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 Copyright © Houghton Mifflin Company. All rights reserved.

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

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. Copyright © Houghton Mifflin Company. All rights reserved.

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. Copyright © Houghton Mifflin Company. All rights reserved.

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? Copyright © Houghton Mifflin Company. All rights reserved.

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) Copyright © Houghton Mifflin Company. All rights reserved.

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.

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!! Copyright © Houghton Mifflin Company. All rights reserved.

Self-self Self-other Copyright © Houghton Mifflin Company. All rights reserved.

“Self-other” IM forces (not “self-self” IM forces like last unit) Copyright © Houghton Mifflin Company. All rights reserved.

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

It turns out… Mixing is generally favorable (2nd 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.

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 Copyright © Houghton Mifflin Company. All rights reserved.

Tro’s “version” of prior idea Polar/Polar and Nonpolar/Nonpolar situations Polar/Nonpolar or Nonpolar/Polar situations Copyright © Houghton Mifflin Company. All rights reserved.

Like dissolves Like Idea (Data, alcohols in water vs. hexane) Chapter 13, Unnumbered Table, Page 577

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

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

Copyright © Houghton Mifflin Company. All rights reserved.

Other Factors Affecting Solubility

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 Copyright © Houghton Mifflin Company. All rights reserved.

Chapter 13, Unnumbered Figure, Page 584

Carbonation Copyright © Houghton Mifflin Company. All rights reserved.

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

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

Chapter 13, Chemistry In The Environment Figure 1, Page 586

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

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

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