answer key final exam Version A 3-20-07

answer key final exam Version A 3-20-07 - Final Exam Chem...

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1 Final Exam - Chem 1B - Version A 3-23-07 1. 1.00 L of Helium gas is placed in a closed container that is insulated to prevent heat exchange. The container is fitted with a piston to allow the pressure to be changed. The initial pressure of the gas is 2.00 atm and it is initially at a temperature of 298 K. The pressure of the gas is then reduced in 100 small steps until a final pressure of 1.00 atm is reached. The internal energy ( E), work (w) and heat (q) changes for this process are a) E negative, w negative, and q positive b) E no change, w negative, and q positive c) E positive, w negative and q no change d) E no change, w positive, and q negative e) None of the above answer 2. On pathway I between an initial state and final state, a system absorbs 100 J of heat and the internal energy change, E is 20 J. Along pathway II between the same states, the system absorbs 50 J of heat. What is the value of the work, w, on pathway II? a) +30 J b) - 30 J answer c) - 80 J d) -70 J e) none of the above 3. When a gas is heated at constant volume from an initial temperature of 25 o C to 50 o C it absorbs 80.0 J of heat. When the same gas is heated from 25 o C to 50 o C at constant pressure, it absorbs 133 J of heat. What is the value of the enthalpy change, Δ H, when the gas is heated from 25 o to 50 o at constant volume? a) + 80.0 J b) - 80.0 J c) +133 J answer d) -133 J e) none of the above 4. A gas is compressed in one step at constant temperature from an initial volume of 20.0 L and pressure of 1.00 atm to a final pressure of 2.00 atm. The value of Δ E for this process is a) + 20 L atm b) -20 L atm c) + 10 L atm d) – 10 L atm e) none of the above answer
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2 5. When heat is added to a teapot of water at 100 0 C and 1.00 atm it boils and forms water vapor at 100 0 C. The work for this process is a) Equal to q b) Equal to minus q c) Positive d) Negative answer e) Zero 6. The enthalpy of formation of H 2 O (g) is –242 kJ/mol. What is the value of the heat, q, when 4.00 mol of H 2 (g) reacts with 1.00 mol of O 2 (g) to form H 2 O (g) at 298 K and a constant pressure of 1.00 atm? a) –242 kJ b) -986 kJ c) –484 kJ answer d) -726 kJ e) none of the above 7. Which of the following substances has a Δ H f 0 value equal to zero? a) N 2 ( l ) b) Zn ( g ) c) H 2 ( s ) d) C (diamond) e) None of the above answer 8. Which of the following uses magnetic confinement as a means to achieve the plasma density required to achieve nuclear fusion? a) Tokamak at the ITER project Answer b) Lasers at the National Ignition Facility c) Cyclotron at Lawrence Berkeley Labs d) Dark matter detection system in Minnesota e) Sun in our solar system 9. The source of heat released when uranium-238 undergoes natural radioactive decay is a) conversion of electron binding energy to the nucleus into heat b) conversion of protons into energy c) conversion of neutrons into energy d) conversion of internal energy into heat answer e) all of the above
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3 10.
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This note was uploaded on 08/06/2008 for the course CHEM 1B taught by Professor Watts during the Winter '08 term at UCSB.

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answer key final exam Version A 3-20-07 - Final Exam Chem...

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