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Chemistry 453 Winter Quarter 2013 Midterm Examination will ..., Exams of Chemistry

Carnegie InstituteChemistry

Midterm Examination will be held on Friday , 8 February. • If you are enrolled in Chemistry 453A you take the midterm from 1030-1120 in. Bagley 260.

Typology: Exams

2022/2023

Uploaded on 05/11/2023

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University of Washington
Department of Chemistry
Chemistry 453
Winter Quarter 2013
Midterm Examination will be held on Friday , 8 February
• If you are enrolled in Chemistry 453A you take the midterm from 1030-1120 in
Bagley 260
• If you are enrolled in Chemistry 453B you take the midterm from 830-920 in
Bagley 260
• Chem 453A section students cannot take the exam during the B section and vice
versa.
• After you have finished the exam, turn in your bluebook with the blank exam
inserted into the bluebook.
• Exam format will be identical to posted 2010 Midterm exam
• Covering:
• Text Sections: Ch. 22-23. Red Chapter 22 sections on binding equilibria
• Lectures 1-12
• All Problems in Homework Assignments 1-4
• Bring
• Calculator (any type, but lap top computers are not allowed)
• Pencil/Pen
• Blue/Green Book
• 1 page of notes (double-sided, see below)
• Straight edge or ruler
• Format:
• Closed Book.
• Open Notes.
• One page permitted, 8.5 inches by 11 inches, double-sided,
• You may write, Xerox, scan, etc. anything on the two sides of this page that
you wish.
• If you put a lot of effort into preparing these notes, keep track of them. You
can use them at the final exam.
• Grading: Grading of the examination will be based on the standards stated in the
Chemistry 453 course syllabus. Please review the standards section of the syllabus.
Important points to keep in mind:
• Partial credit is USUALLY given in units of 3-5 points.
• Obtaining the correct numerical answer is counted in partial credit grading.
An answer that is within 10% of the correct answer will be fully credited.
• Calculations must include physical units and a proper dimensional analysis
must be included in the calculation.
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University of Washington

Department of Chemistry

Chemistry 453

Winter Quarter 2013

Midterm Examination will be held on Friday , 8 February

  • If you are enrolled in Chemistry 453A you take the midterm from 1030-1120 in Bagley 260
  • If you are enrolled in Chemistry 453B you take the midterm from 830-920 in Bagley 260
  • Chem 453A section students cannot take the exam during the B section and vice versa.
  • After you have finished the exam, turn in your bluebook with the blank exam inserted into the bluebook.
  • Exam format will be identical to posted 2010 Midterm exam
  • Covering:
  • Text Sections: Ch. 22-23. Red Chapter 22 sections on binding equilibria
  • Lectures 1-
  • All Problems in Homework Assignments 1-
  • Bring
  • Calculator (any type, but lap top computers are not allowed)
  • Pencil/Pen
  • Blue/Green Book
  • 1 page of notes (double-sided, see below)
  • Straight edge or ruler
  • Format:
  • Closed Book.
  • Open Notes.
  • One page permitted, 8.5 inches by 11 inches, double-sided,
  • You may write, Xerox, scan, etc. anything on the two sides of this page that you wish.
  • If you put a lot of effort into preparing these notes, keep track of them. You can use them at the final exam.
  • Grading: Grading of the examination will be based on the standards stated in the Chemistry 453 course syllabus. Please review the standards section of the syllabus. Important points to keep in mind:
  • Partial credit is USUALLY given in units of 3-5 points.
  • Obtaining the correct numerical answer is counted in partial credit grading. An answer that is within 10% of the correct answer will be fully credited.
  • Calculations must include physical units and a proper dimensional analysis must be included in the calculation.
  • Students are expected to understand how to use their calculators properly. Students will NOT be forgiven for mistakes resulting from calculator errors.
  • When you are asked to explain an answer or are asked to define a term, carefully worded complete sentences are required.
  • If you are given the option to choose from a list of problems (e.g. answer three of the following five questions) you will NOT be credited for answering more than the requested number. For example, if you are allowed to select three problems out of five for answering…and you answer all five… the grader will NOT credit you for the highest three scoring problems out of five. The first three problems presented on the blue book will be graded.

B. Sample Exam

This is the format of the exam that you can expect on 8 Feb. I do not guarantee the actual midterm will be exactly this length. Some of the problems may be longer or shorter than shown here. But overall the actual midterm will be of comparable challenge.

Practice working this exam within 50 minutes. I will post the key by late Friday Feb. 1 or early Saturday Feb. 2. Do NOT simply look at the answers once they are posted and assume you can work the exam in the time allotted. The exam itself will supply physical constants. The equations you need should be on your note sheet.

Section 1( Total points=28. Answer 4 out of 6 questions).

1.1) Explain the Postulate of Equal A Priori Probabilities. What basic purpose does this postulate serve in statistical mechanics? 1.2) What is a microcaninical ensemble and how is it used in statistical mechanics? 1.3) What is the meaning of the term microstate in the context of statistical mechanics? What state function enumerates the number of microstates available to a multi-particle system? Give the equation that relates this state function to the number of microstates W. 1.4) Define the partition function Q and state how the Entropy, Internal Energy and pressure are related to Q. 1.5) Sketch a graph of the fractional helicity versus temperature for a polypeptide undergoing a non-cooperative helix-coil transition. Make the same sketch for a similar transition occurring in a fully cooperative fashion. Define cooperativity in the context of helix-coil transitions?How does cooperativity impact the partition function? 1.6) What is heat capacity from a microscopic point of view? Why does a system have a large or small heat capacity? Illustrate your answer with a two level system.

Section 2 (Total points=30. Answer three out of five problems)

2.1) The table below lists the configuration of 4 systems each composed of 10 particles distributed among 5 energy levels. Calculate the number of microstates W and the entropy for each system.

2 2

R T

R T

L K K L K K L

R T

RX TX

RX TX

′

′′

ZYZZZX

ZZZYZZXZ

ZZZYZZXZ

a) Write out the expression for the binding polynomial QB in terms of the constants L, KT, KR , and the concentration [R].

b) Calculate the average number of sites bound for L=10, KR =1, KT=0.01, and [X]=0.

c) Calculate numerical values for the ratios

[ ]

[ ]

TX

RX

and

[ ]

[ ]

2 2

TX

RX

3.2) A two state system has a ground state energy ε 0 = 0 and an excited state

with ε 1 = 3.76 × 10 −^21 J. The temperature is T=500K.

a) Evaluate the single particle partition function under these conditions.

b) Assume the number of particles in the system is 10 24. How many particles are in the ground state? How many are in the excited state?

c) Calculate the internal energy U, the entropy S, and the Helmholtz energy A. Assume the particles are distinguishable so that Q=qN.