CHEM 121 Chapter 9 Winter 2014

Acids produce H+ ions Naming: HCl (g) : For polyatomic ion acids:

Bases Bases: donate OH- ions NaOH (s)

Acids & Bases Brønsted-Lowry Acids: HCl + H2O  Brønsted-Lowry Bases: NH3 + H2O  Conjugate acid-base pairs: HA + B

3-minute Practice What is conjugate acid of I-? What is the conjugate base of CH3COOH?

Strong Acids & Bases

Weak Acids & Bases H2O + NH3 + Reaction will favor side with weaker acid

Dissociation Constants Equilibrium constants for weak acids and bases HA (aq) + H2O (l) +

Dissociation of Water Water is ______________ H2O (l) + pure water: Kw =

3-minute Practice Calculate the concentration of hydroxide ions in coffee, an aqueous solution containing 1.0 x 10-5 M H3O+ ions Calculate the concentration of hydroxide ions in milk, which contains 5.0 x 10-7 M H3O+ ions

The pH Scale Scale from ________ Acidic Neutral Basic Milk: [H3O+] = 5.0 x 10-7 M pH of milk =

3-minute Practice Calculate the pH of a solution that has… [H3O+] = 1.0 x 10-8 M [OH-] = 4.0 x 10-2 M

Neutralization Example: Reactants: Products: HCl (aq) + NaOH (aq)  http://www.youtube.com/watch?v=u9nOIZDdvRw Molecular equation: Net ionic equation:

Other Acid Reactions Example: carbonates bicarbonates Products: NaHCO3 (aq) + HCl (aq) 

Acid & Active Metals Example: calcium solid + HCl Zn and HCl

Titration Indicator: Equivalence Point: End Point: Pink (basic) Colorless (acidic) Equivalence Point: End Point:

Titration Calculations 25.0 mL HCl solution is titrated with 15.5 mL 0.200 M NaOH to reach the equivalence point. What is the molarity of the HCl? mols base? mols acid? Acid concentration?

Buffers Acid must neutralize __________________________ Base must neutralize __________________________ Acid and base must not __________________________ Use a weak acid and its salt

Buffers CH3COOH (aq) + H2O (l) CH3COO - (aq) + H3O+ (aq) You have prepared a buffer with 0.90 M CH3COOH and 1.2 M CH3COO-. (Ka for acetic acid = 1.8 x 10-5). What is the equilibrium expression for this buffer? What is the [H3O+] in this solution? What is the pH of this solution?