1. Chemistry in Water Chem Rxns in Aqueous Solns Solvent = Water Solute = acid, base or salt

2. IONIC COMPOUNDS Salt: constituent ions form solid crystal lattice, high MP, dissolves in H 2 O to give cations (+) and anions (-) surrounded by polar H 2 O molecules (Fig 11.1) Acid: produces H + in water, sour in taste –HBr  H + + Br - Base: produces OH - in water, bitter in taste –KOH  K + + OH -

4. ACIDS (1) Acids produce H + cations in an aqueous soln. Monoprotic acids give up to one H + ion per acid (*HCl-hydrochloric, *HNO 3 -nitric, HBr- hydrobromic) Diprotic acids give up to two H + ions per acid (*H 2 SO 4 -sulfuric). Triprotic (H 3 PO 4 -phosphoric). See uses of acids on pp 420-421, 424-25 * You are using in lab

5. ACIDS (2) All acids on previously slide but phosphoric acid are strong acids meaning they ionize completely in water. –HBr  H + + Br - strong acid; every HBr ionizes. We say that the reaction is complete meaning essentially no reactant exists.

6. ACIDS (3) Weak acids do not ionize completely. –HF ↔ H + + F - weak acid –Only 1 per 100 HF ionizes. We say that HF and its constituent ions are in equilibrium meaning both reactants and products exist in balance. –Other weak acids: HNO 2 -nitrous, H 2 SO 3 - sulfurous, phosphoric, organic acids

7. Molarity (1) Concentration unit reflecting amount of solute in solvent Molarity = M = mole solute/liter soln Mole = number of 12 C atoms in exactly 12 g of 12 C = Avogadro’s number = 6.02E23 Let’s consider concentration of H + ions in water = [H + ]. 1 g H + = 1 mol H + Also 1 liter = 1 L = 1000 mL

8. Molarity (2) 0.001 mol [H + ] in 1 L soln has a molarity of 0.001 mol/1 L = 0.001 M or 1E-3 M. 0.000001 mol [H + ] in 0.1 L soln is 1E-5 5E-3 mol [H + ] in 1 L soln is 5E-3 M 2.34E-4 mol [H + ] in 1 L soln is 2.34E-4 M 4E-8 mol [H + ] in 0.5 L soln is 8E-8 M Ex 11.4: 0.050 g H + in 0.50 L yields [H + ] = 0.050 mol/0.50 L = 0.1 M

9. pH SCALE Another way to describe [H + ] is to use the pH scale where molarity is expressed as 1.0 x 10 -pH. Note that pH is the negative of the exponent meaning that pH is positive. –1E-3 M has pH = 3 –1E-5 has pH = 5 –5E-3 M = 1E-2.30 M has pH = 2.30 –2.34E-4 M = 1E-3.63 M has pH 3.63 –8E-8 M = 1E-7.10 M has pH = 7.10

10. pH SCALE (3) The pH scale goes from 1 to 14 corresponding to10 -1 M (very high [H + ]; pH = 1) to 10 -14 M (very low [H + ]; pH = 14). pH = 7 is a neutral solution pH < 7 means acidic Figure 11.9

12. BASES Bases produce OH - anions in an aqueous soln OH - anion is the hydroxide ion Strong bases ionize completely –LiOH  Li + + OH - Weak bases ionize to a small degree –Ca(OH) 2 ↔ Ca 2+ + 2OH - –NH 3 + H 2 O ↔ NH 4 + + OH - –CO 3 2- + H 2 O ↔ HCO 3 - + OH - Uses on pp 428-430

14. pH and Bases If [H + ] > 1.0E-07 M or pH < 7, solution is acidic If [H + ] 7, solution is basic In an aqueous soln, [H + ] x [OH - ] = 1.0E-14 Pure Water has [H + ] = [OH - ] = 1.0E-07, is neutral and has a pH = 7 Figure 11.9

15. pH and Plants pH Affects Nutrient, Minerals and Growth http://www.esf.edu/pubprog/brochure/soilp h/soilph.htm Antacids

16. ACID-BASE NEUTRALIZATION (1) H + + OH - ↔ H 2 O –An equilibrium is established –Neutralization  –Self ionization  Acid + Base  Salt + Water –HCl + NaOH  NaCl + H 2 O

18. Hyponatremia Duluth News-Tribune The Pittsburgh Channel Feb 4, 2005 Water of Life, Water of Death http://www.mashinc.org/resources-essay- water.html http://www.mashinc.org/resources-essay- water.html Acid-Base Balance http://www.e-kidneys.net/acidbase.html

19. Gatorade Development of Gatorade http://www.rgp.ufl.edu/publications/explore /v08n1/gatorade.html http://www.rgp.ufl.edu/publications/explore /v08n1/gatorade.html Chemistry and Gatorade http://chemcases.com/gatorade/ http://chemcases.com/gatorade/