ECHE 311/FALL 2005

Problem Set 2

Due Thursday September 2nd

  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.

· 

·  ( n is number of moles)

  1. 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 :

·  Use (guess)

in equation

(1)

to estimate the best value for and the final temperature

  1. 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 DH298 as the reference, we can calculate DH823 by the equation

(2)

where To=298.15 K ;

  1. 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?

·  Use as a guess value in Eq 1 to calculate the final temperature.

·  The entropy for 15 moles is the found by using (ICPS integral)

· 

  1. 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 k is in (atm)-1.

  1. 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 DVt, W, Q, DHt, and DUt. The following parameters for liquid carbon tetrachloride at 1 bar and 0oC may be assumed independent of temperature: b=1.2x10-3 K-1, CP =0.84 kJ kg-1K-1, and =1.590 kg m-3.

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