PS 101

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PS 101

• Kim Cohn
• Email address
• Kcohn_at_academic.csubak.edu

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Comments- Chromatography

• If you used the same inks what could have been
  changed to get a better separation?
• Solvent (mobile phase) mixtures.
• Paper (stationary phase).
• Lengthen stationary phase.

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Comments- Chromatography

• Some chromatography
• uses gas for the mobile phase,
• forces the liquid or gas through the stationary
  phase, or
• The purity of almost all drugs and many other
  substances is tested by chromatography.

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Comments- Chromatography

• DNA testing is done by chromatography.
• Good drug testing is done by chromatography.
• uses different stationary phase such as clay.

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Molecular Mixing

• Like dissolves like.
• Remember that when the two atoms are different
  one of the atoms may have more of the electron
  density than another.
• For example, HF.
• H?- F?- The symbol ? means slightly positive.

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Molecular Mixing 2

• The bond in H?- F?- is called a polar bond.
• H2O also has polar bonds.
• Polar solvents will usually dissolve ionic
  compounds.
• H2O will dissolve NaCl.
• H2O will not dissolve olive oil or grease.

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Molecular Mixing 3

• H2O has polar bonds.
• Polar solvents will usually dissolve ionic
  compounds.
• Polar solvents will usually dissolve other
  compounds that are polar, such as alcohol.

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Molecular Mixing 4

• The bond in C-C is a non-polar bond.
• Gasoline is made of many different compounds all
  of which have non-polar bonds.
• Non-polar solvents will usually dissolve
  Non-polar compounds.
• Gasoline will not dissolve NaCl.
• Gasoline will dissolve olive oil or grease.

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Solutions

• Add sugar to water to form a homogeneous mixture
  called a solution.
• The sugar is the solute.
• Water is the solvent.
• Can have many different types of solutions.

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Solutions 2
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Solutions 3

• Concentrated No real meaning.
• Dilute no real meaning.
• Saturated The solvent holds as much solute as
  possible.
• Unsaturated.
• Insoluble solute does not dissolve.

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Solutions 4
Amount of solute ?
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Solutions 5

• 12 pencils is a pencils?
• 144 pencils is a of pencils?
• 500 sheets of paper is a ?
• 6.02 x 1023 of anything is a
• Mole

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Solutions 6
Not this type of Mole
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Or this type of Mole
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Solutions 7

• 6.02 x 1023 is a mole -602,000,000,000,000,000,000
  
• If you counted paper at the rate of one sheet per
  second it would take you 19,089,294,774,226,281
  years to count a mole of paper.
• It is a big number because atoms are small.

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Solutions 8

• A mole of sugar weighs about one half pound but
  contains how many molecules of sugar?
• 602,000,000,000,000,000,000
• 6.02 x 1023 molecules.
• More about moles later.

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Solutions 9
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Question

• How many moles of sugar are there in 3.0 liters
  of a 0.5 M solution of sugar?
• 1.5
• 3
• 6
• 0.166
• None of the above

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Question

• If you need 1.5 moles of sugar how many liters of
  solution do you need to use if the solution is
  0.5 M?
• 1.5
• 3
• 6
• 0.166
• None of the above

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Solubility

• Remember like dissolves like.
• The formula for ethanol, the alcohol we drink, is
  C2H5OH.
• The formula for water is HOH.
• Ethanol and water are soluble in each other.

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Cultural Interest

• The concentration units of liquor, wine and beer
  is proof.
• Proof is the concentration/2.
• 100 proof alcohol is 50 ethanol.
• 1 glass beer 1 glass wine 1 mixed drink.
• Legally drunk is 2 drinks/hour for a 150 pound
  man.
• Or about 1.5 drinks/hour for the same weight of
  woman.

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Solubility 2

• Sugar contains many OH bonds.
• It will also dissolve in water.
• About 200 g of sugar will dissolve in 100 mLs of
  water.
• Oxygen, a gas, contains no OH bonds and is not
  very soluble in water.
• About 0.004 g of O2 will dissolve in water.

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Solubility 3

• The solubility of a solid will usually go up as
  the temperature goes up.
• The solubility of a gas will always go down as
  the temperature goes up.
• The solubility of a gas will always go up as the
  pressure goes up.
• What happens when you open a can of soda?

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Soap
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Soap 2
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Hard Water

• Contains the dissolved salts of iron (Fe2),
  calcium (Ca2) or magnesium (Mg2).
• These ions form a precipitate with soap.
• Squeaky clean??
• I dont think so.

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Hard Water 2

• Can add Na2CO3, sodium carbonate or washing soda,
  to hard water.
• These ions form a precipitate with the Ca2 ions.
• Can call the Culligan man and replace the Ca2
  ions with Na ions.
• Watch out if you have high blood pressure.

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Capillary action
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Capillary action 2
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Capillary Action 3

• It takes more energy to break through the surface
  of water than move through the bulk of the
  liquid.
• This is why bugs can skate along the surface of
  the water.
• Or, if you are careful, you can float a paper
  clip on water.

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Capillary Action 4

• You can reduce the surface tension by adding soap
  to water.
• Because of surface tension water will creep up
  small tubes.
• Surface tension is important in bringing water up
  in plants.
• You can drown a duck by reducing the surface
  tension of the water a duck swims in.