1. SOLUTIONS
Chemistry 21A Dr. Dragan Marinkovic

2. SOLUTIONS supersaturated solution
A solution is a homogeneous mixture of a solute and a solvent. Solutions can be formed in any state of matter; that is they may be solid, liquid, or gas.
A solution is prepared by dissolving a solute into the solvent.
Solute is either the smaller component of a mixture or, when liquid solutions are considered, the gaseous or solid substance added to the solution.
Solutions could be composed of either complete molecules (atoms) - molecular solution, or ions - ionic solution. The latter usually is referred to aqueous solutions of salts. Fluids that mix or dissolve in each other in all proportions are call miscible fluids, lacking that property fluids are called immiscible. So gases are always miscible
miscible immiscible
soluble insoluble
saturated unsaturated solution
dissolve precipitate (crystallize)
supersaturated
solution
Chemistry 21A Dr. Dragan Marinkovic

3. SOLUTIONS NaCl(s) <==> Na+(aq) + Cl-(aq)
SOLUBILITY
The maximum amount of
solute that can be dissolved
in a specific amount of
solvent at specific
temperature and pressure.
NaCl(s) <==> Na+(aq) + Cl-(aq)
If there is more solute dissolved than
saturation allows, the solution is said to
be supersaturated. supersaturated solution
Chemistry 21A Dr. Dragan Marinkovic

4. SOLUTIONS
Solubility in water with temperature under 1 atm pressure, units of solubility in g/100g H2O.
Substance Formula 0°C 10°C 20°C 30°C °C
Helium He
Hydrogen chloride HCl
Fructose C6H12O
Ammonia NH
(Unit:mL/mL)
Ammonium chloride NH4Cl
Calcite CaCO
Magnesium carbonate MgCO
Magnesium chloride MgCl
Oxygen O
Chemistry 21A Dr. Dragan Marinkovic

5. solute solubility (g solute in 100 g water)
SOLUTIONS
solute solubility (g solute in 100 g water)
solubility term
less than 0.1
insoluble
slightly soluble
1 - 10
soluble
greater than 10
very soluble
Chemistry 21A Dr. Dragan Marinkovic

6. SOLUTIONS
Chemistry 21A Dr. Dragan Marinkovic

7. SOLUTIONS Polar solvents will dissolve polar
‘LIKE DISSOLVES LIKE”
Polar solvents will dissolve polar
or ionic solutes and nonpolar
solvents will dissolve nonpolar
or nonionic solutes.
Chemistry 21A Dr. Dragan Marinkovic

8. SOLUTIONS
Chemistry 21A Dr. Dragan Marinkovic

9. SOLUTIONS Heat of Solution
The process of dissolving is a process which involves the breaking and making of bonds, and that involves energy.
Dissolution overall can be either endothermic or exothermic, depending on whether more energy was used to break the bonds,
or more energy was released when new bonds were formed.
The breaking of bonds requires or absorbs energy.
Using energy like that is called endothermic.
If more energy is used than is released, the process is endothermic.
SOLUTE + SOLVENT + HEAT SOLUTION
The formation of bonds releases energy. That is called exothermic.
If more energy is released in making bonds than is used
in breaking bonds, the process is exothermic.
SOLUTE + SOLVENT SOLUTION + HEAT
Chemistry 21A Dr. Dragan Marinkovic

10. SOLUTIONS
CONCENTRATION
Concentration -- amount of a solute present in a solution per standard amount of solvent
Weight/Weight Percent (w/w%):
This unit of concentration is often used for concentrated solutions, typically acids and bases.
If you were to look on a bottle of a concentrated
acid or base solution the concentration expressed
as a weigh/weight percent.
RED DYE
Molarity (M):
This unit of concentration
Relates the moles of solute
per liter of solution.
w/v%
milliliters of solution
solute volume
v/v%
solution volume
Chemistry 21A Dr. Dragan Marinkovic

11. SOLUTIONS
SOLUTION PREPARATION
Solutions are prepared by mixing proper amounts of solute and solvent or by diluting
a concentrated solution by a solvent to produce
a solution of lower concentration.
a single ring graduation mark
mass m
density = = = d
volume V
w/v%
m = d x V
milliliters of solution
solute volume
v/v%
solution volume
Chemistry 21A Dr. Dragan Marinkovic

12. (Mconc) (Vconc) = (Mdil) (Vdil)
SOLUTIONS
SOLUTION PREPARATION
Dilution is preparing a solution of lower concentration by
diluting a solution of higher concentration (“stock solution”).
There is an element of simplicity in calculations. The number of moles of solute in the concentrated solution is equal to the number of moles in the dilute solution. You have simply increased the amount of solvent in the solution.
molescon = molesdil
(Mconc) (Vconc) = (Mdil) (Vdil)
This equation is true for any solution
concentration based on volume.
Chemistry 21A Dr. Dragan Marinkovic

13. NaCl(aq) Na+(aq) + Cl -(aq)
SOLUTIONS
SOLUTION PROPERTIES
Electrolyte is chemical compound that ionizes when dissolved in water to produce an electrically conductive medium.
WATER
SUGAR SOLUTION
NaCl SOLUTION
Nonelectrolyte is chemical compound that does not ionize when dissolved in water and does not produce an electrically conductive medium.
NaCl(aq) Na+(aq) Cl -(aq)
Chemistry 21A Dr. Dragan Marinkovic

14. SOLUTIONS Vapor pressure depression Boiling point elevation
SOLUTION PROPERTIES
Vapor pressure depression
Boiling point elevation
The vapor pressure of a solution is
lower than that of the pure solvent
Freezing point depression
Chemistry 21A Dr. Dragan Marinkovic

15. SOLUTIONS
SOLUTION PROPERTIES
Kb = boiling constant
characteristic for the solvent used
Colligative property of a solution depends only on the ratio of the number of particles of solute and solvent in the solution, not the identity of the solute.
Kf = freezing constant
characteristic for the solvent used
K = constant characteristic
for the solvent used
∆t = nKm
∆t = boiling or
freezing point difference
The factor n accounts for the number of individual particles (typically ions) formed by a compound in solution. Examples:
n = 1 for sugar in water
n = 2 for sodium chloride in water, due to the full dissociation of NaCl into Na+ and Cl-
n = 3 for calcium chloride in water, due to dissociation of CaCl2 into Ca2+ and 2Cl- ≈
= m
= M
molality
kg solvent
For dilute
Solutions.
Chemistry 21A Dr. Dragan Marinkovic

16. SOLUTIONS SOLUTION PROPERTIES ∆t = nKm
Chemistry 21A Dr. Dragan Marinkovic

17. Osmosis transfer of a liquid
SOLUTIONS
SOLUTION PROPERTIES
Osmosis
In osmosis,
water (solvent) flows from the lower
solute concentration into the higher solute concentration.
The level of the solution with the higher concentration rises.
The concentrations
of the two solutions become equal with time.
Osmosis transfer of a liquid
solvent through a semipermeable membrane that does not allow dissolved solids (solutes) to pass. Osmosis refers only to transfer of solvent; transfer of solute is called dialysis. In either case the direction of transfer is from the area of higher concentration of the material transferred to the area of lower concentration. This spontaneous migration of a material from a region of higher concentration to a region of lower concentration is called diffusion.
Chemistry 21A Dr. Dragan Marinkovic

18. SOLUTIONS
SOLUTION PROPERTIES
molality
universal gas constant
Setup for Measuring the
Osmotic Pressure of a Solution
π = nMRT
temperature (K)
Osmotic pressure is the hydrostatic pressure produced by a difference in concentration between solutions on
the two sides of a surface such as a semipermeable membrane.
The factor n accounts for the number of individual particles
Chemistry 21A Dr. Dragan Marinkovic

19. Red blood cells have cell walls that are semipermeable membranes.
SOLUTIONS
SOLUTION PROPERTIES
Red blood cells have cell walls that are semipermeable membranes.
Maintain an osmotic pressure that cannot change or damage occurs.
Must maintain an equal flow of water between the red blood cell and its surrounding environment.
An isotonic solution
exerts the same osmotic pressure as red blood cells.
is known as a “physiological solution”.
of 5.0% glucose or 0.90% NaCl is used medically because each has a solute concentration equal to the osmotic pressure equal to red blood cells.
Chemistry 21A Dr. Dragan Marinkovic

20. SOLUTIONS SOLUTION PROPERTIES In dialysis,
solvent and small solute particles pass through an artificial membrane.
Large particles are retained inside.
Waste particles such as urea from blood are removed using hemodialysis (artificial kidney).
This graphic illustrates the dialysis process. First, the concentrated protein solution is placed in dialysis bag with small holes which allow water and salt to pass out of the bag while protein is retained. Next the dialysis bag is placed in a large volume of buffer and stirred for many hours (16 to 24 hours), which allows the solution inside the bag to equilibrate with the solution outside the bag with respect to salt concentration. When this process of equilibration is repeated several times (replacing the external solution with low salt solution each time), the protein solution in the bag will reach a low salt concentration:
Chemistry 21A Dr. Dragan Marinkovic

21. SOLUTIONS SOLUTION PROPERTIES
In hemodialysis, the patient's blood is pumped through the blood compartment of a dialyzer, exposing it to a semipermeable membrane. The cleansed blood is then returned via the circuit back to the body. Ultrafiltration occurs by increasing the hydrostatic pressure across the dialyzer membrane.
Chemistry 21A Dr. Dragan Marinkovic