Exam #1 Thermodynamics Fall 2015 Name: ______________________________ Test booklet number 0001 Some advice: If you don’t immediately know how to solve a problem, skip it and come back to it once you’ve done all the problems that are easy for you. If you are convinced that none of the answers provided are correct, then select the answer closest to your value. You must show work for any of the calculation-based problems on the exam to get any credit. No partial credit is given on multiple choice questions.1) (1 point) The pressure of a gas in a well-sealed vertical frictionless piston-cylinder device is to be increased by adding a mass of 15 kg on the piston. If the diameter of the cylinder is 19 cm, the increase in the pressure of the gas is (a) 15.9 kPa (b) 5.2 kPa (c) 0.53 kPa (d) 0.5 Pa (e) 1.3 kPa 2) (1 point) The density and the specific volume of a simple compressible system are known. The number of additional intensive, independent properties needed to fix the state of this system is (a) 0 (b) 1 (c) 2 (d) 3 (e) 4 3) (1 point) A 3.5-kW electric resistance heater in a room is turned on and kept on for 20 min. The amount of energy transferred to the room by the heater is (a) 3.5 kJ (b) 70 kJ (c) 700 kJ (d) 4200 kJ (e) 5800 kJ4) (1 point) A rigid tank contains 7 kg of an ideal gas at 5 atm and 30C. Now a valve is opened, and half of mass of the gas is allowed to escape. If the final pressure in the tank is 1.5 atm, the final temperature in the tank is (a) -91°C (b) °18C (c) -182°C (d) 91°C (e) 15°C 5) (3 points) A 230-m3 rigid tank is filled with saturated liquid-vapor mixture of water at 120C. If 25% of the mass is liquid and 75% of the mass is vapor, the total mass in the tank is (put a box around your final answer).6) (1 point) A sealed, rigid tank contains an ideal gas. If the temperature is doubled during an adiabatic process, the pressure of the gas will (a) become halved (b) double (c) triple (d) remain constant (e) become a third 7) (1 point) A substance in a tank is at the pressure of 5.5 MPa and temperature of 260 oC. The saturation pressure at the same temperature is 4.5 MPa. What is the phase of the substance? (a) saturated mixture (b) saturated vapor (c) Saturated liquid (d) Superheated vapor (e) Compressed liquid 8) (1 point) System A and system B are in thermal equilibrium. System B and system C are in thermal equilibrium. If system A is 28 oC, which law of thermodynamics can tell us the temperature of system C? (a) 0th law (b) 1st law (c) 2nd law (d) 3rd law (e) Murphy’s law 9) (1 point) Fill in the blank: ____________ systems can have energy but not mass moving across their system boundaries. 10) (1 point) Which of the following properties best characterizes the energy absorbed as liquid water boils and turns into steam? (a) Sensible heat (b) Latent heat of vaporization (c) Specific heat (d) Latent heat of fusion (e) boiling heat 11) (1 point) A cup of hot coffee left on the table eventually cools, but a cup of cold coffee never gets hot by itself. This phenomenon can be explained by the: (a) Second law of Thermodynamics (b) Conservation of energy principle (c) Ideal gas equation (d) First law of Thermodynamics (e) Zeroth law of Thermodynamics12) (1 point) A 200 W vacuum cleaner is powered by an electric motor whose efficiency is 70%. (Note that the electric motor delivers 200 W of net mechanical power to the fan of the cleaner). The rate at which this vacuum cleaner supplies energy to the room when running is (a) 140 W (b) 200 W (c) 286 W (d) 60 W (e) 667 W 13) (2 points) Draw the saturation dome on a T-V diagram and then draw the following states, clearly indicating the path between each state State 1: 20 C water at 1 atm Heated at a constant pressure to State 2: 80 C water at 1 atm Heated at a constant pressure until all of the liquid is vaporized State 3: ~100 C water in vapor form at 1 atm Heated at a constant pressure to State 4: 130 C water at 1 atm14) (4 points) A piston cylinder device (where the piston is free to move) initially contains 12.2 kg of steam at 1150 kPa and 305 C. The cylinder loses heat to the surroundings until 80% of the mass has condensed. What is the change in volume of the