1. Chapter 8 Solutions, Acids, and Bases

3. 8.1 Formations of Solutions

4. Formation of Solutions For a solution to form, one substance must dissolve in another Remember that a solution is a homogeneous mixture

5. Dissolving A solution has two parts: 1.a solute which is the substance that is dissolved 2.a solvent which is what the solute dissolves in solutes and solvents can be any state of matter

6. Examples Solute SolventSolution Oxygen (g)Nitrogen (g)Air (g) CO 2 (g)Water (l)Soda pop (l) Glycol (l)Water (l) Antifreeze (l) Salt (s)Water (l)Ocean water (l) Zinc (s)Copper (s)Brass (s)

7. The solutions most familiar have water as a solvent Substances can dissolve in water in three ways – dissociation, dispersion, and ionization

8. DISSOCIATION Polar water molecule pull the ions in an ionic compound apart. p. 229 http://www.youtube.com/watch?v=gN9euz9jz wc&feature=player_detailpage

9. DISPERSION A solute breaks into small pieces that spread throughout the water evenly (fig. 4, p. 230)

10. IONIZATION Occurs when the solute and the solvent lose or gain electrons and it involves a chemical change

11. Properties of Liquid Solutions Physical properties of a solution that differ from those of the solute and the solvent CONDUCTIVITY – when ions are dissolved they can move freely and therefore conduct electricity FREEZING POINT – the presence of ions in water interfere with its freezing process and cause the freezing point to lower (the solution will freeze at a lower temperature) BOILING POINT – solutions also have higher boiling points than the solvent alone

12. Heat of Solution When solutions are formed, energy is either released or absorbed (hot packs and cold packs (p. 233) Endothermic – heat is absorbed Exothermic – heat is released

13. Factors Affecting Rates of Dissolving Affect how quickly a solution forms SURFACE AREA – the greater the surface area of the solute the quicker the solution forms be cause there are more places for collisions to take placeEX: crushed solutes dissolve faster (think powdered drinks) STIRRING – increases that rate at which a solution forms because the solute is moving around and colliding more TEMPERATURE – increasing temperature increases the rate at which a solution forms because the particles move faster and collide more often

14. 8.2 Solubility and Concentration

15. Solubility Solubility is the maximum amount of solute that dissolves in a given amount solvent at a constant temperature Saturated solutions contain as much solute as a solvent will hold at a given temperature; if you add more solute it will not dissolve Unsaturated solutions have less than they can hold; if you add more it will dissolve Supersaturated solutions contain MORE solute than they can normally hold at a given temperature; if you add more solute, even one crystal, all of the extra solute will come out of solution

16. Factors Affecting Solubility Solubility -how much will dissolve POLARITY OF SOLVENT – “like dissolves like” polar solvents dissolve polar solutes and nonpolar solvents dissolve nonpolar solutes EX: oil and water TEMPERATURE – increasing temperature usually increases solubility, but it decreases the solubility of gases PRESSURE – increasing pressure increases the solubility of a gas (carbonated drinks)

17. Concentration The amount of solute dissolved in a specific amount of solvent High concentration means there is a lot of solute in the solvent and low concentration means there is a small amount of solute in a solvent Percent by volume = volume of solute/volume of solution x 100% Percent by mass = mass of solute/mass of solution x 100%

18. 8.3 Properties of Acids & Bases

19. Acids An ACID is a compound that produces HYDRONIUM IONS (H 3 O + ) when dissolved in water Ex. HCl + H 2 O → H 3 O + + Cl - Acids generally 1. TASTE SOUR 2. REACT WITH SOME METALS Ex. HCl + Zn → ZnCl + H 2 3. CHANGE COLOR OF INDICATORS

20. Bases A BASE is a compound that produces HYDROXIDE IONS (OH - ) when dissolved in water Ex. NaOH → Na + + OH - Bases generally 1. TASTE BITTER 2. FEEL SLIPPERY

21. Indicators --An INDICATOR is usually a weak acid or base that changes color when in an acidic or basic solution Common indicators include 1. LITMUS PAPER (RED AND BLUE) Note-acids turn blue litmus red; bases turn red litmus blue 2. PHENOLPHTHALEIN colorless in acidic solution; pink in basic solution

22. A NEUTRALIZATION REACTION is the reaction between an acid and a base; PRODUCES WATER AND A SALT Ex. NaOH + HCl → NaCl + HOH Common salts not only include NaCl, but salts of other acid-base neutralizations p. 244

23. 8.4 Strength of Acids and Bases

24. pH Scale The pH SCALE is a number scale that usually ranges from 0 to 14 and is a measure of H 3 O + concentration SEE FIG. 22, P. 247

25. Water undergoes AUTO-IONIZATION and produces H 3 O + and OH - ions H 2 O → H + + OH - In PURE WATER OR NEUTRAL SOLUTION (AT 25 o C) 1. H + = OH - 2. pH = 7 In an ACIDIC SOLUTION 1. H + > OH - 2. pH < 7 In a BASIC SOLUTION 1. H + 7

26. A STRONG ACID is one that ionizes completely in water; a STRONG BASE dissociates completely Ex. HCl, NaOH A WEAK ACID is one that partially ionizes in water; a WEAK BASE partially ionizes in water Ex. CH 3 COOH, NH 3

27. Buffer A BUFFER is a solution that resists large changes in pH A buffer is a solution of 1. a weak acid and its salt Or 2. a weak base and its salt

28. Electrolyte An ELECTROLYTE is a substance that produces ions when dissolved in water (salts, acids, bases) Strong acids, strong bases, and soluble salts are strong electrolytes, because they ionize or dissociate completely; weak acids, weak bases, and insoluble salts are weak electrolytes