Practice Exams ChE - 12

1. Black Ash is treated with H2O to extract the Na2CO3 that it contains. The composition of black ash is analyzed to be :
Na2CO3 - 42%
other soluble substances - 6%
Insoluble substances - 52%

The composition of the residue is:
Na2CO3 - 4%
Insoluble solids - 85%
other soluble solids - 0.5%
H2O - 10.5%

What is the amount of Na2CO3 in the extract per 200 lb. of black ash ?
a. 791
b. ???
c. ???
d. ???

2. A composite wall consists of a 2” corkboard (inner), 6” concrete and 3” wood (outer). The thermal conductivity of the materials are 0.025, 0.8 and 0.065 Btw/ ft-hr-degF. The temperature of the inner surface of the wall is 40 degF while the outer surface of the composite wall is 78 degF. What is the temperature between cork and concrete and concrete-wood.
a. ???
b. 62, 69
c. ???
d. ???

3. A composite wall consists of W1 (outer layer) and W2 (inner layer). W1 and W2 are both 5” thick. The thermal conductivity of W1 is 1 Btw/ft-hr-degF while that of W2 is 0.1 Btw/ft-hr-degF. The temperature of the outer layer is 500 degF while that of the inner layer is 1500 degF. Find qTOTAL in Btw/hr-ft2.

4. Water flowing at 0.8 kg/sec is to be heated from 5 degC to 45 degC. If the outer surface temperature of the 2.5 cm thick pipe to which it flows is to be kept at 90 degC, what should be the length of the pipe ?
a. 1m
b. 2.1 m
c. ???
d. 2.7 m

5. The problem encountered in the use of percolation filters is:
a. channeling
b. caking
c. ???
d. ???

6. The process of using water to extract the juice from sugar cane is called
a. Salvation
b. Maceration
c. Hydrolysis
d. Liquefaction

7. Ethane is produced by reacting ethylene with hydrogen. Given the following data, find the heat of this reaction :

Heat of combustion
Ethane = -670,000
Ethylene = -600,000
Hydrogen = -120,000

a. -50,000
b. -60,000
c. 50,000
d. 60,000

8. The chemical name of Wintergreen oil is
a. benzyl acetate
b. methyl silicilate
c. linalyl acetate
d. ???

9. What is the relative humidity of air at 80 degF with a moisture content of 0.018 pounds H2O per pound of dry air ?
a. 68%
b. 82%
c. ???
d. ???

10. The advantage of packed columns over plate columns is
a. less back pressure
b. less problem with channeling
c. higher temperature
d. more contact between vapor and liquid phases

11. One of the problems encountered in permutation process is foaming. Which of the following are used to prevent foaming in fermenters?
a. ???
b. mechanical defoamers only
c. antifoaming agents only
d. mechanical defoamers and antifoaming agents