ECHE 311/SPRING 2015
Problem Set 2
1. What is the heat required when 12 mol of propane is heated from 250 to 1,200 oC
at approximately atmospheric pressure in a steady state-flow heat exchanger?
 Use equation 4.7 which approximate the heat capacity and calculates
ICPH.
 H  R  ICPH
 Q(n)  nH ( n is number of moles)
Answer : Q=1.942 x106 (J)
2. What is the final temperature when heat in the amount of 800 kJ is added to the 10
mol of ethylene initially at 200oC in a steady-flow heat exchanger at
approximately atmospheric pressure?
Hint :
T
 Use  
 2 (guess)
To
in equation
B
C
Q  nR{[ ATo (  1)  To2 ( 2  1)]  To3 ( 3  1)}
(1)
2
3
to estimate the best value for  and the final temperature
Answer: T=1.374 x 103 K
3. Chlorine is produced by the reaction
4HCl(g) + O2(g) = 2H2O(g) +2Cl2(g)
The feed stream to the reactor consists of 60% HCl, 36 mol% O2 and 4 mole %
N2, and it enters the reactor at 550oC. If the conversion of HCl is 75% and if the
process is isothermal, how much heat must be transferred from the reactor per
mole of the entering gas mixture?
Hint:
 Take a basis of 1 mole gas entering reactor, containing 0.6 M HCl, 0.36 M
O2 and 0.04 M N2. Therefore the amount of HCl reacted (r) is equal to
0.6x0.7=0.45.
 Using H298 as the reference, we can calculate H823 by the equation
H 823  H 298  MDCPH  R  (T  T298 )
B
C
D
MDCPH  A  ( ) T o(  1)  (
)  To2 ( 2    1) 
2
3
  To2
1
(2)
where To=298.15 K ;  
T
To
Answer: Q= -13,229 J
4. If the heat of the amount of 2,500 kJ is added to 15 mol of 1 butene initially at
260oC in a steady state-flow process at approximately atmospheric pressure, what
is its entropy change?
T
 Use  
 3 as a guess value in Eq 1 to calculate the final temperature.
To
 The entropy for 15 moles is the found by using (ICPS integral)
 S  nR  ICPS
Answer  S=1.243x106 J/K
NOT REQUIRED
5. Calculate the reversible work done on compressing 1 ft3 of mercury at a constant
temperature of 32(oF) from 1 atm to 3,000 (atm). The isothermal compressibility
of mercury at 32oF is
=3.9x10-6-0.1x10-9P
where P is in (atm) and  is in (atm)-1.

Answer: 16.65 atm ft3
6. Five kilograms of liquid carbon tetrachloride undergo a mechanically reversible,
isobaric change of state at 1 bar during which the temperature changes from 0oC to
20. Determine Vt, W, Q, Ht, and Ut. The following parameters for liquid
carbon tetrachloride at 1 bar and 0oC may be assumed independent of temperature:
=1.2x10-3 K-1, CP =0.84 kJ kg-1K-1, and
=1.590 kg m-3.

Answer:
V total = 7.638x10-5 m3
(Const P) W =-7.638 Joule
Q= 84 kJ
 H= 84 KJ
4
2
-2
Utotal  8.399  10 kgm sec
2