Solutions

1
Solutions

• Solution Homogeneous mixture, a mixture in
  which the components are uniformly intermingled.
• Solvent Substance present in the largest
  amount.
• Solute Substance present in the smallest
  amount.
• Aqueous Solutions Solutions with water as the
  solvent.

2
Solubility

• What happens when you dissolve NaCl in water?
• When an ionic substance dissolves in water, it
  breaks up into individual cations and anions
  where are dispersed in water. There are strong
  water ions interactions when the solid dissolves.

3
Solubility

• Water also dissolves many nonionic substances.
  Sugar and ethanol dissolves in water. Both
  contain polar O-H groups. These H-Bond to water
  molecules.

4
Solubility

• Oil and water do not mix. Oil is nonpolar and
  water is polar. Oil floats on the surface of
  water because its density is less than that of
  water.

5
Solution CompositionAn Introduction

• Saturated Solution A solution that contains as
  much solute as will dissolve at a given
  temperature.
• Unsaturated Solution A solution that has not
  reached the limit of solute that will dissolve.
• Concentrated Solution A solution that has a
  relatively large amount of solute dissolved.
• Dilute Solution A solution that has a
  relatively small amount of solute dissolved.

6
Making supersaturated solns

• Make sat. soln
• Cool it slowly and carefully
• Lower temperatures reduced the rate of
  crystallization
• Once disturbed (energy in), causes
  crystallization to occur ? excess crystallized
  out of soln
• Exothermic
• Heat packs of sodium acetate (can reach 50C!)
• http//www.npr.org/programs/wesun/features/2001/de
  c/heatpack/011229.heatpack.html
• Lets talk about enthalpy of crystallization in
  lab 2

7

• Drinks carbonated under high pressure
• Above 90 atmospheres
• So under CO2 atmosphere
• Once bottle opened, partial pressure of gas above
  soda plummets
• CO2 solubility decreases drastically
• Gas bubbles out of solution

8
The bends

• Deeper diving has higher pressures
• Must use breathing tank
• If it contains N2 then higher pressure forces N2
  to dissolve in higher amounts in blood
• If ascension too fast, lower pressure causes N2
  to start bubbling out of blood too quickly ?
  rupturing of arteries ? excruciatingly painful
  death
• Must be rushed to hyperbaric chamber

9
Antifreeze

• Lowers freezing pt
• Increases boiling pt
• Reduces risk of radiator boiling over
• Appreciated during the summer months in the
  desert
• Propylene glycol replacing ethylene glycol

10
Colloids

• From Greek glue
• Btwn suspensions (fine sand in water, mixed up)
  solns
• 1) Have very high molar masses
• 2) Have large sizes starch, for ex.
• 3) Tyndall effect ? scatter a beam of light
• 4) Do not settle out like suspensions
• 5) Not the same as hemorrhoids

11
Emulsions

• Colloidal dispersions of one liquid in another
• Mayo, milk
• Liquids of different polarities are immiscible
• Need emulsifying agent
• Such as soap (one polar end, one non) proteins
  ()
• In food items ? soy lecithin
• In the world of cleaning ? surfacants (soaps,
  etc.)

12
Surfacants

• NaOH animal or veggie fat ? Na fatty acid-
• The fatty acid has a long non-polar tail and a
  very polar carboxylate group
• Can be used to take away (clean) non-polar
  entities like oil, dirt
• Surfacants (soap) used in cleaning detergent

13
Detergents

• Lowers surface tension of water (disrupts
  H-bonding)
• Enhances action of detergent
• Lets watch the following video
• http//www.ilpi.com/genchem/demo/tension/demo
• Sodium lauryl sulfate (soaps, shampoos)

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Solution CompositionMass Percent

• Mass Percent or weight percent describes a
  solutions composition.
• The equation for Mass Percent is given below.
• Mass Percent mass of
  solute x 100
• 
  mass of solution
• Mass Percent grams of solute
  x 100
• grams of solute
  grams of solvent

15
Solution CompositionMass Percent

• Example
• A 135 g sample is evaporated to dryness, leaving
  4.73 g of solid residue. Calculate the mass
  percent of solute present.

16
Solution Composition Molarity

• Molarity Number of moles of solute per volume
  of solution in liters.
• Example A solution that is 1.0 M contains 1.0
  mol per 1 L of solution.
• The equation for Molarity is given below.
• M Molarity
  moles of solute mol
• 
  liters of solution L

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Solution Composition Molarity

• Standard Solution Solution whose concentration
  is accurately known.
• Stock Solution Solutions that are routinely
  used and purchased or prepared in concentrated
  form.
• Dilution The process of adding more solvent to
  a solution. Only water is added in a dilution.