2010 Winter Midterm 2
Last name
First name
Student ID
Exam Version
A CHEM204, Winter 2010, Midterm II Instructor: Dr. G. Cosa March 17, 2010, 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 16 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 3 points. Questions 21 to 25 are problem solving (6 points each), question 26 is worth 10 points. 6. Use your SCANTRON answer sheet to answer questions 1 to 20. Questions 21-26, answers in exam 7. You can only use your own calculator. 8. If you write your exam problems in pencil (problems 21 and onwards), you are not eligible for any regrade. 9. Show all intermediate steps used to obtain the final result. 10. When instructed to use specific constants in a calculation, follow the instructions 11. 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. 12. At the end you will need to hand in the exam questions and answer sheet. 13. Formula/constants and a periodic table are provided in the last three pages of the exam. 14. You have to follow the rules and policies of McGill University Academic Integrity. 15. 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 17, 2010; Exam version A
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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)
Based on the following figure obtained at pressure P, where the S trace represents the molar Gibbs free energy for the solid, the L line represents the molar Gibbs free energy for the liquid, and the G line represents the molar Gibbs free energy for the gas.
A) B) C) D) E)
The solid and gas exist in equilibrium at a temperature Ts-l. The liquid and solid exist in equilibrium at a temperature Ts-l. The liquid and gas exist in equilibrium at a temperature Tl-g. All three phases exist at equilibrium in the shaded region where the three lines intersect. The liquid is never in equilibrium with either the solid or gas at this pressure P, regardless the temperature.
2) When ammonium nitrate is dissolved in water, the solution becomes colder, we can safely say based on this information that: A) The ΔrH 0, ΔrG >0 and ΔrS 0, ΔrG 0. D) The ΔrH >0, ΔrG >0 and ΔrS >0. E) All of the above are wrong. 3) A solution of toluene and benzene behaves ideally. Calculate the chemical potential of benzene in toluene relative to that pure benzene, when benzene mole fraction is 0.4 at 25 oC. A) μbenzene- μbenzene* = -2.27 kJ B) μbenzene- μbenzene* = -4.54 kJ C) μbenzene- μbenzene* = +2.27 kJ D) μbenzene- μbenzene* = +9.081 kJ E) All of the above are wrong. 4) In a non ideal solution of an electrolyte (NaCl), the electrolyte activity coefficient decreases with (please mark the right answer): A) Further dilution with pure solvent B) Increasing solvent dielectric constant C) Decreasing ionic strength D) Addition of an inert electrolyte E) None of the above 2nd MIDTERM EXAM, CHEM 204 Physical Chemistry for Biological Sciences March 17, 2010; Exam version A
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5) The following figure shows the phase diagrams for two species. The diagrams are superimposed to assist in their comparison. Based on the phase diagrams, where trace 1 corresponds to compound "1" and trace 2 corresponds to compound "2" it is true that:
A) B) C) D)
In 2 but not 1 boiling temperature decrease as the external pressure increase In 1 but not 2 melting temperature decrease as the external pressure increase The enthalpy of melting for solid 1 and for solid 2 is negative The molar volume of solid 1 is smaller than that of liquid 1, and the molar volume of solid 2 is larger than that of liquid 2 E) All of the above are wrong
6)
Given the following plot for the molar Gibbs energy vs. P for a pure substance at constant T, one of the statements below regarding states 1, 2 and 3 is correct. 1
2 3 A) The molar Gibbs free energy is the same for states 1, 2 and 3. B) The molar volume of state 1 is larger than that of state 3, which is in turn larger than that of state 2. C) The molar volume of state1 is smaller than that of state 2, which is in turn smaller than that of state 3. D) The absolute entropy of state 1 is smaller than that of state 2, which is in turn smaller than that of state 3. E) None of the above is correct. 7)
The ΔHsolvation of NaCl in water is -775 kJ/mol; the ΔHsolvation of NaBr in water is -751 kJ/mol. From this data, it is safe to conclude that. A) The solvation energy of Br- is the same as the solvation energy of Cl-. B) The lattice energy is the same for both salts. C) Solvation is an endothermic process for both salts. D) The size of Br- > size Cl-. E) None of the above is correct.
2nd MIDTERM EXAM, CHEM 204 Physical Chemistry for Biological Sciences March 17, 2010; Exam version A
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8)
A process at constant T and P, for which the state functions of the system fulfill: ΔH > 0 and ΔS > 0: A) Will not occur spontaneously, regardless of the temperature. B) Will be spontaneous only ate very low temperatures, but not at high temperatures. C) Will be spontaneous at all temperatures. D) Will be spontaneous only at very high temperatures, but not at low temperatures. E) None of the above is correct
9)
The Gibbs energy is a criterion of spontaneity A) When entropy can not be used B) At constant T and P C) At constant n (number of moles) D) At constant T and V E) All of the above are wrong
10) One of the following statements on the thermodynamics of mixing for two ideal gases at the same initial T and P is correct, please mark it: A) The enthalpy of mixing reaches a minimum when the two gases are in equimolar concentrations. B) The Gibbs free energy change for mixing two ideal gases is positive. C) Mixing is spontaneous. D) The entropy change for mixing two ideal gases is zero. E) All of the above are wrong. 11) Ions of opposite charge in media of higher dielectric constant than ethanol will be: A) More associated than in ethanol. B) Equally associated in ethanol and in the media of higher dielectric constant. C) Less associated than in ethanol. D) They do not interact. E) All of the above are right. 12) Given the following values of Λ0 (equivalent conductance at infinite dilution) for LiCl = 115.03 Ω−1equiv-1cm2 and KCl = 150.03 Ω−1equiv-1cm2. A) The magnitude of the difference of the equivalent conductance at infinite dilution for KNO3 and LiNO3 will be 70 Ω−1equiv-1cm2. B) We can not tell the magnitude of the difference of the equivalent conductance at infinite dilution for KNO3 and LiNO3 since we do not have enough information. C) The magnitude of the difference of the equivalent conductances at infinite dilution for KNO3 and LiNO3 will be 35 Ω−1equiv-1cm2. D) The magnitude of the difference of the equivalent conductance at infinite dilution for NaCl and CsCl will be the same as for LiCl and KCl. E) All of the above are wrong.
2nd MIDTERM EXAM, CHEM 204 Physical Chemistry for Biological Sciences March 17, 2010; Exam version A
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13)
Knowing that toluene vapor pressure is 0.39 atm at 80 C, and that 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) ΔH = 0 for the mixing reaction of toluene with benzene. D) Both A and B are correct. E) Both A and C are correct.
14) Which of the three plots correspond to an ideal dilute solution where the solute-solvent interactions are stronger than solute-solute or solvent-solvent interactions? A
A) B) C) D) E)
B
C
: Plot A Plot B Plot C All three plots display ideal solutions Both plots B and C, where the total vapor pressure is linearly dependent on the solute and solvent concentration at small solute concentration ranges.
15) The osmotic pressure arising from 1 mg/ml of carboxypeptidase (CPA) is 0.27 mm Hg at 300K. Based solely on this information, it is safe to say that the molecular weight of carboxypeptidase is: A) 173110 g/mol B) 17311 g/mol C) 69244 g/mol D) 34622 g/mol E) None of the above. 16) The hydration of gases of ions is always exothermic. Which of the following combinations would you expect to have the largest in magnitude (most negative) heat of hydration? A) Small ionic radius, small charge B) Large ionic radius, small charge C) Large ionic radius, large charge D) Neutral species E) Small ionic radius, large charge
2nd MIDTERM EXAM, CHEM 204 Physical Chemistry for Biological Sciences March 17, 2010; Exam version A
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17) Consider the following 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) ethanol B) Sucrose C) HCl D) H2SO4 E) FeCl3 18) Boiling occurs when the vapour pressure of a liquid equals the atmospheric pressure. In the high altitude city of Denver, is the boiling point of water A) >100 °C B) 100 °C C)
First name
Student ID
Exam Version
A CHEM204, Winter 2010, Midterm II Instructor: Dr. G. Cosa March 17, 2010, 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 16 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 3 points. Questions 21 to 25 are problem solving (6 points each), question 26 is worth 10 points. 6. Use your SCANTRON answer sheet to answer questions 1 to 20. Questions 21-26, answers in exam 7. You can only use your own calculator. 8. If you write your exam problems in pencil (problems 21 and onwards), you are not eligible for any regrade. 9. Show all intermediate steps used to obtain the final result. 10. When instructed to use specific constants in a calculation, follow the instructions 11. 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. 12. At the end you will need to hand in the exam questions and answer sheet. 13. Formula/constants and a periodic table are provided in the last three pages of the exam. 14. You have to follow the rules and policies of McGill University Academic Integrity. 15. 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 17, 2010; Exam version A
1 of 16
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)
Based on the following figure obtained at pressure P, where the S trace represents the molar Gibbs free energy for the solid, the L line represents the molar Gibbs free energy for the liquid, and the G line represents the molar Gibbs free energy for the gas.
A) B) C) D) E)
The solid and gas exist in equilibrium at a temperature Ts-l. The liquid and solid exist in equilibrium at a temperature Ts-l. The liquid and gas exist in equilibrium at a temperature Tl-g. All three phases exist at equilibrium in the shaded region where the three lines intersect. The liquid is never in equilibrium with either the solid or gas at this pressure P, regardless the temperature.
2) When ammonium nitrate is dissolved in water, the solution becomes colder, we can safely say based on this information that: A) The ΔrH 0, ΔrG >0 and ΔrS 0, ΔrG 0. D) The ΔrH >0, ΔrG >0 and ΔrS >0. E) All of the above are wrong. 3) A solution of toluene and benzene behaves ideally. Calculate the chemical potential of benzene in toluene relative to that pure benzene, when benzene mole fraction is 0.4 at 25 oC. A) μbenzene- μbenzene* = -2.27 kJ B) μbenzene- μbenzene* = -4.54 kJ C) μbenzene- μbenzene* = +2.27 kJ D) μbenzene- μbenzene* = +9.081 kJ E) All of the above are wrong. 4) In a non ideal solution of an electrolyte (NaCl), the electrolyte activity coefficient decreases with (please mark the right answer): A) Further dilution with pure solvent B) Increasing solvent dielectric constant C) Decreasing ionic strength D) Addition of an inert electrolyte E) None of the above 2nd MIDTERM EXAM, CHEM 204 Physical Chemistry for Biological Sciences March 17, 2010; Exam version A
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5) The following figure shows the phase diagrams for two species. The diagrams are superimposed to assist in their comparison. Based on the phase diagrams, where trace 1 corresponds to compound "1" and trace 2 corresponds to compound "2" it is true that:
A) B) C) D)
In 2 but not 1 boiling temperature decrease as the external pressure increase In 1 but not 2 melting temperature decrease as the external pressure increase The enthalpy of melting for solid 1 and for solid 2 is negative The molar volume of solid 1 is smaller than that of liquid 1, and the molar volume of solid 2 is larger than that of liquid 2 E) All of the above are wrong
6)
Given the following plot for the molar Gibbs energy vs. P for a pure substance at constant T, one of the statements below regarding states 1, 2 and 3 is correct. 1
2 3 A) The molar Gibbs free energy is the same for states 1, 2 and 3. B) The molar volume of state 1 is larger than that of state 3, which is in turn larger than that of state 2. C) The molar volume of state1 is smaller than that of state 2, which is in turn smaller than that of state 3. D) The absolute entropy of state 1 is smaller than that of state 2, which is in turn smaller than that of state 3. E) None of the above is correct. 7)
The ΔHsolvation of NaCl in water is -775 kJ/mol; the ΔHsolvation of NaBr in water is -751 kJ/mol. From this data, it is safe to conclude that. A) The solvation energy of Br- is the same as the solvation energy of Cl-. B) The lattice energy is the same for both salts. C) Solvation is an endothermic process for both salts. D) The size of Br- > size Cl-. E) None of the above is correct.
2nd MIDTERM EXAM, CHEM 204 Physical Chemistry for Biological Sciences March 17, 2010; Exam version A
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8)
A process at constant T and P, for which the state functions of the system fulfill: ΔH > 0 and ΔS > 0: A) Will not occur spontaneously, regardless of the temperature. B) Will be spontaneous only ate very low temperatures, but not at high temperatures. C) Will be spontaneous at all temperatures. D) Will be spontaneous only at very high temperatures, but not at low temperatures. E) None of the above is correct
9)
The Gibbs energy is a criterion of spontaneity A) When entropy can not be used B) At constant T and P C) At constant n (number of moles) D) At constant T and V E) All of the above are wrong
10) One of the following statements on the thermodynamics of mixing for two ideal gases at the same initial T and P is correct, please mark it: A) The enthalpy of mixing reaches a minimum when the two gases are in equimolar concentrations. B) The Gibbs free energy change for mixing two ideal gases is positive. C) Mixing is spontaneous. D) The entropy change for mixing two ideal gases is zero. E) All of the above are wrong. 11) Ions of opposite charge in media of higher dielectric constant than ethanol will be: A) More associated than in ethanol. B) Equally associated in ethanol and in the media of higher dielectric constant. C) Less associated than in ethanol. D) They do not interact. E) All of the above are right. 12) Given the following values of Λ0 (equivalent conductance at infinite dilution) for LiCl = 115.03 Ω−1equiv-1cm2 and KCl = 150.03 Ω−1equiv-1cm2. A) The magnitude of the difference of the equivalent conductance at infinite dilution for KNO3 and LiNO3 will be 70 Ω−1equiv-1cm2. B) We can not tell the magnitude of the difference of the equivalent conductance at infinite dilution for KNO3 and LiNO3 since we do not have enough information. C) The magnitude of the difference of the equivalent conductances at infinite dilution for KNO3 and LiNO3 will be 35 Ω−1equiv-1cm2. D) The magnitude of the difference of the equivalent conductance at infinite dilution for NaCl and CsCl will be the same as for LiCl and KCl. E) All of the above are wrong.
2nd MIDTERM EXAM, CHEM 204 Physical Chemistry for Biological Sciences March 17, 2010; Exam version A
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13)
Knowing that toluene vapor pressure is 0.39 atm at 80 C, and that 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) ΔH = 0 for the mixing reaction of toluene with benzene. D) Both A and B are correct. E) Both A and C are correct.
14) Which of the three plots correspond to an ideal dilute solution where the solute-solvent interactions are stronger than solute-solute or solvent-solvent interactions? A
A) B) C) D) E)
B
C
: Plot A Plot B Plot C All three plots display ideal solutions Both plots B and C, where the total vapor pressure is linearly dependent on the solute and solvent concentration at small solute concentration ranges.
15) The osmotic pressure arising from 1 mg/ml of carboxypeptidase (CPA) is 0.27 mm Hg at 300K. Based solely on this information, it is safe to say that the molecular weight of carboxypeptidase is: A) 173110 g/mol B) 17311 g/mol C) 69244 g/mol D) 34622 g/mol E) None of the above. 16) The hydration of gases of ions is always exothermic. Which of the following combinations would you expect to have the largest in magnitude (most negative) heat of hydration? A) Small ionic radius, small charge B) Large ionic radius, small charge C) Large ionic radius, large charge D) Neutral species E) Small ionic radius, large charge
2nd MIDTERM EXAM, CHEM 204 Physical Chemistry for Biological Sciences March 17, 2010; Exam version A
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17) Consider the following 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) ethanol B) Sucrose C) HCl D) H2SO4 E) FeCl3 18) Boiling occurs when the vapour pressure of a liquid equals the atmospheric pressure. In the high altitude city of Denver, is the boiling point of water A) >100 °C B) 100 °C C)
