360 Chemistry Spring 2008 Dr. Jean M. Standard February 13, 2008
Name ______________________________
Exam 1 100 points
R = 0.08206 L atm mol1 K1 = 8.314 J mol1 K1 = 0.08314 L bar mol1 K1
1 atm = 101325 Pa = 1.013 bar = 760 torr; 1 bar = 105 Pa = 0.98692 atm 1 L atm = 101.3 J; 1 L bar = 100 J
1 . ) (15 points) Sketch a plot illustrating the typical behavior of the compressibility factor Z (y-axis) versus P (x-axis) for a real gas. Make sure that you indicate the ideal gas value. Briefly explain the physical reasons for the regions of positive and negative deviations from ideality.
2 2.) (14 points) a.) One mole of helium gas at 100C and 1.5 bar is expanded isothermally against a constant external pressure of 0.25 bar. Calculate w, q, and U for the expansion, assuming ideal behavior. Express your answers in units of Joules.
b.) Determine w, q, and U when one mole of helium gas at 100C and 1.5 bar is expanded reversibly and isothermally to a final pressure of 0.25 bar. Assume that the gas behaves ideally. Express your answers in units of Joules.
3 3.) (14 points) Determine whether or not the following quantities correspond to exact differentials. 3 a.) df = 2xy 2 dx + 2x 2 y dy y
b.) dP =
RT dT + R ln(V ) dV V
4 4.) (15 points) True/false, short answer, multiple choice. a . ) True or False: An ideal gas exhibits critical behavior.
b . ) True or False: The work by done stretching a rubber band is given by dw = FdL , where F is the tension of the rubber band and L is the length of the rubber band. c . ) Short answer ____________ is a state function that corresponds to the heat absorbed/released at constant pressure, q p .
____________ is a state function that corresponds to the heat absorbed/released at constant volume, qv .
d.) Multiple Choice: Circle the correct result for a constant volume (isochoric) process in which an ideal gas is heated from 100 K to 500 K. 1) 2) w 0, q = 0, U = w . w = 0, q 0, U = q.
3) w 0, q = w , U = 0. 4) w = 0, q = 0, U = 0.
5 5.) (14 points) Consider an equation of state for a gas given by Z = 1+ B , Vm
where B is a constant and Z is the compressibility factor. Starting from the definition of work, w = Pext dV , derive an expression for...