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? 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
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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 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? 8. Which of the following uses magnetic confinement as a means to achieve the plasma density required to achieve nuclear fusion?
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