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Solutions Chapter 15 & 16 Chemistry


Do Now

ďƒ˜ Create a three circle venn diagram that

compares and contrasts the 3 examples of mixtures (Solutions, Suspensions, Colloids)

Making solutions Solute: Dissolved particles

Solvents: The thing that does the dissolving.

Solution: A homogenous mixture that contains solutes dissolved in solvents.

Uniform throughout

Solutions  Homogeneous  0.01 – 1 nm solute particle; atoms, ions,

molecules  Does not separate on standing  Cannot be separated by filtration  No light scattering

Colloids  Heterogeneous  1 – 1000 nm dispersed particles; particles

or large molecules  Does not separate on standing  Cannot be separated by filtration  Scatters light (Tyndall Effect)

Suspension  Heterogeneous  Over 1000 nm

suspended particles; large particles or aggregates  Particles settle out  Can be separated by filtration  May scatter light, but not transparent

Colloids  First discovered:


 The particles are spread throughout the

dispersion medium (solid, liquid, gas).  Cloudy or milky in appearance when

concentrated  Look clear or almost clear when diluted

Colloids  Dispersed Phase 

State of matter that is in between the outer edge. Interior phase

 Dispersed Medium 

Phase of matter it appears to be in

Tyndall Effect

Brownian Motion 

Chaotic Movement

Flashes of light, or scintillations, are seen when colloids are studied under a microscope. 

Caused by particles reflecting and scattering the light more erratically.

Coagulation 

Colloidal particles tend to stay suspended because they become charged by absorbing ions from the dispersing medium onto their surface. 

Some positively charged, some negatively charged.

Destroying a colloidal system 

Adding ions having a charge opposite to that of the colloidal particles • They neutralize the charged colloidal particles • Particles clump together to form heavier aggregates and precipitate from the dispersion

Emulsions  A colloidal dispersion of a liquid in a liquid. 

Emulsifying agent is essential for the formation of an emulsion • Ex. Oils and greases are not soluble in water • Adding soap or detergent to water allows for mixtures to mix

• Mayonnaise 

Heterogeneous mixture of oil and vinegar • Egg yolk acts as emulsifying agent

Electrolytes ďƒ˜ A compound that

conducts electric current when it is in an aqueous solution or in the molten state. ď Ź

All ionic compounds (dissociate into ions)

Solvation Process Process by which the positive and negative ions of an ionic solid become surrounded by solvent molecules.

Nonelectrolytes  A compound that does not conduct an

electric current in either aqueous solution or the molten state.  Many molecular compounds are not electrolytes (no ions). 

Sugar (sucrose), rubbing alcohol (2-propanol)

Review on your own (Chp. 15)  Surface Tension  Hydrogen Bonding  Vapor Pressure  Hydrates  Deliquescents

Solutions Chapter 16 Sections 1 - 4

Using the pictures as a model….  Come up with a definition of the following

terms:   

Saturated Unsaturated Supersaturated

A little earth science never hurts anyone. Another example that you learned everything in Earth Science already 

Solubility Curves Saturated



Factors Affecting Solubility  Temperature 

Most solids • Substance solubility increases with Temperature Mineral deposits a result of cooling of solution of mineral water.

Cooling water holds less minerals

Factors Affecting Solubility  Pressure  

Little affect on solids and liquids Strong influence on Gases

Molarity Problem: Calculate the molarity of a solution containing 100 g of KCl in 500 ml of water. moles M= liters

1.34 moles Molarity = .5 liters

K 1 x 39.1 = 39.1 Cl 1 x 35.5 = 35.5 74.6 100 g

1 mol 74.6 g

= 1.34 mol

2.68 M

Molarity ďƒ˜ The number of moles of solute in one liter

of solution ďƒ˜ Molarity = # of moles of solute

---------------------------# of liters of solution Units - M

Percent by Mass  Percent by mass of a solute in solution is

the number of grams of solute dissolved in 100 grams of solution. 

% (m/m) = mass of solute / mass of solution x 100 Mass of solute + Mass of solvent

% (v/v) = volume of solute / volume of solution x 100 volume of solute + volume of solvent

% Mass and % Volume Products


Colligative Properties  Property that depends on the number of

solute particles but is independent of their nature

 Adding Nonvolatile

solute (little tendency to

become a gas under existing conditions)   

Lowers the vapor pressure of solvent Lowers the freezing point of solution Raises the boiling point of solution

Vapor-Pressure Lowering 

Vapor pressure 

Pressure exerted by a vapor that is in dynamic equilibrium with its liquid in a closed system.

Volatility  

Ease of vaporization Glucose, sodium chloride • When dissolved in a solvent, the vapor pressure of the solution is lower than the vapor pressure of the pure solvent.

Colligative Property: Vapor Pressure lowering

Molality ďƒ˜ The concentration of a solution expressed

in moles of solute per kilogram of solvent ďƒ˜ Molality = # of moles solute

--------------------------mass of solvent (kg) Units - m

Freezing Point Depression  

A colligative property The difference in temperature between the freezing point of a solution and the freezing point of the pure solvent. ΔTf = Kf x d.f. x m ΔTf = Freezing point depression m = molality

Kf = molal freezing-point depression constant For Water (1.86°C/m) d.f. = Dissociation Factor (covalents it is one, Ionic it depends on ions it dissociates into)

Boiling Point Elevation 

Boiling point = vapor pressure equals atmospheric pressure 

Change in either causes a change in boiling point

Boiling point elevation of 1 molal solution of any molecular solute in water is 0.512 degrees Celsius ΔTb = Kb x

d.f. x m

ΔTb = Boiling Point Elevation m = molality

Kb = molal boiling-point elevation constant For Water (0.512°C/m) d.f. = Dissociation Factor (covalents it is one, Ionic it depends on ions it dissociates into)

Formation of a Solution Solvation Hydration

Solvent H2O Cl- Na+ salt Na+ Clsolute

Na+ Cl-

Dissolved solute

Solubility Rules

Solutions (Chapter 15-16)