solution Parts per million (ppm)

Mole fraction, Molarity , and MolalityMole fraction, Molarity , and MolalityMolarity = Molarity = Moles of soluteMoles of solute

Liters of solutionLiters of solution

What is the molarity of an ascorbic acid solution (C6H8O6) prepared by dissolving1.80 grams in enough water to make 125 mL of solution. How many milliliters of thissolution contain 0.0100 mol ascorbic acid.

1.80 g C6H8O6

1 mol C6H8O6

176 g C6H8O6

= 0.0102 mol C6H8O6

Molarity = 0.0102 mol C6H8O6

.125 L soln= 0.0818 M

Page 4: Properties of Solutions: Ways of Expressing Concentrations Weight percentage = mass of component in solution total mass of solution Parts per million (ppm)

Mole fraction, Molarity , and MolalityMole fraction, Molarity , and Molality

Molality = moles of soluteMolality = moles of solute

Kg of solventKg of solvent

What is the molality of a solution made by dissolving 5.0 g of toluene (C7H8) in 25 g of benzene (C6H6)?

5.0 g C7H8 1 mol C7H8

92 g C7H8

= 0.054 mol C7H8

Molality = 0.054 mol C7H8

.025 kg C6H6

= 2.2 m

Page 5: Properties of Solutions: Ways of Expressing Concentrations Weight percentage = mass of component in solution total mass of solution Parts per million (ppm)

Properties of Solutions: The Solution ProcessProperties of Solutions: The Solution Process

Na+Cl-

-

-+

+

+

+

-

-

Cl-

Na+

Solvation or hydration

Na+

Na+

Na+

Cl-

Cl-

Cl-

Cl-

Na+

Cl-

Page 6: Properties of Solutions: Ways of Expressing Concentrations Weight percentage = mass of component in solution total mass of solution Parts per million (ppm)

Properties of Solutions: The Solution ProcessProperties of Solutions: The Solution ProcessEnergy Changes and Solution FormationEnergy Changes and Solution Formation

Hsoln = H1 + H2

+ H3

Solute-solute interactions

Solvent-solvent interactions

Solute-solvent interactions

Page 7: Properties of Solutions: Ways of Expressing Concentrations Weight percentage = mass of component in solution total mass of solution Parts per million (ppm)

Properties of Solutions: The Solution ProcessProperties of Solutions: The Solution ProcessEnergy Changes and Solution FormationEnergy Changes and Solution Formation

The overall change in enthalpy can be exo- or endothermic

NaOH: Hsoln = -44.48 NH4OH: Hsoln

= 26.4

This explains why “like dissolves like”

Page 8: Properties of Solutions: Ways of Expressing Concentrations Weight percentage = mass of component in solution total mass of solution Parts per million (ppm)

Properties of Solutions: Solution Formation, SpontaneityProperties of Solutions: Solution Formation, Spontaneityand Disorder…and Disorder…WHY DOES THIS STUFF DISSOLVEWHY DOES THIS STUFF DISSOLVE??

bp = 77 bp = 69

London dispersion forces

Little energy is exchanged

Page 9: Properties of Solutions: Ways of Expressing Concentrations Weight percentage = mass of component in solution total mass of solution Parts per million (ppm)

Properties of Solutions: Solution Formation, SpontaneityProperties of Solutions: Solution Formation, Spontaneityand Disorder…and Disorder…WHY DOES THIS STUFF DISSOLVEWHY DOES THIS STUFF DISSOLVE??

Processes in which the energy content of the system decreases tend to occurspontaneously.

Processes in which the disorder of the system increases tend to occur spontaneously

When molecules of different types are brought together, an increase in disorder occurs spontaneously unless the molecules are restrained sufficiently by strong intermolecular forces. Salt does not dissolve in gasoline because strong forces are holding the Na+ andCl- ions together and the intermolecular forces associated with nonpolar substances is not sufficient to dislodge them.

Page 10: Properties of Solutions: Ways of Expressing Concentrations Weight percentage = mass of component in solution total mass of solution Parts per million (ppm)

Properties of Solutions: Saturated Solutions and SolubilitycProperties of Solutions: Saturated Solutions and SolubilitycAs solid solute begins to dissolve in a solvent, the concentrations of solute particlesin solution increases, so the chances of their colliding with the surface of the solidincreases. This may lead to crystallization.

Solute + Solvent Solutiondissolve

crystallize

Saturated: a solution with undissolvedsolute

Supersaturated: a solution which contains a greater amount of solute than needed toform a saturated solution

Page 11: Properties of Solutions: Ways of Expressing Concentrations Weight percentage = mass of component in solution total mass of solution Parts per million (ppm)

Properties of Solutions: Factors Affecting SolubilityProperties of Solutions: Factors Affecting Solubility

•As a rule, solubility increases with increasing molecular mass

•Polar liquids tend to dissolve in polar solvents. If the dissolve they are miscible.If they do not dissolve they are immiscible

Page 12: Properties of Solutions: Ways of Expressing Concentrations Weight percentage = mass of component in solution total mass of solution Parts per million (ppm)

Properties of Solutions: Factors Affecting SolubilityProperties of Solutions: Factors Affecting SolubilityHydrogen-boning interactions between solute and solvent may lead to high solubility

Ethanol and ethanol Ethanol and water

Because of H-bonding, solute-solute, solvent-solvent, and solute-solventinteractions are not appreciably different.

There is no significant change in the environment

Page 13: Properties of Solutions: Ways of Expressing Concentrations Weight percentage = mass of component in solution total mass of solution Parts per million (ppm)

However, the numbers carbon atoms in an alcohol does effect it solubility in water.

Properties of Solutions: Factors Affecting SolubilityProperties of Solutions: Factors Affecting Solubility

As the length of the chain increases, the OH groups decrease leading to a decrease in solubility

Page 14: Properties of Solutions: Ways of Expressing Concentrations Weight percentage = mass of component in solution total mass of solution Parts per million (ppm)

Glocuse has 5-OH groups on a six carbon framework which makes themolecule fairly soluble in water

Properties of Solutions: Factors Affecting SolubilityProperties of Solutions: Factors Affecting SolubilitySubstances with similar intermolecular attractive forces tend to be solublein one another….LIKE DISSOLVES LIKE

Page 15: Properties of Solutions: Ways of Expressing Concentrations Weight percentage = mass of component in solution total mass of solution Parts per million (ppm)

Properties of Solutions: Factors Affecting SolubilityProperties of Solutions: Factors Affecting SolubilitySubstances with similar intermolecular attractive forces tend to be solublein one another….LIKE DISSOLVES LIKE

Predict whether each of the following substances is more likely to dissolve in carbontetrachloride or water: C7H16. NaHCO3, HCl

Page 16: Properties of Solutions: Ways of Expressing Concentrations Weight percentage = mass of component in solution total mass of solution Parts per million (ppm)

Pressure EffectsPressure EffectsThe solubility of a gas in any solvent is increased as the pressure of the gas over the solvent increasesBy contrast the solubility of solids and liquids are not appreciable affected by pressure.

Page 17: Properties of Solutions: Ways of Expressing Concentrations Weight percentage = mass of component in solution total mass of solution Parts per million (ppm)

The relationship between pressure and solubility is expressed by Henry’s Law:

Cg = kPg where Cg is the solubility of the gas in the solution phase, Pg is the partial pressure of the gas over the solution, and k is a Henry’s law constant which differs from one solute-solvent pair to another.

For example the solubility of N2 gas in water at 25 ° C and 0.78 atm. is 5.3 x 10-4 Mk = 5.3 x 10-4 M/0.78 = 6.8 x 10-4 mol/l-atm. Assume that the partial pressure of the N2 is doubled, Henry’s law, Cg = kPg predicts that the solubility will also double.

Cg = kPg

Cg = (6.8 x 10-4 mol/l-atm)(1.56 atm) Cg = 0.0011

Page 18: Properties of Solutions: Ways of Expressing Concentrations Weight percentage = mass of component in solution total mass of solution Parts per million (ppm)

Temperature EffectsTemperature Effects

In general, the solubility of gases decreases as temperature increases

Page 19: Properties of Solutions: Ways of Expressing Concentrations Weight percentage = mass of component in solution total mass of solution Parts per million (ppm)

Temperature EffectsTemperature Effects

In general, the solubility of of ionic compounds, solids, normally increases as the temperature increases.

Page 20: Properties of Solutions: Ways of Expressing Concentrations Weight percentage = mass of component in solution total mass of solution Parts per million (ppm)

Colligative PropertiesColligative PropertiesThe increase or decrease of of the concentrations and not the kinds of particles in solutions can effect certain physical properties of solutions

•Freezing point depression of a solution•Boiling point elevation of a solution•vapor pressure; Raoult’s Law•Osmotic pressure

Colligative means “depending upon the collection”; colligative properties depend upon the collective effect of the

number of solute particles

Page 21: Properties of Solutions: Ways of Expressing Concentrations Weight percentage = mass of component in solution total mass of solution Parts per million (ppm)

Colligative PropertiesColligative Properties

Lowering the Vapor Pressure: TRY EXPLAINING THIS ONE!!

Page 22: Properties of Solutions: Ways of Expressing Concentrations Weight percentage = mass of component in solution total mass of solution Parts per million (ppm)

Lowering the Vapor Pressure: Explaining How it is Done!!

A non-volatile solute added to a solvent reduces the capacity of thesolvent molecules in the liquid phase to move into the gas phase

The extent to which a nonvolatile solute lowers the vapor pressureis proportional to the concentration

Page 23: Properties of Solutions: Ways of Expressing Concentrations Weight percentage = mass of component in solution total mass of solution Parts per million (ppm)

Raoult’s Law: Calculating the vapor Raoult’s Law: Calculating the vapor pressure of a solution based upon the pressure of a solution based upon the amount of solute being added to the amount of solute being added to the

solution.solution.

PA = XAPA° Where PA is the vapor pressure of the solution, XA is the

mole fraction of solventsolvent, and P°A is the vapor pressure of the pure

solvent

Page 24: Properties of Solutions: Ways of Expressing Concentrations Weight percentage = mass of component in solution total mass of solution Parts per million (ppm)

Colligative Properties are the first evidence that salts break up into ions.

Xa = Mole of solvent

Moles of solvent + moles of solute x ii

If 10g of MgClIf 10g of MgCl2 2 is added to 100ml of is added to 100ml of

HH22O at 23O at 23ºC, ºC, what would be the vapor what would be the vapor

pressure. The vapor pressure for water pressure. The vapor pressure for water at this temperature is 21.07 torr.at this temperature is 21.07 torr.

Page 25: Properties of Solutions: Ways of Expressing Concentrations Weight percentage = mass of component in solution total mass of solution Parts per million (ppm)

What is the vapor pressure of a solution made with 1 mol of Benzene and 2 mol of toluene at 20ºC and the mole fraction of the vapor? Benzene = 75 torr and Toluene = 22 torr

P A = XA P°A + P B = XB P°B

Page 26: Properties of Solutions: Ways of Expressing Concentrations Weight percentage = mass of component in solution total mass of solution Parts per million (ppm)

Properties of Solutions:Boiling Point Properties of Solutions:Boiling Point Elevation and Freezing Point DepressionElevation and Freezing Point Depression

Page 27: Properties of Solutions: Ways of Expressing Concentrations Weight percentage = mass of component in solution total mass of solution Parts per million (ppm)

Because nonvolatile solutes lower the vapor pressure of a solution, a higher temperature is required to cause the

solution to boil.Because the vapor pressure of the solution is lower than that of the solvent at all temps, in accordance to Raoult’s Law, the higher temperature is required to attain a vapor

pressure of 1 atm. Tb = Kb m , where Tb is directly proportional to the

number of solute particles per moles of solvent molecules, and Kb is called the molal boiling-point-elevation constant

For example, the Kb of water is 0.52 °C/m; therefore a 1m solution of sucrose or any other aqueous solution that is 1m in nonvolatile solute particles will boil at a temperature of

0.52°C higher than pure water.

Boiling Point ElevationBoiling Point Elevationand Freezing Point Depressionand Freezing Point Depression

Page 28: Properties of Solutions: Ways of Expressing Concentrations Weight percentage = mass of component in solution total mass of solution Parts per million (ppm)

The freezing point corresponds to the temperature at which the vapor pressures of the solid and liquid phases are the same. The freezing point of a solution is lowered because the solute is not normally soluble in the solid phase of the solvent

If the solute is nonvolatile, the vapor pressure of the solution is reduced in proportion to the mole fraction of solute.

Tf = Kf m , where Tf is directly proportional to the number of solute particles per moles of solvent molecules, and Kf is called the molal-freezing-point-depression constant

For example, the Kf of water is 1.86 °C/m; therefore a 0.5 m solution of NaCl or any other aqueous solution that is 1m in nonvolatile solute particles will freeze at a temperature of 1.86 °C lower than pure water.

Page 29: Properties of Solutions: Ways of Expressing Concentrations Weight percentage = mass of component in solution total mass of solution Parts per million (ppm)

Calculate the freezing point and the boiling point of a solution of 100 g of ethylene glycol (C2H6O2), antifreeze in

900 g of H2O.

m = Moles C2H6O2

Kilograms H2O

100 g C2H6O2

.900 kg H2O1 mol C2H6O2

62.0 g C2H6O2

= 1.79 m

Tf = Kf m = 1.86 °C m

(1.79 m ) = 3.33 °C

Therefore freezing point = -3.33 °C

=

Tb = Kbm = .52 °C m

(1.79 m ) = 100.93 °C

Page 30: Properties of Solutions: Ways of Expressing Concentrations Weight percentage = mass of component in solution total mass of solution Parts per million (ppm)

Adrenaline is the hormone that triggers the release of extra glucose molecules in times of stress or emergency. A solution of 0.64 g of adrenaline in 36.0 g of CCl4 elevates the boiling pt. by 0.49ºC. What is the molar mass?

ΔTb = Kbm KB for adrenaline is 3.63

0.49 = 3.63 (.64g mole )

xg

.036kg

Page 31: Properties of Solutions: Ways of Expressing Concentrations Weight percentage = mass of component in solution total mass of solution Parts per million (ppm)

Properties of Solutions:OsmosisProperties of Solutions:Osmosis

The net movement of solvent is always toward the more concentratedsolution

The pressure required to prevent osmosis is called theosmotic pressure, , of the solution, where = MRT

Page 32: Properties of Solutions: Ways of Expressing Concentrations Weight percentage = mass of component in solution total mass of solution Parts per million (ppm)

Hypertonic Solution Hypotonic Solution

Properties of Solutions:OsmosisProperties of Solutions:Osmosis

Page 33: Properties of Solutions: Ways of Expressing Concentrations Weight percentage = mass of component in solution total mass of solution Parts per million (ppm)

Properties of Solutions:OsmosisProperties of Solutions:OsmosisSample problem: The average osmotic pressure of blood is 7.7 atm. At 25°C. What concentration of glucose (C6H12O6) would be isotonic with blood?

Page 34: Properties of Solutions: Ways of Expressing Concentrations Weight percentage = mass of component in solution total mass of solution Parts per million (ppm)

Lysozyme is an enzyme that breaks bacterial cell walls. a solution containing 0.150 g of this enzyme in 210 mL of solution has an osmotic pressure of 0.953 torr at 25ºC. What is the molar mass of Lysozyme?

π = MRT

.953 = .150g mole 62.3 298

xg

.21L

Page 35: Properties of Solutions: Ways of Expressing Concentrations Weight percentage = mass of component in solution total mass of solution Parts per million (ppm)

Properties of Solutions:ColloidsProperties of Solutions:Colloids

Suspensions that are the dividing Line Between Solutions and Heterogeneous Mixtures

Tyndell effect: a scattering of light by colloidal particles

Page 36: Properties of Solutions: Ways of Expressing Concentrations Weight percentage = mass of component in solution total mass of solution Parts per million (ppm)

Properties of Solutions:ColloidsProperties of Solutions:Colloids

Hydrophilic and Hydrophobic Colloids

The most important colloids are those in which the dispersing medium is waterThe most important colloids are those in which the dispersing medium is water

Hydrophilic colloids are kept in suspension by interactionwith surrounding water molecules

Page 37: Properties of Solutions: Ways of Expressing Concentrations Weight percentage = mass of component in solution total mass of solution Parts per million (ppm)

Properties of Solutions:ColloidsProperties of Solutions:Colloids

Hydrophilic and Hydrophobic Colloids

The most important colloids are those in which the dispersing medium is waterThe most important colloids are those in which the dispersing medium is water

Hydrophobic colloids can be stabilized in water by the adsorption of ions ontotheir surface

Page 38: Properties of Solutions: Ways of Expressing Concentrations Weight percentage = mass of component in solution total mass of solution Parts per million (ppm)

Properties of Solutions:ColloidsProperties of Solutions:Colloids

Hydrophilic and Hydrophobic Colloids

The most important colloids are those in which the dispersing medium is waterThe most important colloids are those in which the dispersing medium is water

Page 39: Properties of Solutions: Ways of Expressing Concentrations Weight percentage = mass of component in solution total mass of solution Parts per million (ppm)

Pa = Xa Paº

Xa= moles of solvent

moles of solvent + moles of solute x i

ΔTb = Kbm i

ΔTf = Kfm i

π = MRTi