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Problem Set 6 - Chem 215 Fall 2007 ed Ch 8 71 81 83 93 Ch...

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Chem 215, Fall 2007 Problem Set 6 Due Friday, Oct. 12, 2:00 PM ed Ch 8: 71, 81, 83, 93 Name: ___________________________ Ch 10:13, 19, 25, 31, 41, 51 Undergrad TA Name: _________________________ Lab Day: ________________________ 1. The K sp for Cu(OH) 2 is 1.6 x 10 -19 . The complex Cu(NH 3 ) 4 2+ is produced by mixing Cu 2+ with ammonia: Cu 2+ (aq) + 4NH 3 (aq) Cu(NH 3 ) 4 2+ (aq) K = 1.0 x 10 13 a) Calculate the equilibrium constant for the following reaction: Cu(OH) 2 (s) + 4NH 3 (aq) Cu(NH 3 ) 4 2+ (aq)+ 2OH - (aq) b) Calculate the solubility (in mol/L) of Cu(OH) 2 in 3.0 M NH 3 (aq).
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Chem 215, Fall 2007 Problem Set 6 Due Friday, Oct. 12, 2:00 PM 2. Sand is primarily silica, SiO 2 . It can react with water to form silicic acid: SiO 2 (s) + 2H 2 O(l) H 4 SiO 4 (aq) K = 2 x 10 -3 Silicic acid is a weak acid: H 4 SiO 4 (aq) + H 2 O H 3 SiO 4 - (aq) + H 3 O + (aq) pK a = 9.46 a) Will silica be more soluble in an acidic or basic solution? Why? b) Calculate the molar solubility (in mol/L) of silica at a pH of 7.0 and a pH of 10.0.
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