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I. Introduction to Acids & Bases

Acids & Bases. I. Introduction to Acids & Bases. electrolytes  electrolytes. A. Properties. ACIDS. BASES. sour taste. bitter taste. turn blue litmus red. turn red litmus blue. react with metals to form H 2 gas. slippery feel. vinegar, milk, soda, apples, citrus fruits.

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I. Introduction to Acids & Bases

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  1. Acids & Bases I. Introduction toAcids & Bases

  2. electrolytes electrolytes A. Properties ACIDS BASES • sour taste • bitter taste • turn blue litmus red • turn red litmus blue • react with metals to form H2 gas • slippery feel • vinegar, milk, soda, apples, citrus fruits • ammonia, lye, antacid, baking soda ChemASAP

  3. H H – + O O Cl Cl H H H H B. Definitions • In aqueous solution… • Acidsform hydronium ions (H3O+) HCl+ H2O  H3O+ + Cl– acid

  4. H H – + N O O N H H H H H H H H B. Definitions • In aqueous solution… • Bases form hydroxide ions (OH-) NH3+ H2O  NH4+ + OH- base

  5. - + C. Strength • Strong Acid/Base • 100% ionized in water • strong electrolyte HCl HNO3 H2SO4 HBr HI HClO4 NaOH KOH Ca(OH)2 Ba(OH)2

  6. - + C. Strength • Weak Acid/Base • does not ionize completely • weak electrolyte HF CH3COOH H3PO4 H2CO3 HCN NH3

  7. Acids & Bases II. pH

  8. H2O + H2O H3O+ + OH- A. Ionization of Water Kw = [H3O+][OH-] = 1.0  10-14 Kw = ion-product constant for water

  9. A. Ionization of Water • Find the hydroxide ion concentration of 3.0  10-2 M HCl. [H3O+][OH-] = 1.0  10-14 [3.0  10-2][OH-] = 1.0  10-14 [OH-] = 3.3  10-13 M Acidic or basic? Acidic

  10. pouvoir hydrogène (Fr.) “hydrogen power” B. pH Scale 14 0 7 INCREASING BASICITY INCREASING ACIDITY NEUTRAL pH = -log[H3O+]

  11. B. pH Scale pH of Common Substances

  12. B. pH Scale pH = -log[H3O+] pOH = -log[OH-] pH + pOH = 14

  13. B. pH Scale • What is the pH of 0.050 M HNO3? pH = -log[H3O+] pH = -log[0.050] pH = 1.3 Acidic or basic? Acidic

  14. Example pH (pOH) calculations • If you had a sol’n with the concentration of 0.025 M [H3O+], what is the sol’ns pH? What is the sol’ns pOH? 1. Given: [H3O+] = 0.025 M Unknown: pH = ?? • pH = -log [H3O+] = -log[0.025M] = 1.6 • pOH = 14 – pH = 14 - 1.6 = 12.4

  15. Example pH (pOH) calculations B. What is the pH of 0.070 M HNO3? Is it acidic or basic? • pH = -log[H3O+] • pH = -log[0.070] = 1.15 • It is acidic because 1.15  7.

  16. Example pH (pOH) calculations C. What is the pH of a 0.100 M HCl sol’n? • Given: Identity Concentration: [0.100 M] Unknown: pH = ???? 2. [H3O+] = 0.100 M pH = -log[0.100 M] = 1.00

  17. Example pH (pOH) calculations D. What is the pH of a 1.5 M sol’n of KOH? (this is a base) 1. Given: [1.5 M] Unknown: pH = ???? 2. pOH = - log [OH-] pOH = - log [1.5] pOH = -0.18 3. pH + pOH = 14 14 – pOH = pH 14- (-0.18) = 14.18 pH = 14.18 Check : Answer does indicate that KOH forms a sol’n pH  7, which is basic.

  18. Acids & Bases III. Titration

  19. A. Neutralization • Chemical reaction between an acid and a base. • Products are a salt (ionic compound) and water.

  20. A. Neutralization ACID + BASE  SALT + WATER HCl + NaOH  NaCl + H2O strong strong neutral HC2H3O2 + NaOH  NaC2H3O2 + H2O weak strong basic • Salts can be neutral, acidic, or basic. • Neutralization does not mean pH = 7.

  21. standard solution unknown solution B. Titration • Titration • Analytical method in which a standard solution is used to determine the concentration of an unknown solution.

  22. B. Titration • Equivalence point (endpoint) • Point at which equal amounts of H3O+ and OH- have been added. • Determined by… • indicator color change • dramatic change in pH

  23. B. Titration moles H3O+ = moles OH- MVn = MVn M: Molarity V: volume n: # of H+ ions in the acid or OH- ions in the base

  24. B. Titration • 42.5 mL of 1.3M KOH are required to neutralize 50.0 mL of H2SO4. Find the molarity of H2SO4. H3O+ M = ? V = 50.0 mL n = 2 OH- M = 1.3M V = 42.5 mL n = 1 MV# = MV# M(50.0mL)(2) =(1.3M)(42.5mL)(1) M = 0.55M H2SO4

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