2009 Midterm2
Last name
First name
Student ID
Exam Version
A CHEM204, Winter 2009, Midterm II Instructor: Dr. G. Cosa March 19, 2009, 6.05 PM to 9.00 PM Instructions: 1. 2. 3. 4. 5.
Please write your name and student i.d. on this cover page Please write your name and student i.d on the answer sheet provided. This is a closed book examination There are 18 pages including this cover page. There are three parts to the exam; the first part (questions 1 to 20) consists of questions with multiple choices, each worth 2.5 points. Questions 21 to 25 consists of questions with multiple choices, each worth 6 points..Questions 26 to 27 are problem solving (10 points each). 6. Use your SCANTRON answer sheet to answer questions 1 to 25. 7. Answer your questions 26 to 27 directly on the exam. You are not allowed any other notes/sheets in this exam. 8. You can only use your own calculator. 9. If you write your exam problems in pencil (problems 21 to 27), you are not eligible for any regrade. 10. Show all intermediate steps used to obtain the final result. 11. When instructed to use specific constants in a calculation, follow the instructions 12. The final results MUST be accompanied of the right units and signs. Marks will be deducted when an answer has the wrong sign. Marks will be deducted when an answer has the wrong units and/or lacks the units. 13. At the end you will need to hand in the exam questions and answer sheet. 14. Formula/constants and a periodic table are provided in the last three pages of the exam. 15. You have to follow the rules and policies of McGill University Academic Integrity. 16. WARNING: The Examination Security Monitor Program detects pairs of students with unusually similar answer patterns on multiple-choice exams. Data generated by this program can be used as admissible evidence, either to initiate or corroborate an investigation or a charge of cheating under Section 16 of the Code of Student Conduct and Disciplinary Procedures
Good luck! INSTRUCTORS: please ensure that you receive both a SIGNED SCANTRON answer sheet and a SIGNED EXAM COPY from each student. Please, also prepare two separate piles, one with the SCANTRON answer sheets and one with the exams.
2nd MIDTERM EXAM, CHEM 204 Physical Chemistry for Biological Sciences March 19, 2009; Exam version A
1 of 18
First part of the exam: Short answer, multiple choice questions (20 questions, 2.5 points each question). Choose the right response to each question, and indicate the corresponding letter in the answer sheet. 1) The following plot illustrates the dependence of the Gibbs Free Energy of a reaction (ΔrG) with temperature (T). Based on the plot: ΔrG
0 0
T
A) The ΔrH Kf Kf>Kb Kb+Kf=1 The information provided is not sufficient.
11) The freezing point of water is lowered proportional to the number of solute species present. In identical experimental circumstances, if NaCl is replaced with CaCl2 as a solute in water, how will the freezing points compare? A) Tf (NaCl (aq)) < Tf (pure water) < Tf (CaCl2 (aq)) B) Tf (CaCl2 (aq)) < Tf (NaCl (aq)) < Tf (pure water) C) Tf (CaCl2 (aq)) < Tf (pure water) < Tf (NaCl (aq)) D) (NaCl (aq)) < Tf (CaCl2 (aq)) < Tf (pure water) E) (NaCl (aq)) = Tf (CaCl2 (aq)) < Tf (pure water) 12) Based on the following three plots illustrating the binding of a ligand "L" to a protein with a single binding site, where Y is the fractional saturation of sites, we can say that
A) B) C) D) E)
The ligand "L" does not bind to the protein in case A The ligand "L" has a larger association constant for the protein in case C The ligand "L" has a larger association constant for the protein in case A The ligand "L" has a larger association constant for the protein in case B. The ligand “L” does not bind to the protein in case C
2nd MIDTERM EXAM, CHEM 204 Physical Chemistry for Biological Sciences March 19, 2009; Exam version A
5 of 18
13) Given that the ionic radius for naked Li+ is 0.6 angstroms, that for naked Na+ is 0.95 angstroms and that for naked K+ is 1.33 angstroms, and considering that naked Cl- ionic radius is 1.81 angstroms, we can say that the equivalent conductance at infinite dilution Λo for the following salts in water is: A) Λo KCl > Λo NaCl > Λo LiCl B) Λo LiCl > Λo NaCl > Λo KCl C) Λo LiCl = Λo NaCl = Λo KCl D) Λo NaCl > Λo LiCl > Λo KCl E) Λo NaCl > Λo KCl > Λo LiCl 14) The extent of reaction in equilibrium is a compromise between (please choose the most appropriate answer): A) Temperature and pressure. B) Volume and internal energy C) All of the above are correct D) Conversion from reactants to products and mixing of reactants and products. E) None of the above is correct 15) Consider the following ethanol solutions with the same molar fraction of solute (x=0.05). Which solution deviates most from the ideal solution? (Or which activity coefficient, γ, deviates most from 1?) A) Benzene e B) glucose C) HCl D) H2SO4 E) methanol 16) Knowing that pure toluene vapor pressure is 0.39 atm at 80 C, and that pure benzene vapor pressure is 1 atm at the same temperature, and also knowing that they both form an ideal solution when mixed in all proportions: A) The vapor pressure of the solution will be higher the higher the concentration of benzene in the solution. B) The vapor pressure of the solution will be lower the higher the concentration of benzene in the solution. C) The vapor pressure of the solution will be the same regardless the concentration of benzene in the solution. D) ΔH > 0 for the mixing reaction of toluene with benzene. E) ΔH < 0 for the mixing reaction of toluene with benzene.
2nd MIDTERM EXAM, CHEM 204 Physical Chemistry for Biological Sciences March 19, 2009; Exam version A
6 of 18
17) The osmotic pressure pushing water up from the roots to the treetop of a redwood (105 m tall) is 10.2 atm at 298 K. If this osmotic pressure arises due to NaCl in the leaves at the treetop, the NaCl concentration in the leaves has to be: A) 0.834 M B) 0.417 M C) 0.208 M D) 0.104 M E) 10.2 M 18) Please choose the right statement based on the figures A, B and C on the right: A) Based on the plots, we cannot state whereas the enthalpy of reaction is positive, negative or zero. B) Based on the plots, the UrHo>0 in A, . UrHo0 in A, . UrSo
First name
Student ID
Exam Version
A CHEM204, Winter 2009, Midterm II Instructor: Dr. G. Cosa March 19, 2009, 6.05 PM to 9.00 PM Instructions: 1. 2. 3. 4. 5.
Please write your name and student i.d. on this cover page Please write your name and student i.d on the answer sheet provided. This is a closed book examination There are 18 pages including this cover page. There are three parts to the exam; the first part (questions 1 to 20) consists of questions with multiple choices, each worth 2.5 points. Questions 21 to 25 consists of questions with multiple choices, each worth 6 points..Questions 26 to 27 are problem solving (10 points each). 6. Use your SCANTRON answer sheet to answer questions 1 to 25. 7. Answer your questions 26 to 27 directly on the exam. You are not allowed any other notes/sheets in this exam. 8. You can only use your own calculator. 9. If you write your exam problems in pencil (problems 21 to 27), you are not eligible for any regrade. 10. Show all intermediate steps used to obtain the final result. 11. When instructed to use specific constants in a calculation, follow the instructions 12. The final results MUST be accompanied of the right units and signs. Marks will be deducted when an answer has the wrong sign. Marks will be deducted when an answer has the wrong units and/or lacks the units. 13. At the end you will need to hand in the exam questions and answer sheet. 14. Formula/constants and a periodic table are provided in the last three pages of the exam. 15. You have to follow the rules and policies of McGill University Academic Integrity. 16. WARNING: The Examination Security Monitor Program detects pairs of students with unusually similar answer patterns on multiple-choice exams. Data generated by this program can be used as admissible evidence, either to initiate or corroborate an investigation or a charge of cheating under Section 16 of the Code of Student Conduct and Disciplinary Procedures
Good luck! INSTRUCTORS: please ensure that you receive both a SIGNED SCANTRON answer sheet and a SIGNED EXAM COPY from each student. Please, also prepare two separate piles, one with the SCANTRON answer sheets and one with the exams.
2nd MIDTERM EXAM, CHEM 204 Physical Chemistry for Biological Sciences March 19, 2009; Exam version A
1 of 18
First part of the exam: Short answer, multiple choice questions (20 questions, 2.5 points each question). Choose the right response to each question, and indicate the corresponding letter in the answer sheet. 1) The following plot illustrates the dependence of the Gibbs Free Energy of a reaction (ΔrG) with temperature (T). Based on the plot: ΔrG
0 0
T
A) The ΔrH Kf Kf>Kb Kb+Kf=1 The information provided is not sufficient.
11) The freezing point of water is lowered proportional to the number of solute species present. In identical experimental circumstances, if NaCl is replaced with CaCl2 as a solute in water, how will the freezing points compare? A) Tf (NaCl (aq)) < Tf (pure water) < Tf (CaCl2 (aq)) B) Tf (CaCl2 (aq)) < Tf (NaCl (aq)) < Tf (pure water) C) Tf (CaCl2 (aq)) < Tf (pure water) < Tf (NaCl (aq)) D) (NaCl (aq)) < Tf (CaCl2 (aq)) < Tf (pure water) E) (NaCl (aq)) = Tf (CaCl2 (aq)) < Tf (pure water) 12) Based on the following three plots illustrating the binding of a ligand "L" to a protein with a single binding site, where Y is the fractional saturation of sites, we can say that
A) B) C) D) E)
The ligand "L" does not bind to the protein in case A The ligand "L" has a larger association constant for the protein in case C The ligand "L" has a larger association constant for the protein in case A The ligand "L" has a larger association constant for the protein in case B. The ligand “L” does not bind to the protein in case C
2nd MIDTERM EXAM, CHEM 204 Physical Chemistry for Biological Sciences March 19, 2009; Exam version A
5 of 18
13) Given that the ionic radius for naked Li+ is 0.6 angstroms, that for naked Na+ is 0.95 angstroms and that for naked K+ is 1.33 angstroms, and considering that naked Cl- ionic radius is 1.81 angstroms, we can say that the equivalent conductance at infinite dilution Λo for the following salts in water is: A) Λo KCl > Λo NaCl > Λo LiCl B) Λo LiCl > Λo NaCl > Λo KCl C) Λo LiCl = Λo NaCl = Λo KCl D) Λo NaCl > Λo LiCl > Λo KCl E) Λo NaCl > Λo KCl > Λo LiCl 14) The extent of reaction in equilibrium is a compromise between (please choose the most appropriate answer): A) Temperature and pressure. B) Volume and internal energy C) All of the above are correct D) Conversion from reactants to products and mixing of reactants and products. E) None of the above is correct 15) Consider the following ethanol solutions with the same molar fraction of solute (x=0.05). Which solution deviates most from the ideal solution? (Or which activity coefficient, γ, deviates most from 1?) A) Benzene e B) glucose C) HCl D) H2SO4 E) methanol 16) Knowing that pure toluene vapor pressure is 0.39 atm at 80 C, and that pure benzene vapor pressure is 1 atm at the same temperature, and also knowing that they both form an ideal solution when mixed in all proportions: A) The vapor pressure of the solution will be higher the higher the concentration of benzene in the solution. B) The vapor pressure of the solution will be lower the higher the concentration of benzene in the solution. C) The vapor pressure of the solution will be the same regardless the concentration of benzene in the solution. D) ΔH > 0 for the mixing reaction of toluene with benzene. E) ΔH < 0 for the mixing reaction of toluene with benzene.
2nd MIDTERM EXAM, CHEM 204 Physical Chemistry for Biological Sciences March 19, 2009; Exam version A
6 of 18
17) The osmotic pressure pushing water up from the roots to the treetop of a redwood (105 m tall) is 10.2 atm at 298 K. If this osmotic pressure arises due to NaCl in the leaves at the treetop, the NaCl concentration in the leaves has to be: A) 0.834 M B) 0.417 M C) 0.208 M D) 0.104 M E) 10.2 M 18) Please choose the right statement based on the figures A, B and C on the right: A) Based on the plots, we cannot state whereas the enthalpy of reaction is positive, negative or zero. B) Based on the plots, the UrHo>0 in A, . UrHo0 in A, . UrSo
