Chapter 20

DefinitionsAcid: any substance that produces H + in solution e.g.:HCl (g) H + (aq) Cl - (aq) (H 2 SO 4, vinegar, lemon juice) Base: any substance that produces OH - in solution e.g.:NaOH (s) Na + (aq) OH - (aq) (KOH, detergents, oven cleaner)

CharacteristicsAcidsBases taste sour taste bitter react with metals producing H 2 gas feel slippery produce H + produce OH - conduct electricity

Neutralization Reactions whenever an acid reacts with a base, a neutralization reaction takes place. e.g.: HCl (aq) H 2 O (l) NaCl (aq) net ionic equation: H 2 O (l) H + (aq) OH - (aq) NaOH (aq) HCl (aq) baseacidwatersalt

Acid / Base Titrations a solution of base (NaOH) with known concentration is used to determine the concentration of acid (HCl) in another solution. e.g.: HCl (aq) H 2 O (l) NaCl (aq) NaOH (aq) standardunknown

Acid / Base Titrations continued an acid / base indicator (or pH meter) is used to identify when all of the acid in an unknown sample has been neutralized by the base. the number of moles of OH - equals the number of moles of H + when the pH = 7 (neutral) Problem: It takes 35.0 mL of 6.0 M NaOH to neutralize the acid in a 750 mL HCl solution of unknown concentration. What is the concentration of the HCl solution?

Titration Problem Solution HCl (aq) H 2 O (l) NaCl (aq) NaOH (aq) = 0.21 molmoles NaOH = L6.0 M moles of OH - equal moles of H + when neutral moles OH - = 0.21 mol therefore, moles H + = 0.21 mol NaOH (aq) Na + (aq) OH - (aq) HCl (aq) H + (aq) Cl - (aq) = moles HCl [HCl] = 0.21 mol L = 0.28 M

Assignment In Class: In Class: Page 595 Page 595 Questions 1-5 Questions 1-5 Homework: Homework: Read Experiment 13C (pp ) Read Experiment 13C (pp ) There will be a Pre-Lab Quiz There will be a Pre-Lab Quiz Online Titration Tutorial Assignment Online Titration Tutorial Assignment