03-10-08 - Chem. 31 3/10 Lecture Announcements 1. Exam...

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Unformatted text preview: Chem. 31 3/10 Lecture Announcements 1. Exam Results: Average = 73% Score N 90-98 9 80s 17 70s 11 60s 10 50s 9 <50 7 Announcements 2. New homework assignment posted (and handed out with exam) 3. Information about tap water also now posted Announcements Parts of Exam that gave most people difficulties Solubility Product Problems - Solubility of Mg(OH) 2 in Common Ion If we dissolve Mg(OH) 2 in a common ion (OH- or Mg 2+ ), from Le Chteliers principle, we know the solubility will be reduced Example 1) What is the solubility of Mg(OH) 2 in a pH = 11.0 buffer? In this problem, because of buffer, pH is fixed, so [OH- ] also is fixed, and NO ICE TABLE NEEDED Solubility Product Problems - Solubility of Mg(OH) 2 in Common Ion Example 2) Solubility of Mg(OH) 2 in 5.0 x 10- 3 M MgCl 2 . Solubility Product Problems Precipitation Problems What occurs if we mix 50 mL of 0.020 M BaCl 2 with 50 mL of 3.0 x 10-4 M (NH 4 ) 2 SO 4 ? Does any solid form from the mixing of ions? What are the concentrations of ions remaining? Precipitations Used for Separations Example: If we wanted to know the concentrations of Ca 2+ and Mg 2+ in a water sample. EDTA titration gives [Ca in a water sample....
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This note was uploaded on 04/17/2008 for the course CHEM 31 taught by Professor Staff during the Spring '08 term at CSU Sacramento.

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03-10-08 - Chem. 31 3/10 Lecture Announcements 1. Exam...

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