Liquid Mixtures

1
Liquid Mixtures

• Chapter 10

2
Goals

• Understand the importance and properties of
  solutions
• Express concentration various ways
• Understand properties of emulsions, suspensions,
  and colloids
• Understand osmosis and dialysis

3
General Properties of Solutions

• Solute - what is dissolved in the solvent
• Solvent - what dissolves the solute
• Doesnt have to be water. Alcohol, ether etc.
• Variable concentration
• Clear - may have color (jello)
• Homogeneous
• Dont settle
• Can be separated by physical means
• Pass through filter paper

4
Factors Affecting Solubility

• Temperature
• High temp solids more soluble, gases less.
• Pressure
• Only affects gases. High p more soluble.
• Surface Area
• Only affects rate of dissolving.
• Stirring
• Only affects rate of dissolving
• Nature of Solvent
• Like dissolves like.

5
Importance of Solutions

• Drugs must be in solution to be absorbed into the
  GI tract.
• Liquids (syrups, elixirs) are more rapidly
  absorbed than powders (tablets).

6
Strength of Solutions

• Unsaturated - amount of solute less than maximum
  solution can hold (dilute)
• One package, two hands
• Saturated - amount of solute is the maximum
  solution can hold (concentrated)
• Two packages, two hands
• Supersaturated - holds more than maximum
• Many packages, two hands
• Heat solution with lots of solute then cool
  slowly.

7
Expressing Concentration

• Percent solutions (w/v)
• Grams solute/volume solvent 100
• Parts per million (ppm)
• Same as mg/L
• Ratio Solutions
• First number is amout solute, second is solvent
• 1100 means 1g solute in 100g solvent.
• Molar Solutions
• Moles solute/ volume solvent in L

8
Special Properties of Solutions

• Solutes increase boiling point and decrease
  freezing point compared to pure solvent.
• Solutes decrease surface tension
• Detergents, bile, lung function

9
Osmotic Pressure

• Diffusion - molecules move from areas of high
  concentration to areas of low concentration.
• Osmosis - when diffusion happens across a
  membrane (cells, dialysis) Reverse Osmosis?
• Osmotic Pressure - amount of pressure we must
  apply to stop diffusion.
• Osmolarity molarity particles per molecule
• Or p MRT
• Body fluids about 300 miliosmol
• Plasma proteins (albumin) regulate
• osmotic pressure in blood

10
Solutions for diffusion - or not

• Hypotonic solution - the solution you are adding
  is less concentrated than what youre putting it
  into.
• Hypertonic solution - the solution you are adding
  is more concentrated than what youre putting it
  into
• How do these affect blood cells?
• Isotonic solutions - two solutions with same
  concentration
• Used after surgery, to prevent dehydration.
• Dont effect blood cells.

11
Suspensions

• Many medications are suspensions
• Milk of magnesia, antibiotics, nebulized drugs
  suspended in air
• Properties
• Dont dissolve
• Heterogeneous
• Not clear
• Settle
• Dont pass through filter paper or membranes

12
Colloids

• Like suspensions, they dont dissolve or pass
  through most membranes.
• Unlike suspensions, they are smaller so they pass
  through filter paper and some membranes.
• Small size gives lots of surface area so rapidly
  adsorbed.
• Charcoal used for patients who ingested poisons
• All same particles have same electric charge -
  repel, keeping them suspended.

13
Colloids, continued

• Tyndall effect - laser passes straight through
  solutions, scatters in colloids and suspensions.
• Brownian Motion - molecules are always moving by
  haphazard collisions. This keeps molecules from
• settling.
• Watch dust in a sun beam.

14
Subclasses of Colloids

• Gels - hydrophillic, semisolid, dont flow
• Sols - hydrophobic, pour easily
• Aerosols colloidal dispersions in air

15
Hemodialysis

• Dialysis separates colloids from solutes by
  semipermeable membrane.
• Colloids are RBCs and proteins, solutes are
  sodium chloride,other inorganic salts, and
  metabolic waste products.

16
Emulsions

• Two immiscible compounds mixed
• Temporary if they settle on standing
• Oil and water
• Permanent if they dont
• Mayonnaise (oil and water with an emusifying
  agent - egg white)
• Neither are clear.