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Exam 2 for Elementary Quantitative Analysis | CHEM 221, Exams of Chemistry

University of Nebraska–Lincoln (UNL)Chemistry

Material Type: Exam; Class: Elementary Quantitative Analysis; Subject: Chemistry ; University: University of Nebraska - Lincoln; Term: Fall 2006;

Typology: Exams

Pre 2010

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CHEMISTRY 221 - Dr. Powers Second Exam - FALL 2006
PRINT NAME ______________________________________________
(Last) (First) (MI)
ID# ___________________________
Signature ________________________________________
SECOND EXAM Lab Section______
October 26, 2006
BE SURE YOU HAVE 12 DIFFERENT PAGES OF THIS EXAM
**********WRITE YOUR NAME ON EVERY PAGE****************
SHOW ALL WORK - NO WORK - NO CREDIT
REPORT ALL ANSWERS WITH CORRECT LABELS AND SIGNIFICANT FIGURES
• All Cell phones must be turned off and cannot be used as a calculator.
• You may use a calculator, and an exam data sheet.
• Raise your hand if you have a question.
• Keep your eyes on your own paper.
• Several exam forms may be in use. It is a code violation if data from another exam form appears
on your paper.
• Keep all REQUIRED exams as part of your records.
REQUEST FOR REGRADE _______________Date
EXAMS SUBMITTED FOR REGRADES SHOULD NOT LEAVE THE RESOURCE CENTER!
Please regrade question because___________________________________________
_________________________________________________________________________
_________________________________________________________________________
Please regrade question because __________________________________________
_________________________________________________________________________
_________________________________________________________________________
Please regrade question because __________________________________________
_________________________________________________________________________
______ Check here if there is a mistake in addition.
You must sign your regrade request, or it will not be considered a valid request.
I accept responsibility for all answers contained herein. ________________________________
Signature
When submitting regrade request, do not write on exam pages. Additional questions or comments are to
be placed on a separate sheet of paper and turned in with your test. Sign these as well.
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Download Exam 2 for Elementary Quantitative Analysis | CHEM 221 and more Exams Chemistry in PDF only on Docsity!

CHEMISTRY 221 - Dr. Powers Second Exam - FALL 2006

PRINT NAME ______________________________________________

(Last) (First) (MI)

ID# ___________________________

Signature ________________________________________

SECOND EXAM Lab Section ______

October 26, 2006

BE SURE YOU HAVE 12 DIFFERENT PAGES OF THIS EXAM

**********WRITE YOUR NAME ON EVERY PAGE****************

SHOW ALL WORK - NO WORK - NO CREDIT

REPORT ALL ANSWERS WITH CORRECT LABELS AND SIGNIFICANT FIGURES

  • All Cell phones must be turned off and cannot be used as a calculator.
  • You may use a calculator, and an exam data sheet.
  • Raise your hand if you have a question.
  • Keep your eyes on your own paper.
  • Several exam forms may be in use. It is a code violation if data from another exam form appears on your paper.
  • Keep all REQUIRED exams as part of your records. REQUEST FOR REGRADE _______________Date EXAMS SUBMITTED FOR REGRADES SHOULD NOT LEAVE THE RESOURCE CENTER!

Please regrade question because___________________________________________

_________________________________________________________________________

_________________________________________________________________________

Please regrade question because __________________________________________

_________________________________________________________________________

_________________________________________________________________________

Please regrade question because __________________________________________

_________________________________________________________________________

______ Check here if there is a mistake in addition. You must sign your regrade request, or it will not be considered a valid request. I accept responsibility for all answers contained herein. ________________________________ Signature When submitting regrade request, do not write on exam pages. Additional questions or comments are to be placed on a separate sheet of paper and turned in with your test. Sign these as well.

Question No. Possible Points Points Earned TA Initials

Total 100

USEFUL EQUATIONS

Monoprotic Weak Acid: Diprotic Weak acid: Isoionic point: Triprotic Weak acid: Debye-Hϋckel Equation:ckel Equation: Gas Constant : 8.314472 J/K.mol ^    ^       (^1305) 0 51 2 ^   

. z log 2 K K^2 4 ( 1 )(F)(K ) [ H ] a^ a a     (^)  K F K K F K K H w     1 [ ]^211 K F K K F K K H w     1 [ ]^121 K F K K F K K H w     1 [ ]^211 K F K K F K K H w     2 [ ]^232

  1. (20 points) Identify which reactions are expected to proceed spontaneously and which are expected to be non-spontaneous. Please explain why. a. (8 points) Conversion of n-hexane to 2,2-dimethylbutane at room temperature (25oC)? compound Ho^ (kcal.mol) So^ (cal/mol.K) n-hexane -167 + 2,2-dimethylbutane -186 + b. (4 points) Conversion of n-hexane to 2,2-dimethylbutane during the petroleum cracking process (400oC)? c. (4 points) Ionization of acetic acid in water (Ka = 1.75x10-5)? d. (4 points) Ionization of HCl in water?
  1. (12 points) Provide an example for the following terms. Please write out a complete chemical reaction using real compounds to illustrate the concepts (do not use a general description). a. Lewis acid b. Protic Acid c. Brønsted-Lowry Base d. Base/Conjugate acid pair
  1. (32 points) What is the Hg 2 +2^ concentration when Hg 2 Cl 2 (Ksp = 1.2x10-18) is dissolved in: a. (6 points) pure water b. (8 points) 0.01 M NaOH c. (10 points) 0.01M NaCl.

solution containing both Fe3+^ and Cu2+^ was titrated with EDTA and absorbance was measured at 745 nm (red). a. (2 points) What happens at point A? b. (2 points) What happens at point B? c. (3 points) A new technician is being trained using Fe3+^ and Cu2+^ standards. He is using a calibrated buret and obtains a similar titration curve as above, but his measured concentrations are systematically high. Why? d. (3 points) Describe one method that would correct the technician’s mistake.

  1. (15 points) A solution is composed of 0.1 M acetic acid (pKa = 4.756) in H 2 O ( ignore activity coefficients ). Absorbance A

B

Acetic acid acetate a. (5 points) What is the pH of this solution? b. (5 points) What is required to make the above solution a buffer with a pH of 3.0? c. (2 points) Is this an optimal pH for this buffer?