Download Concentration of solutions

Solute
Solvent
Example
Gas
Gas
Liquid
Gas
Liquid
Liquid
Oxygen in nitrogen
CO2 in H2O (carbonated beverages)
Alcohol in water, ethylene glycol in
water (antifreeze), acetic acid in
water (vinegar)
Liquid
Solid
Hg in Ag and Sn (dental amalgam)
Solid
Solid
Liquid
Solid
Sugar in water, ocean water (salt in water)
Copper in nickel (Monel™ alloy)
Page 402 in your text
Heterogeneous mixtures are suspensions and
colloids.
Brownian motion is the erratic movement of
colloid particles. The Tyndall effect (named
after John Tyndall) is when light is scattered by
colloidal particles dispersed in a transparent
medium. For example: car
headlights in fog.
http://www.chm.bris.ac.uk/webprojects2002/pdavies/Ty
ndall.jpg
Solutions
Homogeneous
Particle size: 0.01- 1
nm; can be atoms,
ions, molecules
Colloids
Heterogeneous
Particle size: 1-1000
nm, dispersed; can be
aggregates of large
molecules
Do not separate on
Do not separate on
standing
standing
Cannot be separated Cannot be separated
by filtration
by filtration
Scatter light (Tyndall
Do not scatter light
effect)
Suspensions
Heterogeneous
Particle size: over
1000 nm, suspended;
can be large particles
or aggregates
Particles settle out if
not constantly stirred
Can be separated by
filtration
May scatter light, but
are not transparent
Page 404 in your text
Class of colloid
Sol
Gel
Liquid emulsion
Foam
Phases
Solid dispersed in liquid
Solid network extending
throughout liquid
Liquid dispersed in liquid
Gas dispersed in liquid
Solid aerosol
Solid dispersed in gas
Liquid aerosol
Liquid dispersed in gas
Solid emulsion
Liquid dispersed in solid
Example
Paints, mud
Gelatin
Milk, mayonnaise
Shaving cream,
whipped cream
Smoke, airborne
particulate matter,
auto exhaust
Fog, mist, clouds,
aerosol spray
Cheese, butter
Page 404 in your text
Solutes are classified
according to the
extent they dissociate
into ions in aqueous
solutions.
• Strong electrolyte:
substance that
dissolves in water to
give a solution that
conducts electricity.
(i.e. salt – NaCl)
Weak electrolyte: less than
50% of dissolved solute
exists as ions.
(i.e. – acetic acid[vinegar])
• Nonelectrolyte: < 0.01% exists as ions; does
not conduct electricity when solute is
dissolved in water. (i.e. sugar – C12H22O11)
Factors that affect the rate of
dissolution
–increasing the surface area of
the solute
–stirring
–heating the solvent
• Solubility is the maximum quantity of
solute that can be dissolved in a given
quantity of solvent at a particular
temperature. It is usually expressed in
g of solute per 100 g of solvent at a
given temperature.
• The three interactions that determine
the solubility are solute-solute, solutesolvent, and solvent-solvent
interactions.
Temperature
effects on
solubility
http://galileo.phys.virginia.edu/educa
tion/outreach/8thgradesol/images/so
lubility.jpg
• Solution equilibrium is the physical state in which
the opposing processes of dissolution and
crystallization of a solute occur at equal rates.
• Saturated solution: a solution that contains the
maximum amount of dissolved solute.
• Unsaturated solution: a solution that contains
less than a saturated solution under the current
conditions.
• Supersaturated solution: a solution that contains
more dissolved solute than a saturated solution
contains under the same conditions.
• Nature of solute and solvent (polarity, etc.)
Solute-solvent interactions - “like dissolves
like”
• Temperature (for gases an increase in T
decreases solubility). For the majority of solids
in liquids, increasing T increases their
solubility. The degree of solubility can differ
greatly and in some cases, even decrease a
solid’s solubility.
• pressure (for solids and liquids has no effect;
for gases an increase in P increases solubility)
gas + solvent  solution
Henry’s Law
the solubility of a gas in a liquid is
Directly proportional to the partial
pressure of that gas on the surface of
the liquid.
S1 = S2
P1 P2
In carbonated beverages forcing it into solution at
pressure of 5-10 atm increases CO2 solubility. The
containers are then sealed. When opened, the CO2 gas
escapes as the pressure returns to 1 atm. The rapid
escape of a gas from a liquid in which it is dissolved is
called effervescence.
• The net amount of heat energy absorbed or
released when a specific amount of solute
dissolves in a solvent is the heat of solution.
http://www.4college.co.uk/a/O/solution.gif
http://img.sparknotes.com/figures/0/07cf18f888c9c21f4b45687743b63ac3/solnform.gif
When two liquids dissolve in each other at all
proportions they are said to be miscible (i.e.
alcohol and water); when they do not they are
called immiscible (i.e. water and oil). You can
separate immiscible liquids with a piece of
equipment called a separatory funnel (shown at
right
http://images.scran.ac.uk/RB/images/thumb/0934/09343276.jpg
Fractional
Distillation
Apparatus
knowledgerush.com
Paper Chromatography
ljcreate.com
Chromatogram Development
(KB)
Draw a line to indicate the
height of the solvent front
X the pigments to find
the center
A
B
C
Put a pencil mark to locate where the
pigment goes
Calculate the Rf = B/A and C/A
Gas chromatography (GC) is an analytical
technique for separating compounds based
primarily on their volatilities. Compounds
move through a GC column as gases. The
compounds partition between a stationary
phase, which can be either solid or liquid, and a
mobile phase (gas). The differential partitioning
into the stationary phase allows the
compounds to be separated in time and space.
http://www.cee.vt.edu/ewr/environmental/teach/smprimer/g
c/gc.html
cee.vt.edu
• Solvation: process of surrounding solute
particles with solvent particles. A solute
particle that is surrounded by solvent
molecules is said to be solvated.
• Hydration: solution process in which the
solvent is water.
see picture at right: http://robocup.mi.fuberlin.de/buch/chap6/ComparisonBatteryDateien/image002.jpg
• Dissociation is the separation of ions that occurs
when an ionic compound dissolves.
ex. NaCl (s)  Na+ (aq) + Cl- (aq)
• Ionization is the process whereby ions are
formed from solute molecules by the action of
the solvent.
ex. HCl  H+ (aq) + Cl- (aq)
• In water solutions, the H+ ion normally exists
attached to the water molecules in solution to
form the hydronium ion (H3O+)
ex. HCl (g) + H2O (l)  H3O+ (aq) + Cl- (aq)
Concentration of solutions: a measure
of the amount of solute in a given
amount of solvent or solution.
Mass percent =
mass of component in solution x 100
total mass of solution
ppm
mass of component in solution x 106
total mass of solution
number of moles of solute in one liter of
solution. Note that the total volume of the
solution is 1 liter, not that you add solute to 1
liter of solvent. The symbol for molarity is “M”
and usually referred to as an “X molar
solution.”
Molarity (M) = moles of solute
liters of solution
Dilutions of solutions
M1V1 = M2V2
= number of moles of solute
per kilogram of solvent. The symbol
for molality is “m,” and is usually
referred to as an “X molal solution.”
• molality (m) = moles of solute
kg of solvent
moles of solute
1000g of solvent
Typically when two aqueous
solutions are combined and
one of the products is
minimally soluble a PPT is
formed
http://boomeria.org/chemlectures/textass2/tableA-7.jpg
Table 1 in your textbook page 437;
Table A-12 (appendix) page 860
Na2CO3 (aq) + Ca(NO3)2 (aq) 
CaCO3 (?) + 2NaNO3 (?)
Looking at your solubility table we
see that all nitrates are soluble and
most carbonates are insoluble,
except Na, K and NH4
Thus CaCO3 (s) + 2NaNO3 (aq)
• Include only those compounds and ions that
undergo a chemical change in a reaction in an
aqueous solution.
• Spectator ions are those that do NOT take
part in a chemical reaction and are found in
solution before and after the reaction takes
place
Ionic equation:
2Na+ (aq) + CO32- (aq) + Ca2+ (aq) + 2NO3- (aq) 
CaCO3 (s) + 2Na+ (aq) + 2NO3- (aq)
Net ionic equation:
Do not include spectator ions.
Ca2+ (aq) + CO32- (aq)  CaCO3 (s)
Colligative Properties
• properties that depend on the concentration
of solute particles but not on their identity.
• Vapor pressure lowering. Boiling point is
higher and freezing point of a solution is lower
than that of a pure solvent. This is due to the
presence of nonvolatile solutes. These are
substances that have little tendency to
become a gas under existing conditions.
http://www.auset
ute.com.au/imag
es/gravpl.gif
• Freezing point depression, ∆Tf, is the difference
between the freezing points of the pure solvent
and a solution of a non-electrolyte in that
solvent, and it is directly proportional to the
molal concentration of the solution.
∆Tf = Kf m
• Kf = the molal freezing-point constant is the
freezing-point depression of the solvent in a 1molal solution of a nonvolatile, nonelectrolyte
solute. The value for this constant depends on
the solvent used. (See a reference table for
specific values)
• Boiling point elevation, ∆Tb, is the difference
between the boiling points of pure solvent
and a nonelectrolyte solution of that solvent,
and it is directly proportional to the molal
concentration of the solution.
∆Tb = Kb m
• Kb = molal boiling-point constant is the
boiling-point elevation of the solvent in a 1molal solution of a nonvolatile, nonelectrolyte
solute. The value for this constant depends on
the solvent used. (See a reference table for
specific values)
Electrolytes and colligative properties
• Keeping in mind that colligative properties
depend on the number of solute particles, not
their identity, we must know the extent to
which electrolytes dissociate.
• The higher the degree of dissociation, the
more moles of ions we have in solution, thus
increasing the net effect.
Osmosis
http://www.studentsguide.in/biol
ogy/absorption-movementimages/diagram-showingrelationship-of-osmotic-pressureturgor-pressure-wall-pressure.jpg
the diffusion of solvent
particles (water) across a
semipermeable
membrane from an area
of higher solvent
concentration to an area
of lower solvent
concentration. Osmotic
pressure is the external
pressure that must be
applied to stop osmosis.
IsaacsTEACH on Solutions, Colloids, Suspensions
https://www.youtube.com/watch?v=Ti0QroYDta8
TheChemistrySolution's Video on Henry's Law
https://www.youtube.com/watch?v=eM56JYel1aM
TheChemistrySolution's Video on Partial Pressure of
Gases and Mole Fractions
https://www.youtube.com/watch?v=agNtq38TA6o
Another Video on Henry's Law
https://www.youtube.com/watch?v=F9Fo3QJ0ApE
If these links don't seem to work directly, then cut and
paste the URL into a browser and they should work fine!