1.11.7
The solutions for these problems are the solutions for problems 1.11.7 in the 2
nd
edition Solutions Manual
.
1.8
The washing machine is a batch reactor in which a first order decay of grease on the
clothes is occurring.
The integrated form of the mass balance equation is:
kt
C
C

0
e
=
First, find
k
:
1

0
0
0
min
0.128
0.88
1
ln
min
1
1
0.88
ln
min
1
1
ln
1
=
=
=
=
C
C
C
C
t
k
Next, calculate the grease remaining on the clothes after 5 minutes:
(
)
(
)(
)
g
0.264
e
g
0.500
e
1
1
min
.00
5
min
128
.
0


0
=
=
=
kt
m
m
The grease that is not on the clothes must be in the water, so
g/L
0.00472
L
50.0
g
0.264

g
0.500
w
=
=
C
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