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Chemical Engineering Board Exam > DAY 2 - ARC CheCalc > Flashcards

DAY 2 - ARC CheCalc Flashcards

1
Q

Limestone (calcium carbonate) particles are stored in 50-L bags The void fraction of the particulate matter is 0.3 and the specific gravity of solid calcium carbonate is 2.93.

Estimate the bulk density of the bag contents (kg CaCO3 / liter of total volume)

a. 2.93
b. 0.88
c. 2.05
d. 1.26

A

C

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2
Q

Estimate the weight of the filled bags. Neglect the weight of the bag itself and the air in the filled bag.

a. 1500 N
b. 1000 N
c. 1200 N
d. 1300 N

A

B

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3
Q

The contents of the three bags are fed to a ball mill, a device something like a rotating clothes dryer containing steel balls. THe tumbling actions of the balls crushers the limestone particles and turns into a powder. The limestone coming out of the mill is put back into a 50 L bags. The limestone will

a. Just fill three bags
b. Fall short of filling three bags
c. Fill more than three bags
d. Fill none of the bags

A

B

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4
Q

An aqueous solution at a temperature of 70degC (158degF) contains 18 mol% KNO3 is boiled to give a final yield of solid KNO3 of 65%. The solubility of the KNO3 at 70degC is given at 20 mol%.

How much KNO3 has precipitated from the solution?

a. 15.7 mol
b. 11.7 mol
c. 10.1 mol
d. 17.1 mol

A

B

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5
Q

How much of the initial water was boiled off?

a. 58.6 mol
b. 55.6 mol
c. 56.8 mol
d. 57.8 mol

A

C

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6
Q

What is the final liquid composition?

a. 22.5 mol H2O
b. 25.2 mol H2O
c. 24.5 mol H2O
d. 57.8 mol H2O

A

B

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7
Q

An aqueous solution containing 15% NaOH and 0.5% NaCl is concentrated at a rate of 100 kg/min in an evaporator. The concentrated solution is then mixed with 2000 kg of aqueous NaOH solution in a mixer. At the end of one hour, a sample is collected from a mixer and analyzed. The analysis shows 40% NaOH and 0.8574% NaCl. Calculate the following:

The concentration of the original solution in the receiver

a. 32% NaOH
b. 25% NaOH
c. 40% NaOH
d. 56% NaOH

A

B

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8
Q

The composition of the concentrate from the evaporator

a. 60% NaOH; 2% NaCl
b. 72% NaOH ; 2% NaCl
c. 55% NaOH ; 5% NaCl
d. 48% NaOH; 5% NaCl

A

A

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9
Q

The mass of water (in kilograms) evaporated in one hour?

a. 3200 kg
b. 5100 kg
c. 4500 kg
d. 6600 kg

A

C

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10
Q

Find the preparation of potassium nitrate, 10000 kg/hr o a 20% KNO3 solution is mixed with a recycle stream and sent to an evaporator. The rate of evaporation is 1.5 times the rate of introduction of recycle stream. The concentrated solution leaving the evaporator contains 50% KNO3. This is admitted to the crystallizer which yields crystals containing 5% water. At the crystallization temperature the solubility is 50 kg/100 kg of water. The major part of the mother liquor leaving the crystallizer is returned to the crystallizer as recycle. Calculate the following:

The concentration of KNO3 in the stream entering the evaporator

a. 33%
b. 25%
c. 16%
d. 40%

A

B

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11
Q

The flow rate of recycle stream in kg/h

a. 5143
b. 4531
c. 1354
d. 3415

A

A

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12
Q

The rate of production of crystals

a. 3925
b. 2007
c. 1588
d. 4610

A

B

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13
Q

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/hr, calculate the fmass fraction of Cr in the residual liquid leaving the unit

a. 0.0154
b. 0.0027
c. 0.0301
d. 0.0078

A

B

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14
Q

What is the mass fraction of Cr in the liquid to the waste lagoon?

a. 0.0154
b. 0.0027
c. 0.0301
d. 0.0078

A

A

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15
Q

Calculate the mass fraction of Cr in the liquid to the waste lagoon if 1000 kg/hr of wastewater leaves the finishing plant.

a. 0.00154
b. 0.0027
c. 0.0301
d. 0.0078

A

B

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16
Q

Seawater contains 65 ppm of bromine in the form of bromides. In the Ethyl-Dow recovery process, 0.27 lb of 98% sulfuric acid is added per ton of water, together with the theoretical Cl2 for oxidation; finally, ethylene (C2H6) is united with the bromine to form C2H4Br2. Assuming complete recovery and using a basis of 1 lb of bromine, find the masses of 98% sulfuric acid and ethane dibromide involved.

Pound of 98% sulfuric acid

a. 1.95
b. 4.22
c. 3.39
d. 2.08

A

D

17
Q

Pound of ethane dibromide

a. 2.05
b. 1.18
c. 2.33
d. 1.97

A

B

18
Q

Solid calcium (CaF2) reacts with sulfuric acid to form solid calcium sulfate and gaseous hydrogen fluoride

A

C

19
Q

Phosphorus is precipitated with liquid alum in wastewater that contains 8 mg P/L. Based on the laboratory testing, 1.5 mole of Al will require per mole of P. The flowrate is 12000 m3/d. The formula for liquid alum is Al2(SO4)3 x 18H2O. Alum strength = 48% at a density of 1 kg/L

How much aluminum is theoretically required per unit weight of Phosphorus?

a. 1.08 kg Al/kg P
b. 0.78 kg Al/kg P
c. 0.97 kg Al/kg P
d. 0.87 kg Al/kg P

A

D

20
Q

How much alum solution is required per kg of P?

a. 36 L
b. 28 L
c. 48 L
d. 32 L

A

B

21
Q

A

A

D

22
Q

Aluminum sulfate is used in water treatment and in many chemical reaction processes. It can be made by reacting crushed bauxite (aluminum ore) with 77.0 weight percent sulfuric acid. The bauxite ore contains 55.4 weight percent aluminum oxide, the remainder being impurities. To produce crude aluminum sulfate containing 2000 lb of pure aluminum sulfate, 1080 lb of bauxite and 2510 lb of sulfuric acid solution (77.0 percent acid) are used.

Identify the excess reactant.

a. water
b. sulfuric acid
c. aluminum oxide
d. aluminum sulfate

A

B

23
Q

What percentage of the excess reactant was used?

a. 12%
b. 35%
c. 26%
d. 49%

A

A

24
Q

What was the degree of completion of the reaction?

a. 88.5%
b. 66.1%
c. 77.3%
d. 99.6%

A

D

25
Q

In a process for the manufacture of chlorine by direct oxidation of HCl with air over a catalyst to form Cl2 and H2O (only), the exit product is composed of HCl (4.4%), Cl2 (19.8%), H2O (19.8%), O2 (4%), and N2 (52%).

The limiting reactant?

a. Cl2
b. O2
c. HCl
d. N2

A

C

26
Q

The percent excess reactant?

a. 33%
b. 22%
c. 26%
d. 35%

A

C

27
Q

The degree of completion of the reaction?

a. 0.88
b. 0.9
c. 0.92
d. 0.85

A

B

28
Q

Acrylonitrile is produced in the reaction of propylene, ammonia and oxygen:

C3H6 + NH3 + 3/2 O2 = C3H3N + 3 H2O

The feed containins 10 mole % propylene, 12 mole% ammonia, and 78% air. A fractional conversion of 30% of the limiting reactant is achieved. Taking 100 mol of feed as basis, determine the following:

The perentage by which of the reactants in excess

a. 24%, 6.2%
b. 28%, 7.5%
c. 25%, 8.5%
d. 20%, 9.2%

A

D

29
Q

The mole% of water in the product gas

a. 6%
b. 7%
c. 5%
d. 9%

A

D

30
Q

Solid calcium (CaF2) reacts with sulfuric acid to form solid calcium sulfate and gaseous hydrogen fluoride. The HF is then dissolved in water to form hydrofluoric acid. A source of calcium fluoride is fluorite ore containing 96 wt% CaF2, and 4% SiO2. In a typical hydrofluoric acid manufacturing process, fluorite ore is reacted with 93 wt% aqueous sulfuric acid, supplied 15% in excess of the stoichiometric amount. Ninety-five percent of the ore dissolves in the acid. Some of the HF formed reacts with the dissolved silica in the reaction

6 HF + SiO2 (aq) -> H2SiF6 (s) + 2 H2O(l)

The hydrogen fluoride exiting from the reactor is subsequently dissolved in enough water to produce 60 wt% hydrofluoric acid. Calculate the quantity of fluorite ore needed to produce a metric ton of acid.

a. 1690 kg
b. 1530 kg
c. 1480 kg
d. 1770 kg

A

B

31
Q

Propane is dexhydrogenated to from propylene in a catalytic reactor. The process is to be designed for a 95% overall conversion of propane. The reaction products are separated into two streams: the first, which contains H2, C3H6, and 0.555% of the propane that leaves the reactor, is taken off as a product; the second stream, which contains the balance of the unreacted propane and 5% propylene in the first stream, is recycled to the reactor.

Calculate the ratio of moles recycled / mole fresh feed

a. 1.2
b. 6.8
c. 2.5
d. 9.0

A

D

32
Q

What is the single pass conversion?

a. 9.6%
b. 13.5%
c. 25.0%
d. 38.2%

A

A

33
Q

In an attempt to provide a means of generating NO cheaply, gasaeous NH is burned with 20% excess O2

4 NH3 + 5 O2 -> 4 NO + 6 H2O

The reaction is 70% complete. The NO is separated from unreacted NH3, and the latter recycled. Compute the moles of NH3 recycled per mole of NO formed.

a. 56
b. 60
c. 43
d. 38

A

C

34
Q

Thirty pounds of coal (analysis 80% C and 20% H ignoring the ash) are burned with 600 lb of air, yielding a gas having an Orsat analysis in which the ratio of CO2 to CO is 3 to 2. What is the percent excess air?

a. 20%
b. 24%
c. 22%
d. 26%

A

B

35
Q

A pure saturated hydrocarbon is burned with excess air. Orsat analysis of the products of combustion shows 9.08% CO2, 1.63% CO, 5.28% O2, and no free H2. Calculate

The formula of hydrocarbon

a. CH4
b. C2H6
c. C3H8
d. C4H10

A

C

36
Q

The percent excess air

a. 22%
b. 23%
c. 25%
d. 28%

A

C

37
Q

The dry flue gas resulting from the burning of one ton of an unknown hydrocarbon contains 8.75% CO2 and 5.53% oxygen Orsat. The combustion process uses 25% excess air and has an efficiency of 80%.

How much nitrogen is present in the flue gas?

a. 80.33
b. 93.83
c. 85.38
d. 85.33

A

D

38
Q

How many moles are in the fuel on the basis of 1000 mole of flue gas?

a. 33.7
b. 30.5
c. 23.2
d.27.3

A

C

39
Q

What is the chemical compound being burned?

a. Hexane
b. Butane
c. Propane
d. Methane

A

B

Chemical Engineering Board Exam (5 decks)

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