I. Introduction to Acids & Bases Acids & Bases

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

B. Definitions  In aqueous solution… HCl + H 2 O  H 3 O + + Cl – AcidsAcids form hydronium ions (H 3 O + ) H HHHH H Cl OO – + acid

B. Definitions  In aqueous solution… BasesBases form hydroxide ions (OH - ) NH 3 + H 2 O  NH OH - H H H H H H N NO O – + H H H H base

C. Strength  Strong Acid/Base 100% ionized in water strong electrolyte - + HCl HNO 3 H 2 SO 4 HBr HI HClO 4 NaOH KOH Ca(OH) 2 Ba(OH) 2

C. Strength  Weak Acid/Base does not ionize completely weak electrolyte - + HF CH 3 COOH H 3 PO 4 H 2 CO 3 HCN NH 3

Acids & Bases II. pH

A. Ionization of Water H 2 O + H 2 O H 3 O + + OH - K w = [H 3 O + ][OH - ] = 1.0  K w = ion-product constant for water

A. Ionization of Water  Find the hydroxide ion concentration of 3.0  M HCl. [H 3 O + ][OH - ] = 1.0  [3.0  ][OH - ] = 1.0  [OH - ] = 3.3  M Acidic or basic? Acidic

pH = -log[H 3 O + ] B. pH Scale 0 7 INCREASING ACIDITY NEUTRAL INCREASING BASICITY 14 pouvoir hydrogène (Fr.) “hydrogen power”

B. pH Scale pH of Common Substances

B. pH Scale pH = -log[H 3 O + ] pOH = -log[OH - ] pH + pOH = 14

B. pH Scale  What is the pH of M HNO 3 ? pH = -log[H 3 O + ] pH = -log[0.050] pH = 1.3 Acidic or basic? Acidic

Example pH (pOH) calculations A. If you had a sol’n with the concentration of M [H 3 O + ], what is the sol’ns pH? What is the sol’ns pOH? 1. Given: [H 3 O + ] = M Unknown: pH = ?? 2.pH = -log [H 3 O + ] = -log[0.025M] = pOH = 14 – pH = = 12.4

Example pH (pOH) calculations B. What is the pH of M HNO 3 ? Is it acidic or basic? 1.pH = -log[H 3 O + ] 2.pH = -log[0.070] = It is acidic because 1.15  7.

Example pH (pOH) calculations C. What is the pH of a M HCl sol’n? 1.Given: Identity Concentration: [0.100 M] Unknown: pH = ???? 2. [H 3 O + ] = M pH = -log[0.100 M] = 1.00

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 = pH + pOH = – pOH = pH 14- (-0.18) = pH = Check : Answer does indicate that KOH forms a sol’n pH  7, which is basic.

III. Titration Acids & Bases

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

A. Neutralization ACID + BASE  SALT + WATER HCl + NaOH  NaCl + H 2 O HC 2 H 3 O 2 + NaOH  NaC 2 H 3 O 2 + H 2 O Salts can be neutral, acidic, or basic. Neutralization does not mean pH = 7. weak strong neutral basic

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

 Equivalence point (endpoint) Point at which equal amounts of H 3 O + and OH - have been added. Determined by… indicator color change B. Titration dramatic change in pH

B. Titration moles H 3 O + = 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

B. Titration  42.5 mL of 1.3M KOH are required to neutralize 50.0 mL of H 2 SO 4. Find the molarity of H 2 SO 4. H3O+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 H 2 SO 4