Exam_3_2007_A_key

# Exam_3_2007_A_key - EAS 1600 INTRODUCTION TO ENVIRONMENTAL...

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EAS 1600 - INTRODUCTION TO ENVIRONMENTAL SCIENCES Fall, 2007 Exam 3 - 11/30/07 < Answer all Questions < Show all your work < Place your name on each page < This is a closed-book exam, notes are not allowed; all are expected to comply with the Georgia Tech Honor Code. Please also note that cell phone use or contact with any other person is not allowed. I am aware and in compliance with the Georgia Tech Honor Code and I agree to abide by the grading policies of this class. Signature: ____________________________________________________________ Print Name: ___________________________________________________________ Lab Section: ___________________ A 1

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1. Consider two aqueous solutions of HCl one contains 5 x 10 -3 mole/l of HCl, the second solution contains 1 x 10 -14 mole/l of HCl. What is the pH of each solution (5 pts). 1) H + = 5 x 10 -3 mole/l, pH = -log(5 x 10 -3 ) = 2.3 2) Remember H + in pure water = 10 -7 mole/l, so H + from HCl is negligible and pH = 7 2. a. Consider a solution of 0.01 mole/l of hydrofluoric acid (HF). What is the pH of the solution? (5 pts) K a for hydrofluoric acid = 3 x 10 -5 [H + ] 2 = 0.01(3 x 10 -5 ) [H + ] = 5.5 x 10 -4 pH = 3.3 b. What would the pH of the solution above be if you were to add 0.01 mole/l of sodium fluoride, NaF, a strong electrolyte which completely dissociates in water? (5 pts) pH = 4.5 2
c. What would the pH of the solution above be (i.e. 0.01 mole/l of both HF and NaF) if

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## This note was uploaded on 02/08/2011 for the course EAS 1600 taught by Professor Jimstjohn during the Fall '08 term at Georgia Tech.

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Exam_3_2007_A_key - EAS 1600 INTRODUCTION TO ENVIRONMENTAL...

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