EAS 1600 - INTRODUCTION TO ENVIRONMENTAL SCIENCES Fall, 2008 Exam 3 - 11/24//08 <Answer all Questions <Show allyour 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: ___________________ B1
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1. An aqueous solutions has a pH of 11.5. What is the H+concentration in the solution? (5 pts) pH = -log[H+] 11.5 = -log[H+] [H+] = 10-11.5= 3 x 10-12 2. a. A solution contains carbonic acid (H2CO3) and bicarbonate (HCO3-). The carbonic acid has a concentration of 0.1 mole/l and bicarbonate is 10 times larger. What is the pH of the solution? (10 pts) H2CO3H+HCO3-0.1 0 1 -x +x +x 0.1- x x 1+ x 7323103.4]][[−−+=xCOHHCOH(this could be neglected-very small) 7103.41.0)1)((−=−+xxxx8103.4−=xx37.7)103.4log(8=⇒=−pHxpHb. Is the solution above buffered? Why? (5 pts) yes, it contains a weak acid and its conjugate base i.e. carbonic acid and bicarbonate 2