To understand the process of dissolving To learn why certain substances dissolve in water

1. Objectives • To understand the process of dissolving • To learn why certain substances dissolve in water • To learn qualitative terms describing the concentration of a solution • To understand the factors that affect the rate at which a solid dissolves

2. What is a solution? • Solution – homogeneous mixture • Solvent – substance present in largest amount • Solutes – other substances in the solution • Aqueous solution – solution with water as the solvent

4. A. Solubility • Solubility of Ionic Substances • Ionic substances breakup into individual cations and anions.

5. A. Solubility • Solubility of Ionic Substances • Polar water molecules interact with the positive and negative ions of a salt.

6. A. Solubility • Solubility of Polar Substances • Ethanol is soluble in water because of the polar OH bond.

7. A. Solubility • Solubility of Polar Substances • Why is solid sugar soluble in water?

8. A. Solubility • Substances Insoluble in Water • Nonpolar oil does not interact with polar water. • Water-water hydrogen bonds keep the water from mixing with the nonpolar molecules.

9. A. Solubility • How Substances Dissolve • A “hole” must be made in the water structure for each solute particle. • The lost water-water interactions must be replaced by water-solute interactions. • “like dissolves like”

10. B. Solution Composition: An Introduction • The solubility of a solute is limited. • Saturated solution – contains as much solute as will dissolve at that temperature • Unsaturated solution – has not reached the limit of solute that will dissolve

11. B. Solution Composition: An Introduction • Supersaturated solution – occurs when a solution is saturated at an elevated temperature and then allowed to cool but all of the solid remains dissolved • Contains more dissolved solid than a saturated solution at that temperature • Unstable – adding a crystal causes precipitation

12. B. Solution Composition: An Introduction • Solutions are mixtures. • Amounts of substances can vary in different solutions. • Specify the amounts of solvent and solutes • Qualitative measures of concentration • concentrated – relatively large amount of solute • dilute – relatively small amount of solute

13. B. Solution Composition: An Introduction • Which solution is more concentrated?

14. B. Solution Composition: An Introduction • Which solution is more concentrated?

15. C. Factors Affecting the Rate of Dissolving • Surface area • Stirring • Temperature

16. Objectives • To understand mass percent and how to calculate it • To understand and use molarity • To learn to calculate the concentration of a solution made by diluting a stock solution

17. A. Solution Composition: Mass Percent

18. B. Solution Composition: Molarity • Concentration of a solution is the amount of solute in a given volume of solution.

19. B. Solution Composition: Molarity • Consider both the amount of solute and the volume to find concentration.

20. B. Solution Composition: Molarity • To find the moles of solute in a given volume of solution of known molarity use the definition of molarity.

21. B. Solution Composition: Molarity • Standard solution - a solution whose concentration is accurately known • To make a standard solution • Weigh out a sample of solute. • Transfer to a volumetric flask. • Add enough solvent to mark on flask.

22. C. Dilution • Water can be added to an aqueous solution to dilute the solution to a lower concentration. • Only water is added in the dilution – the amount of solute is the same in both the original and final solution.

23. D. Dilution • Diluting a solution • Transfer a measured amount of original solution to a flask containing some water. • Add water to the flask to the mark (with swirling) and mix by inverting the flask.

24. Objectives • To learn to solve stoichiometric problems involving solution reactions • To do calculations involving acid-base reactions • To learn about normality and equivalent weight • To use normality in stoichiometric calculations • To understand the effect of a solute on solution properties   

25. A. Stoichiometry of Solution Reactions

26. B. Neutralization Reactions • An acid-base reaction is called a neutralization reaction. • Steps to solve these problems are the same as before.

27. C. Normality • Unit of concentration • One equivalent of acid – amount of acid that furnishes 1 mol of H+ ions • One equivalent of base – amount of base that furnishes 1 mol of OH ions • Equivalent weight – mass in grams of 1 equivalent of acid or base

28. C. Normality

29. C. Normality

30. C. Normality • To find number of equivalents

31. C. Normality • Advantage of equivalents

32. D. Boiling Point and Freezing Point • The presence of solute “particles” causes the liquid range to become wider. • Boiling point increases • Freezing point decreases

33. D. Boiling Point and Freezing Point • Why does the boiling point of a solution increase? • Forming a bubble in a solution • Solute particles block some of the water molecules trying to enter the bubble. • Need higher pressure to maintain the bubble.

34. D. Boiling Point and Freezing Point • Comparing bubbles

35. D. Boiling Point and Freezing Point • Colligative property – a solution property that depends on the number of solute particles present