ws6s08vkey

# ws6s08vkey - CH302 Spring 2007 Worksheet 6 1 How many mL of...

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CH302 Spring 2007 Worksheet 6+ 1. How many mL of a 0.1 M solution of Ca(OH) 2 are required to neutralized 200 mL of a 0.2 M solution of HNO 3 ? 200 mL of a .2M solution of HNO 3 will have (.2L)(.2 mol/L) = 0.04 moles H + to get .04 moles OH - you’ll need 200 mL (V)(.1moles Ca(OH) 2 /L)(2 moles OH - /1 moles Ca(OH 2 ) = 0.04 moles of OH - V = .2L or 200 mL 2. The pK a of the amino acid aspartic acid is 4. In a solution in which the pH = 7.5 what fraction of the aspartic acid is protonated? A. 0.03% B. 7% C. 23.4% D. 72% E. 99.5% pK a = pH – log([A - ]/[HA]) 4 = 7.5 - log([A - ]/[HA]) [A - ]/[HA] = 3162 [HA]/([HA]+[A - ]) = 1/3163 = 0.0003 or .03% alternatively you know the pH is more than 3 pH units away from the pK so the protonated must be less than .1%. 3. At what pH would the aspartic acid be 50% protonated? When the pH = pK a the concentration of [A - ] = [HA] so pH = 4 4. The K sp of magnesium hydroxide is 1.8 x 10 -11 . What is the pH of saturated solution of magnesium hydroxide in 0.01 M HCl?

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ws6s08vkey - CH302 Spring 2007 Worksheet 6 1 How many mL of...

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