Lecture 152/23/07. Quiz 5 1. A 0.03 M solution of an acid (HA) produces a pH of 4.5. What is the K a of the acid? 2. If you mix equal amounts of HCl and.

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Lecture 152/23/07

Quiz 5 1. A 0.03 M solution of an acid (HA) produces a pH of 4.5. What is the K a of the acid? 2. If you mix equal amounts of HCl and KF, will the pH be 7, below 7, or above 7?

Molecular structure and acid strength H-O-Z HOClHOBrHOI KaKa 3.5 x x x electronegativityCl (3.0)Br (2.8)I (2.5) Oxoacids with different central atoms

HOClHClO 2 HClO 3 HClO 4 KaKa 3.5 x x ~ 10 3 ~ 10 8 HNO 2 vs. HNO 3 H 2 SO 3 vs. H 2 SO 4 Molecular structure and acid strength Oxoacids with the same central atom

Acid strength related to R C 5 H 11 -COOHCH 3 -COOHCH 2 Cl-COOHCCl 3 -COOH KaKa 1.4 x x x x hexanoic acidAcetic acid Chloroacetic acid trichloroacetic acid Carboxylic Acids (R-COOH)

Assign pH: (≤ 2, 2-6, 6-8, 8-12, ≥ 12) No calculators 0.01 M solutions  HNO 2  NH 4 Cl  NaF  Mg(CH 3 COO - ) 2  BaO  KHSO 4  NaHCO 3  BaCl 2

Put in order high pH to low (0.1 M solutions) KNO 3 Na 2 SO 4 CaO HBr C 6 H 5 COOH NaH

What is a buffer?

pH of a buffer system What is the pH of a buffer that is 0.12 M lactic acid HC 3 H 5 O 3 and 0.1 M sodium lactate? K a = 1.4 x 10 -4

pH using Henderson-Hasselbach Equation What is the pH of a buffer that is 0.12 M lactic acid HC 3 H 5 O 3 and 0.1 M sodium lactate? K a = 1.4 x 10 -4