1. Different Units of Concentration
We’ve talked about molarity in the past. You need to review molarity, keeping in mind electrolyte issues
We talked about (or will talk about) molality in lab
On the next slide, you’ll see these two as well as two other units that you need to be familiar with
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2. Solution Composition 1. Molarity (M) = 2. Mass (weight) percent =
3. Mole fraction (A) =
4. Molality (m) =
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3. Worksheet Problem
1. A sample of caffeine, was dissolved in 45.0 g of chloroform to give a m solution. How many grams of caffeine were in the sample? MM(caffeine) = g/mol.
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4. Q2(a)
2. A m citric acid solution has a density of g/mL. The molar mass of citric acid is g/mol.
(a) Find the mass % of citric acid in the solution.
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5. Q2(b)
2. A m citric acid solution has a density of g/mL. The molar mass of citric acid is g/mol.
(b) What is the molar concentration of citric acid?
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6. What is solubility?
Solubility is the maximum concentration that a solute can attain in a given solvent at a given set of conditions (T & P, see sheet)
Also: The concentration of a “saturated” solution (where dissolved and undissolved solute are in dynamic equilibrium)
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7. What factors affect solubility [Part 1]?
Because of “energetics”, if interparticle forces are similar in solute and solvent, dissolution occurs.
“like dissolves like”
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8. Three Steps in the Dissolving Process (Recall “Hess’s Law”!)
1) Which processes should be:
Endothermic?
Exothermic?
2) What determines HOW exothermic Step 3 will be?
 Self-Other IM forces!!
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9. Self-self
Self-other
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10. “Self-other” IM forces (not “self-self” IM forces like last unit)
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11. Figure 11.2 a&b Dissolution Processes that are (overall) (a) Exothermic and (b) Endothermic
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12. It turns out…
Mixing is generally favorable (2nd semester will address this more [but see p in Tro])
So…(also see Table 12.2 in Tro)
An exothermic dissolution will (always) occur
A slightly endothermic dissolution will occur
But a “prohibitively” endothermic, dissolution will not occur
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13. The Energy Terms for Various Types of Solutes and Solvents
(positive)
H2
H3
(negative)
Hsoln
(= sum)
Outcome
Polar solvent, polar solute
Large
Large, negative
Small
Solution forms
Polar solvent, nonpolar solute
Large, positive
No solution forms
Nonpolar solvent, nonpolar solute
Nonpolar solvent, polar solute
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14. Tro’s “version” of prior idea
Polar/Polar and Nonpolar/Nonpolar situations
Polar/Nonpolar or Nonpolar/Polar situations
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15. Like dissolves Like Idea (Data, alcohols in water vs. hexane)
Chapter 13, Unnumbered Table, Page 577

16. Like Dissolves Like Again (Data, for gases in water)
Chapter 13, Table 13.4

17. Vitamin Solubility?
Chapter 13, Unnumbered Figure 1, Page 576

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19. Other Factors Affecting Solubility

20. Factors Affecting Solubility
Structural Effects
IM forces of solute/solvent (already discussed)
physical state of solute (see below)
Pressure Effects
Significant for Gaseous solutes only
Temperature Effects
Different for gaseous vs. solid solutes
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21. Chapter 13, Unnumbered Figure, Page 584

22. Carbonation
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23. The Solubilities of Several Gases in Water As a Function of Temperature
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24. Lake Nyos in Cameroon
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25. Chapter 13, Chemistry In The Environment Figure 1, Page 586

26. Chapter 13, Chemistry In The Environment Figure 2, Page 586

27. Chapter 13, Chemistry In The Environment Figure 3, Page 586

28. The Solubilities of Several Solids as a Function of Temperature
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