Chapter 10 Solutions

1. Chapter 10Solutions

2. Concentration Units General Vocabulary: Solution – homogeneous mixture of solute and solvent Solute – the substance being dissolved Solvent – the substance doing the dissolving Electrolyte – a substance that conducts electricity when in solution - ionic Nonelectrolyte – a substance that does NOT conduct electricity when in solution - molecular

3. Concentration Units • Molarity – (M) moles of solute per liter of solution • Molarity = moles of solute/liters of solution Example: What is the molarity of a solution made by dissolving 12.5g of oxalic acid (H2C2O4) in 456mL of solution?

5. Dilution of Solutions M1V1 = M2V2

6. Example 10.1

7. Mass Percent • Percent by mass = (mass solute/mass solution) * 100

8. Molality • the number of moles of solute per kilogram of solvent Molality (m) = moles of solute/kilograms of solvent

9. Example

10. Conversions Between Concentration Units Start with a fixed amount of solution or solvent, see right column

11. Example:

12. Principles of Solubility • Factors that determine the extent to which a solute dissolves in a particular solvent: 1. The nature of solvent and solute particles and the interaction between them 2. The temperature at which the solution forms 3. The pressure, in cases of gaseous solutes

13. Solute-Solvent Interactions • “Like dissolves like” = see table in notes • Polar solutes dissolve in polar solvents • Nonpolar solutes dissolve in nonpolar solvents • Nonpolar substances have poor affinity for water • Petroleum • Hydrocarbons (pentane, C5H12) • Polar substances dissolve easily in water • Alcohols, CH3OH • Solubility of alcohols decreases as the molar mass of the alcohol increases

14. Solubility and Intermolecular Forces

15. Effect of Temperature on Solubility An increase in temperature always shifts the position of an equilibrium to favor an endothermic process heat of solution > 0 heat of solution < 0

16. Figure 10.4 (Solubility Curves – pg 12)

17. Effect of pressure on Solubility • Pressure has a major effect on the solubility of a gas in a liquid, but little effect on other systems • Henry’s Law - At low to moderate pressure, the concentration of a gas increases with the pressure

18. Solubility Effects of Pressure

19. Colligative Properties of Nonelectrolytes • The properties of a solution may differ considerably from those of the pure solvent • Some of these properties depend on the concentration of dissolved particles and not on their nature

20. Boiling and Freezing Point • Boiling point elevation and freezing point lowering are both colligative properties • Kf is the freezing point lowering constant • Kb is the boiling point elevation constant

21. FPL and BPE Constants for Water • For water, • Kf = 1.86 • Kb= 0.52

22. Example 10.7

23. Molal Constants

24. Determination of Molar Masses from Colligative Properties molality = moles of solute/kg of solvent MMsolute = grams/moles

25. Example 10.9

26. Colligative Properties of Electrolytes When an electrolyte dissolves it breaks apart into ions. NaCl(s) Na+1(aq) + Cl-1(aq) So for every NaCl formula unit 2 aqueous ions are formed The formula is adjusted to reflect the number of ions: ∆T = k m i i = the number of ions formed

27. Example 10.10

28. Solution Stoichiometry Example

29. Solution Stoichiometry Example