Chemistry Worksheets - Chem 340, Fall 2013 Page 12
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19P5.33) An electrical motor is used to operate a Carnot refrigerator with an interior
temperature of 0.00°C. Liquid water at 0.00°C is placed into the refrigerator and
transformed to ice at 0.00°C. If the room temperature is 20°C, what mass of ice can be
produced in 1 min by a 0.25-hp motor that is running continuously? Assume that the
refrigerator is perfectly insulated and operates at the maximum theoretical efficiency.
We need to find the amount of heat per unit time that can be removed from the
interior of the refrigerator.
q
w
T
w
η
cold
r
t
t
T
T
t
hot
cold
273
K
1 -
1 -
0.25
hp
746
W
hp
2546
s J
293
K
273
K
The number of grams of ice that can be frozen in one minute by this amount of heat
is:
-1
q
t /
2546
s J
1 -
1 -
2
1 -
t
M
60
s
min
18
.
02
g
mol
4.5
10
g
min
ice
1 -
H
6008
J
mol
fusion
Extras :
Atkins
Exercises:
3.4(b) A sample consisting of 2.00 mol of diatomic perfect gas molecules at 250 K is compressed
−1
reversibly and adiabatically until its temperature reaches 300 K. Given that C
= 27.5 J K
V,m
−1
, calculate q, w, ΔU, ΔH, and ΔS. –
mol
note: this is an unusual C
looks like C
, but do problem
V
P
as written anyway
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