Todays goals

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Todays goals

• Solubility

2
Admin stuff

• OWLs next OWLs due Mon, Thur
• Reading Current Ch. 5.1-5.7
• Next test Nov. 20 (Tue, 6-730 PM)
• I need to hear about conflicts by the end of
  class TODAY

3
PRS - Thanksgiving

• I am traveling more than 250 miles for
  Thanksgiving
• Yes
• No

4
PRS on Nov. 22 lecture

• If I were to give an optional lecture on molarity
  and solution concentrations on Wed, Nov. 22,
  would you attend?
• Yes
• No

5
Solubility
6
Solution chemistry

• A solution is a homogenous mixture of two or more
  substances.
• The substance present in the largest amount is
  the solvent.
• The other components are called solutes.
• Ionic compounds break apart into their
  constituent ions (5.2 on CD)

7
What are the atoms doing when a compound
dissolves?
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Water

• Although water on the whole is neutral, the
  oxygen atom has a partial negative charge while
  the hydrogen atom has a partial positive charge.
• This Coulombic interaction is what makes it
  favorable for ionic materials to dissolve.

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What are common solutes?

• Many ionic compounds dissolve in water
• (charged solute / polar solvent)
• Organic molecules dissolve in organic solvents
• (neutral solute / non-polar solvent)
• Rule of thumb Like dissolves like

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What are common solvents?

• Water!!
• Small organic molecules acetone, benzene,
  toluene, methanol, ethanol, etc.
• Even gases can behave as solvents at sufficiently
  high pressures (CO2)

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Ionic compounds dissolved in water

• Ionic compounds break apart into their
  constituent ions (5.2 on CD)
• Compounds whose solutions conduct electricity are
  called electrolytes (7.7 description - step
  problem)
• Strong electrolytes, weak electrolytes,
  non-electrolytes (5.3, part 2)

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Solubility demo

• Cobalt chloride
• Pure water, tap water
• Salt water, sugar water

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• Soluble and homogenous
• vs
• Insoluble and heterogenerous

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Ca(OH)2, Ba(OH)2
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Solubility
Which is most important in determining whether or
not an ion is likely to be soluble? (a) ion size
(b) sign of charge
(c) period of central atom (d)
magnitude of ionic charge (e) bonding
orbitals
17
Are these compounds soluble?

• KBr
• BaCl2
• ZnO
• (NH4)2CO3
• AgCl

soluble (potassium) soluble (chloride) insoluble
(oxide) soluble (carbonate exception) insoluble
(chloride exception)
How many of these compounds are soluble? (a)
1 (b) 2 (c) 3 (d) 4 (e) 5
18
Precipitation reactions

• Does it affect the solubility of a chemical if
  the two positive and negative ions of an ionic
  solid are added together or separately?

NO!

• What happens when two different soluble ionic
  compounds are mixed?
• If any combination of ionic species is
  insoluble, a precipitate will form.
• If all combinations of ions are soluble, nothing
  will happen