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# 2011_09_Tests.pdf

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York University

Chemistry

CHEM 2011

Michael Mozurkewich

Winter

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CHEM 2011.03 Test #1 October 5, 2009
NAME:______________________________ STUDENT NUMBER:________________
You have 50 minutes to complete this quiz. Calculators are permitted. Other electronics, such as
cell phones and iPods, are not. Make sure theyare turned off.
There are 4 questions. There are 30 total marks.
5 3 !3 3
1.000 bar = 1.000×10 Pa 1.000 liter = 1000 cm = 1.000×10 m
!1 !1
gas constant = 8.314 J K mol 0.00° C = 273.15 K
1. An ideal gas undergoes a three step process; at the end of the process, the gas has been
returned to its original state. For each step of the process, and for the cycle as a whole,
indicate whether q, w, and )U are less than, equal to, or greater than zero by circling the
correct answer. You will be graded on the internal consistencyof your answers as well on the
individual answers.
[2] (a) The first step is an adiabatic expansion against a constant external pressure.
q < 0 q = 0 q > 0
w < 0 w = 0 w > 0
)U < 0 )U = 0 )U > 0
[2] (b) In the second step, the gas is heated at constant volume until it has been returned to its
original temperature.
q < 0 q = 0 q > 0
w < 0 w = 0 w > 0
)U < 0 )U = 0 )U > 0
[2] (c) The final step is an isothermal compression.
q < 0 q = 0 q > 0
w < 0 w = 0 w > 0
)U < 0 )U = 0 )U > 0
[1] (d) For the cycle as a whole:
)U < 0 )U = 0 )U > 0
Brief Answers:
(a) q = 0, w < 0, )U < 0 (b) q > 0, w = 0, )U > 0 (c) q < 0, w > 0, )U = 0 (d) )U = 0 CHEM 2011.03 Test #1 October 5, 2009
2. A system consists of 6.00 moles of benzene. It is initially at a temperature of 76.0°C, a
pressure of 0.878 bar, and a volume of 534.7 cm . Then 207.6 kJ of energyis added as heat,
causing the all the liquid to evaporate reversibly and form gas at the same temperature and
pressure. You may assume that the vapor behaves as an ideal gas. Be sure to state anyother
assumptions or approximations that you make.
[4] (a) Calculate the volume of the system at the end of this process.
[7] (b) Calculate q, w, )U, and )H for the system during this process.
[1] (c) Circle the correct ending: During this process, the average velocityof the benzene
molecules
increases. decreases. remains the same.
3. The definitions of isothermal compressibility and thermal expansion coefficient are given
above.
[2] (a) Treat P as a function of T and V and write out the general expression for the total
differential of P.
[3] (b) Start from the expression and derive an expression for in
terms of T, V, $, and 6 (it might be that not all of these appear in the result).
4. 5.00 moles of CO (g)2is in a rigid container with a volume of 3.00 liters. The initial
temperature is 291 K and the initial pressure is 33.3 bar. Then 4.95 kJ of energy is added to
the gas as heat; this raises the temperature to 325 K and raises the pressure to 38.3 bar.
CO (2) can NOT be treated as an ideal gas under these conditions.
[6] Calculate )U and )H for the system during this process.
Brief Answers:
2.(a) V = 0.198 m 3 (b) q = 207.6 kJ, )H = 207.6 kJ, w = !17.4 kJ, )U = 190.2 kJ (c) same
3.(a) (b)
4. )U = 4.95 kJ, )H = 6.45 kJ CHEM 2011.03 Test #2 October 30, 2009
NAME:______________________________ STUDENT NUMBER:________________
You have 50 minutes to complete this quiz. Calculators are permitted. Other electronics, such as cell
phones and iPods, are not. Make sure theyare turned off.
There are 4 questions. There are 30 total marks.
5 3 !3 3
1.000 bar = 1.000×10 Pa 1.000 liter = 1000 cm = 1.000×10 m
gas constant = 8.314 J K mol !1 0.00° C = 273.15 K
H / U + PV A / U ! TS G / H ! TS
1. For each of the following processes, indicate whether )S is positive, negative, or zero for the
system and for the universe bycircling the correct answers. Brieflyjustifyyour answers.
[4] (a) Water at 0.00°C freezes to form ice at 0.00°C. The surroundings are also at 0.00°C.
For the system: )S < 0 )S =0 )S > 0
For the universe: )S < 0 )S =0 )S > 0
[4] (b) The following exothermic reaction occurs spontaneouslyat constant temperature and
pressure:
NH N4 (s3 6 N O(g)2+ 2H O(l) 2
For the system: )S < 0 )S =0 )S > 0
For the universe: )S < 0 )S =0 )S > 0
!1

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