Solutions and Solubility Chapter 8

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Solutions and SolubilityChapter 8
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What is a solution?

• homogeneous mixture uniform throughout
• solvent is present in
• larger amount
• solute refers to
• what is dissolved
• a given solution can be made up of different
  amounts of solute and solvent
• eg 0.10 mol/L NaCl(aq) 0.50 mol/L NaCl(aq)

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Some types of Solutions

• solute solvent examples
• gas gas air, natural gas
• gas liquid O2(aq)fish breathe this
  CO2(aq) in carbonated drinks
• liquid gas water vapour in air
• liquid liquid ethanol(aq)vodka
• antifreeze(aq)
• liquid solid amalgamHg(Au)
• solid liquid tea(aq)
• solid solid alloyscoins

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Be careful with antifreeze . . .

• Aqueous solutions of ethylene glycol,
  CH2(OH)CH2(OH)(aq), aka
• antifreeze, are coloured
• fluorescent green. Why?
• Easy identification of a spill.
• Antifreeze has a sweet taste and can be
  attractive to pets.
• As little as one teaspoon of
• antifreeze can be deadly to a cat
• similarly for dogs.

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Composition of dry air

• 78 N2
• 21 O2
• 0.9 Ar
• CO2 0.03
• What is the solvent in air?
• N2

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What governs solubility?

• Like dissolves
• like.
• Polar dissolves
• polar i.e.
• Many ionic salts are water soluble due to
• ion-dipole attractions. For non-ionic solutes, in
  water, dont forget possibility of
• hydrogen bonding.
• Non-polar dissolves
• non-polar.

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• Important definition
• Miscible refers to liquids that are mutually
  soluble in any proportion.
• eg. Ethanol and water are soluble in any
  combination.

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Water Solubility of Some Ionic Solutes as a
Function of Temperature
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Unsaturated, Saturated, Supersaturated Solutions

• A saturated solution is formed when no more
  solute will dissolve in a given amount of
  solvent, at a certain temperature.
• What will happen if additional solute is added to
  a saturated solution?
• The excess solute will not dissolve. It will
  usually sink.

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• An unsaturated solution can dissolve more solute
  at a given temperature.
• What will you observe if additional solute is
  added to an unsaturated solution?
• It will dissolve.
• A supersaturated solution contains more dissolved
  solute than it is allowed to have dissolved at
  a given temperature.
• Lets do the lab . . .

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Homework

• Brief, point-form answers to
• p 357 Learning Check 1 to 6
• RQs 1 to 9, 13, 15
• Lets look at an interesting problem . . .

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• In 1989, the oil tanker Exxon Valdez struck a
  reef in Prince William sound, Alaska. The
  accident released 40 million litres of crude oil,
  eventually covering 26,000 km2 of water.
• What was the average depth of the oil slick?
• What additional information is required to solve
  this problem?
• Assume average density of crude oil to be 0.86
  g/mL 1 L (10 cm)3

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• Exxon Valdez Oil Spill Calc. average thickness
  of oil slick
• Voil 40E06 L
• area 26E03 km2
• oil slick as shape of a
• rectangular prism
• Volume
• area thickness
• What do we need to do with the units of area and
  volume, above?

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• Get consistent units for volume and area
• Voil 40E06 L
• ? /1000Lm-3
• 40E03 m3
• A 26,000 km2 (1000 m)2/km2
• 2.6E10 m2
• Volume A thickness
• thickness V/A
• 40E03 m3/ 2.6E10 m2
• 1.5E-06 m or 1.5E-03 mm is
• thickness of oil slick.