General chemistry
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General Chemistry. M. R. Naimi-Jamal Faculty of Chemistry Iran University of Science & Technology. فصل دوازدهم :. م حلول ها. Contents. 1 2 -1 Types of Solutions: Some Terminology 1 2 -2 Solution Concentration 1 2 -3 Intermolecular Forces and the Solution Process

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General Chemistry

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General chemistry

General Chemistry

M. R. Naimi-Jamal

Faculty of Chemistry

Iran University of Science & Technology


General chemistry

فصل دوازدهم:

محلول ها


Contents

Contents

12-1Types of Solutions: Some Terminology

12-2Solution Concentration

12-3Intermolecular Forces and the Solution Process

12-4Solution Formation and Equilibrium

12-5Solubilities of Gases

12-6Vapor Pressure of Solutions

12-7Osmotic Pressure


Contents1

Contents

12-8Freezing-Point Depression and Boiling-Point Elevation of Nonelectrolyte solutions.

12-9Solutions of Electrolytes

12-10Colloidal Mixtures

Focus on Chromatography


Types of solution some terminology

Types of Solution: Some Terminology

  • Solutions are homogeneous mixtures

    • Uniform throughout.

  • Solvent

    • Determines the state of matter in which the solution exists.

    • Is the largest component.

  • Solute

    • Other solution components said to be dissolved in the solution.


Table 14 1 some common solutions

Table 14.1 Some Common Solutions


Solution concentration

Solution Concentration.

  • Mass percent. (m/m)

  • Volume percent. (v/v)

  • Mass/volume percent. (m/v)

  • Isotonic saline is prepared by dissolving 0.9 g of NaCl in 100 mL of water and is said to be:

    0.9% NaCl (mass/volume)


10 ethanol solution v v

10% Ethanol Solution (v/v)


Ppm ppb and ppt

ppm, ppb and ppt

  • Very low solute concentrations are expressed as:

    ppm:parts per million (g/g, mg/L)

    ppb:parts per billion(ng/g, g/L)

    ppt:parts per trillion(pg/g, ng/L)

    note that 1.0 L x 1.0 g/mL = 1000 g

    ppm, ppb, and ppt are properly m/m or v/v.


Mole fraction and mole percent

Mole Fraction and Mole Percent

Amount of component i (in moles)

Total amount of all components (in moles)

 =

1 + 2 + 3 + …n = 1

Mole % i = ix 100%


Molarity and molality

Molarity and Molality

Amount of solute(in moles)

Volume of solution (in liters)

Molarity (M) =

Amount of solute(in moles)

Mass of solvent (in kilograms)

Molality (m) =


Intermolecular forces and the solution process

Intermolecular Forces and the Solution Process

ΔHc

ΔHb

ΔHa


Intermolecular forces in mixtures

Intermolecular Forces in Mixtures

  • Magnitude of ΔHa, ΔHb, and ΔHc depend on intermolecular forces.

  • Ideal solution

    • Forces are similar between all combinations of components.

ΔHsoln = 0


Ideal solution

Ideal Solution

benzene

toulene


Non ideal solutions

Non-ideal Solutions

  • Adhesive forces greater than cohesive forces.

ΔHsoln < 0


Non ideal solutions1

Non-ideal Solutions

  • Adhesive forces are less than cohesive forces.

  • At the limit these solutions are heterogeneous.

ΔHsoln > 0

aceton

CS2


Ionic solutions

Ionic Solutions


General chemistry

Dissolution of NaCl


Hydration energy

Hydration Energy

NaCl(s) → Na+(g) + Cl-(g)ΔHlattice > 0

Na+(g) + xs H2O(l) → Na+(aq)ΔHhydration < 0

Cl-(g) + xs H2O(l) → Cl-(aq)ΔHhydration < 0

For NaCl: ΔHsoln > 0 but ΔGsolution < 0


Solution formation and equilibrium

Solution Formation and Equilibrium

saturated


Solubility curves

Solubility Curves

Supersaturated Unsaturated


Solubility of gases

Solubility of Gases

  • Most gases are less soluble in water as temperature increases.

  • In organic solvents the reverse is often true.


Henry s law

Henry’s Law


Henry s law1

C

23.54 mL

= 23.54 ml N2/atm

k =

=

Pgas

1.00 atm

C

100 mL

= 4.25 atm

Pgas =

=

k

23.54 ml N2/atm

Henry’s Law

C = k Pgas

  • Solubility of a gas increases with increasing pressure.


Vapor pressures of solutions

Vapor Pressures of Solutions

  • Roault, 1880s.

    • Dissolved solute lowers vapor pressure of solvent.

    • The partial pressure exerted by solvent vapor above an ideal solution is the product of the mole fraction of solvent in the solution and the vapor pressure of the pure solvent at a given temperature.

      PA = A PA°


Example

Example

Predicting vapor pressure of ideal solutions.

The vapor pressures of pure benzene and toluene at 25°C are 95.1 and 28.4 mm Hg, respectively. A solution is prepared in which the mole fractions of benzene and toluene are both 0.500. What are the partial pressures of the benzene and toluene above this solution? What is the total vapor pressure?

Balanced Chemical Equation:

  • Pbenzene = benzene P°benzene = (0.500)(96.1 mm Hg) = 47.6 mm Hg

  • Ptoluene = toluene P°toluene = (0.500)(28.4 mm Hg) = 14.2 mm Hg

  • Ptotal = Pbenzene + Ptoluene = 61.8 mm Hg


Example1

Example

Calculating the Composition of Vapor in Equilibrium with a Liquid Solution.

What is the composition of the vapor in equilibrium with the benzene-toluene solution?

Partial pressure and mole fraction:

  • benzene =Pbenzene/Ptotal = 47.6 mm Hg/61.89 mm Hg = 0.770

  • toluene =Ptoluene/Ptotal = 14.2 mm Hg/61.89 mm Hg = 0.230


Liquid vapor equilibrium

Liquid-Vapor Equilibrium


Fractional distillation

Fractional Distillation


Fractional distillation1

Fractional Distillation


Non ideal behavior

Non-ideal behavior


Osmotic pressure

Osmotic Pressure


Osmotic pressure1

n

π = RT

V

Osmotic Pressure

For dilute solutions of electrolytes:

πV = nRT

= M RT


Osmotic pressure2

Osmotic Pressure

Hypertonic > 0.92% m/V

crenation

Isotonic Saline 0.92% m/V

Hypotonic > 0.92% m/V

rupture


Reverse osmosis desalination

Reverse Osmosis - Desalination


Freezing point depression and boiling point elevation of nonelectrolyte solutions

Freezing-Point Depression and Boiling Point Elevation of Nonelectrolyte Solutions

  • Vapor pressure is lowered when a solute is present.

    • This results in boiling point elevation.

    • Freezing point is also effected and is lowered.

  • Colligative properties.

    • Depends on the number of particles present.


Vapor pressure lowering

Vapor Pressure Lowering

ΔTf = -Kfx m

ΔTb = -Kbx m


Practical applications

Practical Applications


Solutions of electrolytes

Solutions of Electrolytes

ΔTf = -Kf. m

  • Svante Arrhenius

    • Nobel Prize 1903

    • Ions form when electrolytes dissolve in solution.

    • Explained anomalous colligative properties

      Compare 0.0100 m aqueous urea to 0.0100 m NaCl (aq)

      ΔTf = -Kfx m = -1.86°C m-1x 0.0100 m = -0.0186°C

      Freezing point depression for NaCl is -0.0361°C


Van t hoff

van’t Hoff

measured ΔTf

0.0361°C

i = == 1.98

expected ΔTf

0.0186°C

π = -i x M x RT

ΔTf = -i x Kfx m

ΔTb = -i x Kbx m


Interionic interactions

Interionic Interactions

  • Arrhenius theory does not correctly predict the conductivity of concentrated electrolytes.


Debye and h ckel

Debye and Hückel

  • 1923

    • Ions in solution do not behave independently.

    • Each ion is surrounded by others of opposite charge.

    • Ion mobility is reduced by the drag of the ionic atmosphere.


Colloidal mixtures

Colloidal Mixtures


Colloids

Colloids

  • Particles of 1-1000 nm size

    • Nanoparticles of various shapes: rods, discs, spheres

    • Particles can remain suspended indefinitly

      • Milk is colloidal

  • Increasing ionic strength can cause precipitation


Dialysis

Dialysis


Focus on chromatography

Focus on Chromatography

Stationary Phase

silicon gum

alumina

silica

Mobile Phase

solvent

gas


Chromatography

Chromatography


Chapter 12 questions

Chapter 12 Questions

8, 14, 15, 22, 23, 29, 36, 46, 49, 66, 73, 81, 85


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