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Solutions• Solutions are homogeneous mixtures of two or
more pure substances.• In a solution, the solute is dispersed uniformly
throughout the solvent.
Solutions
Have small particles (ions or molecules)
Are transparent
Do not separate
Cannot be filtered
Do not scatter light.
Types of Solutions
• Saturated:Solvent holds as much solute as is possible at that
temperature.• Unsaturated:
Less than the maximum amount of solute for that temperature is dissolved in the solvent.
• Supersaturated:Solvent holds more solute than is normally possible at
that temperature.
Mass Percentage
Mass % of A =mass of A in solutiontotal mass of solution 100100
Percent (by mass) =g solute
g solutionx 100
g solute
g solute + g solvent
x 100=
• % (w/w) =
• % (w/v) =
• % (v/v) =
% Concentration
100xsolutionmasssolutemass
100xsolutionvolumesolutemass
100xsolutionvolumesolutevolume
Parts per Million andParts per Billion
ppm = mass of A in solutiontotal mass of solution 101066
Parts per Million (ppm) ((g/g, mg/L)g/g, mg/L)
Parts per Billion (ppb) (ng/g, (ng/g, g/L)g/L)
ppb =ppb = mass of A in solutiontotal mass of solution
101099
The units ppm or ppb are used to express trace concentrations.
These are weigh or volume based, rather than mole based.
The units ppm or ppb are used to express trace concentrations.
These are weigh or volume based, rather than mole based.
Colloids
Have medium size particles
Cannot be filtered
Separated with semipermeable
membranes
Scatter light (Tyndall effect)
Colloids in Biological Systems
Some molecules have a polar, hydrophilic (water-loving) end and a nonpolar, hydrophobic (water-hating) end.
Colloids in Biological Systems• Sodium stearate is one example of
such a molecule.
• These molecules can aid in the emulsification of fats and oils in aqueous solutions.
Osmosis and Osmotic Pressure
►Osmosis: The passage of solvent through a semipermeable membrane separating two solutions of different concentration.
►Osmotic pressure: The amount of external pressure applied to the more concentrated solution to halt the passage of solvent molecules across a semipermeable membrane.
Osmotic Pressure
Produced by the number of solute particles
dissolved in a solution
Equal to the pressure that would prevent
the flow of additional water into the more
concentrated solution
Increases as the number of dissolved
particles increase.
Osmotic Pressure of the Blood
Cell walls are semipermeable membranes
The osmotic pressure of blood cells
cannot change or damage occurs.
The flow of water between a red blood
cell and its surrounding environment
must be equal.
24
Isotonic solutions
• Exert the same osmotic pressure as red blood cells.
• Medically 5% glucose and 0.9% NaCl are used their solute concentrations provide an osmotic pressure equal to that of red blood cells
H2O
Hypotonic Solutions
Lower osmotic pressure than red blood cells
Lower concentration of particles than RBCs
In a hypotonic solution, water flows into the
RBC
The RBC undergoes hemolysis; it swells and
may burst.
H2O
Hypertonic Solutions
Has higher osmotic pressure than RBCHas a higher particle concentration In hypertonic solutions, water flows out
of the RBCThe RBC shrinks in size (crenation)
H2O
Dialysis
Occurs when solvent and small solute
particles pass through a semipermeable
membrane
Large particles retained inside
Hemodialysis is used medically (artificial
kidney) to remove waste particles such as
urea from blood.