Chem eng 1

Question 1

A liquid mixture containing 45% benzene (B) and 55% toluene (T) by mass is fed to a distillation column.
A product stream leaving the top of the column (the overhead product) contains 95 mol% B, and a bottom
product stream contains 8% of the benzene fed to the column. The volumetric flowrate of the feed stream is
2000 L/hr and the specific gravity of the feed mixture is 0.872. What is the composition (mass fraction) of the
bottom product stream in terms toluene?

Answer 1

93.58%

Question 2

Paper pulp is sold on the basis that it contains 12 percent moisture; if the moisture exceeds this value, the
purchaser can deduct any charges for the excess moisture and also deduct for the freight costs of the excess
moisture. A shipment of pulp became wet and was received with a moisture content of 22 percent. If the
original price for the pulp was $40/ton of air dry pulp and if the freight is $1.00/100 lb shipped, what price
should be paid per ton of pulp delivered?

Answer 2

$53.19/ton

Question 3

Given the following analysis of the coal:
VCM -31.4%
M - 19.5%
Ash - 3.1%
Heating Value - 10100 BTU/lb
Estimate the %net H in the coal.

Answer 3

2.712%

Question 4

Blue vitriol is obtained from an evaporator-crystallizer from an aqueous solution of this salt. The fresh
feed to the process contains 30 %wt CuSO4. The wet crop contains 15 kg of the crystals per kg of saturated
solution from the crystallizer operating at 0°C. The mother liquor obtained from the crystallizer is
recycled to join the fresh feed, In the evaporator, the combined feed loses 50 % of its water content. The
evaporator has a capacity of 100 kg/sec. Solubility of CuSO4 at 0 °C is 14.3 kg in 100 kg water. Calculate
the fresh feed to recycle ratio.

Answer 4

2.786

Question 5

The furnace at the Bataan Refinery is using a fuel gas which contains methane, ethane, and 20% nitrogen.
The Orsat analysis of the combustion products showed 7.8% CO2, 7.4% O2, and 84.8%N2. The gas is burned
with excess air. The % methane in the fuel gas is

Answer 5

57.63%

Question 6

A dilute salt solution containing 6% salt is fed to an evaporator at a rate of 10000 kg/h for a trial run. Crystals
formed along with the saturated solution adhering with them are sent to a centrifuge for the recovery of the
solution. 60% of the adhering solution is recovered. It is found that the saturated solution that is withdrawn
from the evaporator is 850 kg and that is recovered by centrifuging is 200 kg. The crystals are dried to drive
off the remaining water. The dry crystals obtained weighed 360 kg. Determine the amount of water removed
in the drier.

Answer 6

513.1kg

Question 7

A fuel containing 75% ethane and 25% propane is burned with dry air. All the H2 burns to H2O and the CO2
to CO ratio is 10:1. Fifteen % excess air is supplied. Calculate m3 dry air at 280C, 765 mmHg per kgmole fuel.

Answer 7

428.09

Question 8

A medium volatile bituminous coal (mvb) has an “as received” analysis of 27.13% VCM, 62.52% FC,
7.11% ash, 0.95% S and 1.28%N. Its calorific value is 32.3 MJ/kg. This coal is burned in excess air supplied
at 30
C, 756 Torrs with 80% RH. Partial Orsat analysis of the stack gas shows 9.78% CO2 and 2.45% CO.
Calculate the % excess O2.

Answer 8

50%

Question 9

A liquid mixture contains three components A (MW = 72), B (MW = 58) and C (MW = 56) in which A
and B are present in the mole ratio 1.5:1 and the weight percent of B is 25%. A sample of the mixture is found
to contain 10 kg of C. Calculate the total number of moles of the mixture

Answer 9

557.4 moles

Question 10

A medium volatile bituminous coal (mvb) has an “as received” analysis of 27.13% VCM, 62.52% FC,
7.11% ash, 0.95% S and 1.28%N. Its calorific value is 32.3 MJ/kg. This coal is burned in excess air supplied
at 30o
C, 756 Torrs with 80% RH. Partial Orsat analysis of the stack gas shows 9.78% CO2 and 2.45% CO.
Calculate the % excess O2.

Answer 10

50%

Question 11

A liquid mixture contains three components A (MW = 72), B (MW = 58) and C (MW = 56) in which A
and B are present in the mole ratio 1.5:1 and the weight percent of B is 25%. A sample of the mixture is found
to contain 10 kg of C. Calculate the total number of moles of the mixture

Answer 11

557.4 moles

Question 12

A stream containing 5.15 wt% chromium, Cr, is contained in the wastewater from a metal finishing plant.
The wastewater stream is fed to a treatment unit that removes 95% of the chromium (no water) in the feed and
recycles it to the plant. The residual liquid stream leaving the treatment unit is sent to a waste lagoon. The
treatment unit has a maximum capacity of 4500 kg wastewater/h. If wastewater leaves the finishing plant at a
rate higher than the capacity of the treatment unit, the excess bypasses the unit and combines with residual
liquid leaving the unit, and the combined stream goes to the waste lagoon. If the wastewater leaves the finishing
plant at a rate of 6000 kg/h. Calculate the mass fraction of Cr in the residual liquid leaving the unit.

Answer 12

0.01537 kg/kg

Question 13

A solid fuel with 60% carbon and 25% nitrogen undergoes a combustion process with excess air. If the
Orsat analysis of the combustion product is 5% CO, 5% H2, 10% CO2, 10% O2 and 70% N2, how much excess
air is fed?

Answer 13

39%

Question 14

Pure ethanol vapor is fed to a reactor packed with alumina catalyst, at the rate of 100 kmole/hr. The reactor
products comprise: ethylene: 95 kmole/hr, water vapor: 97.5 k mole/hr and diethyl ether: 2.5 kmole/hr. The
reactions occurring can be represented by:
C2H5OH à C2H4 + H2O
2C2H5OH à C2H5 - O - C2H5 + H2O
The percent conversion of ethanol in the reactor is

Answer 14

100

Question 15

Pure methane is burned with 40% excess air and 25% of its carbon content is converted to CO the rest to
CO2. 90% of its hydrogen burns to water, the rest remains as unburned H2. Air supplied is at 23o
C, 758 mm
Hg with 80% RH. Calculate the percent CO2 in the Orsat analysis of the combustion products.

Answer 15

5.9%

Question 16

The solubility of NaNO3 at 40o
C and 10o
C are 51.4% by weight and 44.5% by weight, respectively. How
many grams of NaNO3 may be crystallized from a 10 kg solution initially saturated at 40o
C if the temperature
of the solution is lowered to 10o
C?

Answer 16

1243

Question 17

A fuel has the following constituents: Carbon 85%, hydrogen 13%, Oxygen 2%, When burning this fuel
in a boiler furnace the air supply is 50% in excess of the theoretical minimum required for complete
combustion, the inlet temperature of the air being 31°C and funnel temperature is 280°C. Compute its calorific
value.

Answer 17

47034.0
kj/kg

Question 18

The burning of pure ethane with dry air gives a stack gas which analyzes 9.92% CO2. The stack gases
leave at 745 mm Hg. Assuming complete combustion, determine the percent excess air.

Answer 18

29.97%

Question 19

A triple effect evaporator is fed with 1000 lb of a 5% salt solution to be concentrated to 40% solution. If
the amount of water evaporated from the first effect is 375 pounds and that from the second effect is 1.5 times
that from the third effect. Calculate the composition of salt solution leaving the second effect

Answer 19

15%

Question 20

. A gaseous fuel is composed of 20% methane, 40% ethane and 40% propane, where all percentages are by
volume. The volumetric analysis of the dry products of combustion this fuel gives 10.6% carbon dioxide, 3%
oxygen, 1% carbon monoxide and 85.4% nitrogen. Determine the air fuel ratio on a mass basis for this reaction.

Answer 20

18

Question 21

A certain coal is pulverized and burnt in a burner. Analysis of coal showed 70% C, 10.7% ash and 1.2%
N. The refuse is substantially free of combustible. A sample of the flue gas collected and analyzed in an Orsat
apparatus over mercury contains 8.3% CO2, 3.32% CO, 0.32% SO2, 3.32% H2 and 9.53% O2. Air supplied is
at 30o
C, 1 atm and saturated with water. Calculate: the % excess O2.

Answer 21

65.164%

Question 22

A gaseous fuel at 22o
C, 763 torrs and saturated with water vapor is burned with excess air. Air with 60%
RH is supplied at the same temperature and pressure as the fuel. The composition of the fuel shows 9.2% CO2,
0.4% C2H4, 20.9% CO, 15.6% H2, 1.9% CH4, and 52%N2. The stack gas leaves at 400o
C and 735 mm Hg and
contains 13.16% CO2 and 1.84% CO on a dry basis. Calculate the % excess air

Answer 22

40.18%

Question 23

A blast furnace gas analyzing 27% CO, 12% CO2, 2% H2, 5% CH4, and 54% N2 at 25o
C and 98 kPa and
saturated with water vapor is burned in 15% excess air. Air is supplied at 30o
C, 762 torrs and also saturated
with water. 90% of the total carbon in the fuel is converted to CO2, the rest to CO. Molar ratio of H2 to CO is
1:4 in the stack gas which leaves at 200o
C and 750 torrs. Calculate the % O2 in the Orsat analysis.

Answer 23

2.19%

Question 24

A solvent dewaxing unit in an oil refinery is separating 5000 bbl/day of a lubricating distillate into 23 vol
percent of slack wax and 77 vol percent of dewaxed oil. The charge is mixed with solvent, chilled, and filtered
into wax and oil solution streams. The solvent is then removed from the two streams by two banks of stripping
columns, the bottoms from each column in a bank being charged to the next column in the bank. The oil bank
consists of four columns, and the wax bank of three. A test on the charge and bottoms from each column gave
the following results:

Answer 24

37 bbl/day

Question 25

An evaporator while concentrating an aqueous solution from 10 to 40% solids evaporates 30000 kg of
water. The amount of solids handled by the system in kg is

Answer 25

4000

Question 26

A boiler is fired with coal containing 72.63%C, 14% ash, 1.6%N and 1.2%S burnt under conditions that
the elimination of combustibles from the refuse is complete. The air enters the furnace at 25C, 760 mm Hg
with 80% RH. The flue gases go to the stack at 280o
C and 110 kPa. The average flue gas Orsat analysis is
8.41% CO2, 2.52% CO, 0.76% H2 and 9.86% O2. Calculate the % excess air.

Answer 26

65.16%