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CHEN 204
Fall 2010
Practice Exam 1
1. You purchase a thermocouple with markings between 0 and 100. A calibration plot for the
thermocouple is available from the manufacturer and is a straight line in logarithmic coordinates.
The line passes through the points (G
1
= 20, T
1
= 110) and (G
2
= 40, T
2
= 250), where G is the
thermocouple reading and T is the temperature in K.
(a)
Derive an equation for T (K) in terms of the thermocouple reading G.
(b)
Without doing any calculations, briefly
justify whether you will have confidence in a
temperature reading of 325K or 165K.
2.
The absolute pressure of a gas
P
is related to its volume, and temperature by the
ideal gas
equation PV
= 0.08206
nT
.
(a)
If
n
is in moles,
P
is in atm,
T
is in K, and
V
is in L, what are the units of 0.08206?
(b)
In an experiment, you measure the pressure of a gas mixture using a Bourdon gauge
. If
the tank volume
V
is in ft
3
, the temperature
T
is in
o
F, and
n
is in lbmoles, express the
ideal gas equation of state in terms of the new units.
(c)
A gas mixture containing 65 mole% O
2
and 35 mole% CO
2
is stored in a 3.5 ft
3
tank.
The tank contents are at 95
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 Fall '08
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