1 Properties of Acids Have a sour taste. Vinegar owes its taste to acetic acid. Citrus fruits contain citric acid. React with certain metals to produce hydrogen gas. React with carbonates and bicarbonates to produce carbon dioxide gas Cause color changes in plant dyes. 2HCl (aq) + Mg (s) MgCl 2 (aq) + H 2 (g) 2HCl (aq) + CaCO 3 (s) CaCl 2 (aq) + CO 2 (g) + H 2 O (l) Aqueous acid solutions conduct electricity.

2 Have a bitter taste. Feel slippery. Many soaps contain bases. Properties of Bases Cause color changes in plant dyes. Aqueous base solutions conduct electricity. Examples:

3 Arrhenius acid is a substance that produces H + (H 3 O + ) in water Arrhenius base is a substance that produces OH - in water

4 Hydronium ion, hydrated proton, H 3 O +

5 A Brønsted acid is a proton donor A Brønsted base is a proton acceptor acidbaseacidbase A Brønsted acid must contain at least one ionizable proton!

6 Monoprotic acids HCl H + + Cl - HNO 3 H + + NO 3 - CH 3 COOH H + + CH 3 COO - Strong electrolyte, strong acid Weak electrolyte, weak acid Diprotic acids H 2 SO 4 H + + HSO 4 - HSO 4 - H + + SO 4 2- Strong electrolyte, strong acid Weak electrolyte, weak acid Triprotic acids H 3 PO 4 H + + H 2 PO 4 - H 2 PO 4 - H + + HPO 4 2- HPO 4 2- H + + PO 4 3- Weak electrolyte, weak acid

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8 Identify each of the following species as a Brønsted acid, base, or both. (a) HI, (b) CH 3 COO -, (c) H 2 PO 4 - HI (aq) H + (aq) + I - (aq)Brønsted acid CH 3 COO - (aq) + H + (aq) CH 3 COOH (aq)Brønsted base H 2 PO 4 - (aq) H + (aq) + HPO 4 2- (aq) H 2 PO 4 - (aq) + H + (aq) H 3 PO 4 (aq) Brønsted acid Brønsted base

9 Neutralization Reaction acid + base salt + water HCl (aq) + NaOH (aq) NaCl (aq) + H 2 O H + + Cl - + Na + + OH - Na + + Cl - + H 2 O H + + OH - H 2 O

10 Neutralization Reaction Involving a Weak Electrolyte weak acid + base salt + water HCN (aq) + NaOH (aq) NaCN (aq) + H 2 O HCN + Na + + OH - Na + + CN - + H 2 O HCN + OH - CN - + H 2 O

11 Neutralization Reaction Producing a Gas acid + base salt + water + CO 2 2HCl (aq) + Na 2 CO 3 (aq) 2NaCl (aq) + H 2 O +CO 2 2H + + 2Cl - + 2Na + + CO Na + + 2Cl - + H 2 O + CO 2 2H + + CO 3 2- H 2 O + CO 2

Sr 2+ ( aq ) + 2OH - ( aq )+ 2H + ( aq )+ 2ClO 4 - ( aq ) 2H 2 O( l )+Sr 2+ ( aq )+2ClO 4 - ( aq ) Sr 2+ ( aq ) + 2OH - ( aq )+ 2H + ( aq )+ 2ClO 4 - ( aq ) 2H 2 O( l )+Sr 2+ ( aq )+2ClO 4 - ( aq ) Ba 2+ ( aq ) + 2OH - ( aq )+ 2H + ( aq )+ SO 4 2- ( aq ) 2H 2 O( l )+Ba 2+ ( aq )+SO 4 2- ( aq ) Sample Problem 4.4 Writing Ionic Equations for Acid-Base Reactions PROBLEM: Write balanced molecular, total ionic, and net ionic equations for each of the following acid-base reactions and identify the spectator ions. reactants are strong acids and bases and therefore completely ionized in water PLAN:SOLUTION: (a) Sr(OH) 2 ( aq )+2HClO 4 ( aq ) 2H 2 O( l )+Sr(ClO 4 ) 2 ( aq ) 2OH - ( aq )+ 2H + ( aq ) 2H 2 O( l ) (a) strontium hydroxide( aq ) + perchloric acid( aq ) (b) barium hydroxide( aq ) + sulfuric acid( aq ) (b) Ba(OH) 2 ( aq ) + H 2 SO 4 ( aq ) 2H 2 O( l ) + BaSO 4 ( aq ) 2OH - ( aq )+ 2H + ( aq ) 2H 2 O( l ) products are water spectator ions

Figure 4.7 An acid-base titration. Start of titration Excess of acid Point of neutralization Slight excess of base

Sample Problem 4.5Finding the Concentration of Acid from an Acid-Base Titration PROBLEM: You perform an acid-base titration to standardize an HCl solution by placing mL of HCl in a flask with a few drops of indicator solution. You put M NaOH into the buret, and the initial reading is 0.55 mL. At the end point, the buret reading is mL. What is the concentration of the HCl solution? PLAN: SOLUTION: volume(L) of base mol of base mol of acid M of acid multiply by M of base molar ratio divide by L of acid NaOH( aq ) + HCl( aq ) NaCl( aq ) + H 2 O( l ) ( ) mL x 1L 10 3 mL = L LX M= 5.078x10 -3 mol NaOH Molar ratio is 1: x10 -3 mol HCl L = M HCl

Figure 4.8 An aqueous strong acid-strong base reaction on the atomic scale.