EAS 1600 - INTRODUCTION TO ENVIRONMENTAL SCIENCES Fall, 2006 Exam 3 - 12/1/06 <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 Signature: ____________________________________________________________ Print Name: ___________________________________________________________ Lab Section: ___________________ 1
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1.Consider a solution that initially contains carbonic acid (H2CO3)at 2 x 10-4mole/l and bicarbonate (HCO3-) at 2 x 10-3mole/l. (15 pts). a.What is the pH of the solution? (10 pts) H2CO3H+HCO3-2x10-40 2x10-3-x +x +x 2x10-4 - x x 2x10-3 + x 7323103.4]][[−−+=xCOHHCOH(this could be neglected-very small) 743103.4102)102)((−−−=−+xxxxxx)102(103.4102473xxxxx−=−−−8102.4−=xx37.7)102.4log(8=⇒=−pHxpH4 points for chart set-up 3 pts for correctly using Ka set-up 3 pts for correct answer b.Is this solution buffered against a pH change by the addition of a strong acid? Why or Why Not? (5 pts) Yes – this solution is buffered. If a strong acid is added the conjugate base (HCO3-) is protonated and pH is restored. An example of LeChatelier’s principle. 2 pts for correct answer of ‘Yes’ and 3 pts for reason 2.An El Nino event can be described as a disruption of the Walker Circulation in the region of the equatorial Pacific Ocean. Draw a diagram of the Walker Circulation and be sure to indicate wind directions, areas of precipitation, and at least relative temperatures and pressures. (10 pts) 2