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01 - Problems

# 01 - Problems - 2 Calculate[H and pH of a 0.1F solution of...

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Fall 2010 Chem 15 Prof. L.G.Moretto Problem set #1 DUE Sept. 30 This is some homework for your delight and to prepare you for the forthcoming midterm . 1. Acidimetric stoichiometry. Identify the resulting solutions (e.g. diprotic acid, buffer, ampholyte, ect.), determine their formal composition, and calculate [H + ] and pH with the simplest approximation. The following solutions are given: H 2 A (a); NaHA(b); Na 2 A(c); HCl (d); NaOH(e). K 1a = 10 -4 , K 2a = 10 -8 . All solutions are 0.1F i. 30 ml of (a) + 30 ml of (c) ii. 20 ml of (a) + 10 ml of (b) iii. 20 ml of (c) + 5 ml of (d) iv. 20 ml of (b) + 20 ml of (e)
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Unformatted text preview: 2. Calculate [H + ] and pH of a 0.1F solution of Na 2 A (same acid as in problem 1). Please, justify explicitly all approximations. Do not neglect the 2 nd dissociation. 3. Derive an expression for [H + ] for a mixture of two weak monoprotic acids with dissociation constants K 1 , K 2 and formal concentrations c 1 , c 2 . Come up with useful approximations. 4. How many ml of solution (e) should you add to 20ml of solution (a) in problem 1) in order to get pH=4? Do it the hard way and check your result with the easy way. 5. Write charge and mass balance of a 0.1F solution of NaHSO 4 ....
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