1. Copyright © Houghton Mifflin Company. All rights reserved.11–1 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

2. Copyright © Houghton Mifflin Company. All rights reserved.11–2 Solution Composition 1.Molarity (M) = 2.Mass (weight) percent = 3.Mole fraction (  A ) = 4.Molality (m) =

3. Copyright © Houghton Mifflin Company. All rights reserved.11–3 Worksheet Problem 1. A sample of caffeine, was dissolved in 45.0 g of chloroform to give a 0.0946 m solution. How many grams of caffeine were in the sample? MM(caffeine) = 194.1 g/mol.

4. Copyright © Houghton Mifflin Company. All rights reserved.11–4 Q2(a) 2. A 0.688 m citric acid solution has a density of 1.049 g/mL. The molar mass of citric acid is 192.12 g/mol. (a) Find the mass % of citric acid in the solution.

5. Copyright © Houghton Mifflin Company. All rights reserved.11–5 Q2(b) 2. A 0.688 m citric acid solution has a density of 1.049 g/mL. The molar mass of citric acid is 192.12 g/mol. (b) What is the molar concentration of citric acid?

6. Copyright © Houghton Mifflin Company. All rights reserved.11–6 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)

7. What factors affect solubility [Part 1]? Because of “energetics”, if interparticle forces are similar in solute and solvent, dissolution occurs. –“like dissolves like” Copyright © Houghton Mifflin Company. All rights reserved.11–7

8. Copyright © Houghton Mifflin Company. All rights reserved.11–8 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!!

9. Copyright © Houghton Mifflin Company. All rights reserved.11–9 Figure 11.2 a&b Dissolution Processes that are (overall) (a) Exothermic and (b) Endothermic

10. It turns out… Mixing is generally favorable (2 nd semester will address this more [but see p. 515-516 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 Copyright © Houghton Mifflin Company. All rights reserved.11–10

11. Copyright © Houghton Mifflin Company. All rights reserved.11–11 The Energy Terms for Various Types of Solutes and Solvents  H 1 (positive)  H 2 (positive)  H 3 (negative)  H soln (= sum) Outcome Polar solvent, polar solute Large Large, negative SmallSolution forms Polar solvent, nonpolar solute SmallLargeSmallLarge, positive No solution forms Nonpolar solvent, nonpolar solute Small Solution forms Nonpolar solvent, polar solute LargeSmall Large, positive No solution forms

12. Other Factors Affecting Solubility

13. Copyright © Houghton Mifflin Company. All rights reserved.11–13 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

14. Copyright © Houghton Mifflin Company. All rights reserved.11–14 A Gaseous Solute

15. Copyright © Houghton Mifflin Company. All rights reserved.11–15 Carbonation

16. Copyright © Houghton Mifflin Company. All rights reserved.11–16 The Solubilities of Several Gases in Water As a Function of Temperature

17. Copyright © Houghton Mifflin Company. All rights reserved.11–17 Lake Nyos in Cameroon

18. Copyright © Houghton Mifflin Company. All rights reserved.11–18 The Solubilities of Several Solids as a Function of Temperature