Solved Problems in Chem & Che - Questions 2012

Basic Chemistry & Elementary Chemical Engineering Review Questions 1. It is composed of two or more elements which can be broken down into simpler substances by chemical means. A. Element

B. Heterogeneous Mixture

C. Compound

D. Homogenous Mixture

2. It is a physical change of gas to solid. A. Deposition

B. Sublimation C. Evaporation D. Melting

3. It is the ratio of the density of a substance to water (4°C) or to air (20°C, 1 atm). A. Specific Weight

B. Density

C. Specific Volume

D. Specific Gravity

4. A container has a mass of 78.91 g when empty and 92.44 g when filled with water. The density of water is 1.0 g/cm3. What is the volume of the container? A. 78.91 cc

B. 13.53 cc

C. 92.44 cc

D. 1.0 cc

5. It is the smallest particle of an element or compound that can have a stable independent existence. A. Atom

B. Molecule

C. Neutron

D. Electron

6. What is the mass in grams of 10 million SO2 molecules? S = 32 g/mol ; O = 16 g/mol A. 8.0 x10-16

B. 64x107

C. 5.3x10-16

D. 1.1x10-15

7. It is the sum of the atomic weights of the elements in the formula, each taken the number of times the element occurs. It is usually named for weights of ionic compounds. A. Specific weight

B. AMU

C. Formula Weight

D. Empirical Formula

8. What is the %O by mass of 5.0 grams of H2O? H = 1 g/mol ; O = 16 g/mol A. 5.56

B. 88.90

C. 11.11

D. 75.30

9. A 20.882-g sample of an ionic compound is found to contain 6.072g of Na, 8.474g of S, and 6.336g of O. What is its simplest formula? Na = 23.0 ; S = 32.0 ; O = 16 A. Na2S2O3

B. Na2SO3

C. NaSO

D. Na3S2O2

10. A 0.1014-g sample of purified glucose was burned in a C-H combustion train to produce 0.1486 g of CO2 and 0.0609 g of H2O. An elemental analysis showed that glucose contains only carbon, hydrogen, and oxygen. If the glucose weighs 180 amu, what is the molecular formula of glucose? C = 12 ; H = 1 ; O = 16 A. C6H12O6

B. C4H8O4

C. C2H4O2

D. C5H10O5

11. Calculate the mass of Ba(OH)2 required to prepare 2.50L of a 0.0600 M solution of barium hydroxide. Ba = 137.34 ; O = 16 ; H = 1 A. 0.15 g

B. 150 g

C. 25.70 g

D. 257.0 g

12. How many mL of 18.0 M H2SO4 are required to prepare 1.00L of 0.900M solution of sulfuric acid? H = 1 ; S = 32 ; O = 16 A. 50

B. 500

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C. 16.2

D. 162

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Basic Chemistry & Elementary Chemical Engineering Review Questions 13. What is the molality of a solution that contains 128 g of CH 3OH in 108 g of water? C = 12 ; H = 1 ; O = 16 A. 0.03704

B. 1185.19

C. 296.30

D. 37.04

14. How many grams of H2O must be used to dissolve 50.0 g of sucrose to prepare a 1.25 m solution of sucrose, C12H22O11? C = 12 ; H = 1; O = 16 A. 40

B. 116.96

C. 5.472

D. 124.03

15. Calculate the normality of a solution of 4.202 grams of HNO3 in 600 mL of solution. H = 1 ; N = 14 ; O = 16 A. 7.003

B. 0.00011

C. 0.1112

D. 0.2223

16. Calculate the normality of a solution that contains 9.50 grams of barium hydroxide, Ba(OH)2 in 2000 mL of solution. Ba = 137.34 ; O = 16 ; H = 1 A. 0.0544

B. 0.0277

C. 4.75

D. 9.5

17. Calculate the density of a mixture formed by mixing 20.0 liters of nitrobenzene (SG = 1.20) with 3.00 ft3 of benzene (SG = 0.879), assuming that the volume of the mixture is the sum of the two feed component volumes. A. 1.158 kg/L

B. 1.20 kg/L

C. 0.0904 kg/L D. 0.94 kg/L

18. At 10 deg C, pure nitric acid has a specific gravity of 1.531, and an aqueous solution containing 40.0 wt% HNO3 has a specific gravity of 1.256. Calculate the required quantity (in liters) of 40% solution that contains exactly 31.50 g HNO3. A. 78.75

B. 0.06270

C. 0.07875

D. 0.01595

19. The density of sulfuric acid solution taken from a car battery is 1.225 g/cm3. This corresponds to a 3.75M solution. Express the concentration of this solution in terms of mole fraction of H 2SO4, and percentage of water by mass. H2SO4 =98 ; H2O = 18 A. B. C. D.

X = 0.07297 ; %H2O = 70% X = 0.3 ; %H2O = 70% X =0.07872 ; %H2O = 92.70% X = 0.07297 ; %H2O = 92.70%

20. The density of an aqueous solution containing 12.50 grams K2SO4 in 100g solution is 1.083 g/mL. Calculate the concentration of this solution in terms of %K2SO4, and mole fraction of solvent. K2SO4 = 174 ; H2O = 18 A. B. C. D.

% K2SO4 = 14.29%; X = 0.9854 % K2SO4 = 12.50%; X = 0.1408 % K2SO4 = 12.50%; X = 0.9854 % K2SO4 = 11.30%; X = 0.9854

21. What mass of oxygen (O2 = 32) is required to react completely with 1.20 mol of CH4 (MW = 16)?

A. 38.4 g

B. 19.2 g

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CH4 + O2 ~> CO2 + H2O C. 9.6 g D. 76.8 g

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Basic Chemistry & Elementary Chemical Engineering Review Questions 22. Phosphorus, P4 (MW = 124), burns with excess oxygen to form tetraphosphorus decoxide, P4O10 (MW = 284). In this reaction, what mass of P4 reacts with 1.50 moles of O2 (MW = 32)?

A. 186 g

B. 93 g

P4 + O2 ~> P4O10 C. 85.2 g D. 37.2 g

23. The following reaction takes place at high temperatures. Cr2O3 (s) + 2Al (l) ~> 2Cr (l) + Al2O3 (l) If 42.7 g Cr2O3 (MW = 152) and 9.8 g Al (MW = 27) are mixed and reacted until one of the reactants is used up, how many grams of chromium (MW = 52) will be formed? A. 82.24 g

B. 41.12 g

C. 37.75 g

D. 18.87 g

24. What is the maximum mass of Ni(OH)2 (MW = 92.71) that could be prepared by mixing two solutions that contain 25.9 g of NiCl2 (MW = 129.61) and 10.0 g of NaOH (MW = 40), respectively.

A. 11.59 g

B. 18.53 g

NiCl2 + 2NaOH ~> Ni(OH)2 + 2NaCl C. 9.26 g D. 23.18 g

25. Calculate the volume in Liters of a 0.324M solution of sulfuric acid (MW = 98) required to react completely with 2.792 g of Na2CO3 (MW = 106) according to the equation

A. 0.08130

H2SO4 + Na2CO3 ~> Na2SO4 + CO2 + H2O B. 0.08793 C. 0.02849 D. 0.02634

26. Calculate the number of grams of carbon dioxide, CO2 (MW = 44) that can react with 43.44 mL of a 0.957 M solution of potassium hydroxide, KOH (MW = 56), according to the following reaction:

A. 0.91460

B. 914.60

2KOH + CO2 ~> K2CO3 + H2O C. 1.8292 D. 2.3280

27. What is the molarity of a hydrochloric acid solution if 36.7 mL of the HCl (MW = 36.45) solution is required to react with 43.2 mL of 0.236 M sodium hydroxide, NaOH (MW = 40). HCl + NaOH ~> NaCl + H2O A. 0.1389

B. 4.988

C. 0.2778

D. 2.494

28. A 43.2 mL sample of 0.236 M sodium hydroxide solution (NaOH aq., MW = 40) reacts completely with 36.7 mL of a sulfuric acid solution. What is the molarity of the H 2SO4 (MW = 98) solution? H2SO4 + 2NaOH ~> Na2SO4 + 2H2O A. 4.988

B. 0.1389

C. 2.494

D. 0.2778

29. What mass of potassium chlorate is required to supply the proper amount of oxygen needed to burn 66.3 g of methane, CH4? K = 39; Cl = 35.45; O = 16; C = 12; H = 1

A. 610.24 g

B. 338.27 g

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2KClO3 ~> 2KCl +3O2 CH4 + 2O2 ~> CO2 + 2H2O C. 169.13 g D. 676.54 g

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Basic Chemistry & Elementary Chemical Engineering Review Questions 30. Ammonium nitrate (NH4NO3, MW = 80), known for its use in agriculture, can be produced from ammonia (NH3, MW = 17) by the following sequence of reactions: N = 14; H = 1; O = 16 4NH3 + 5O2 ~> 4NO + 6H2O 2NO + O2 ~> 2NO2 3NO2 + H2O ~> 2HNO3 + NO HNO3 + NH3 ~> NH4NO3 How much ammonia is needed to 500.0 g of ammonium nitrate? A. 106.25 g

B. 159.38 g

C. 53.13 g

D. 70.83 g

31. A gas sample contained in a cylinder equipped with a moveable piston occupied 300.0 mL at a pressure of 2.0 atm. What would be the final pressure if the volume were increased to 550.0 mL at constant temperature? A. 3.67 atm

B. 1.26 atm

C. 1.09 atm

D. 2.88 atm

32. Several balloons are inflated with helium to a volume of 0.85 L at 27 deg. C. One of the balloons was found several hours later; the temperature had dropped to 22 deg. C. What would be the volume of the balloon when found, if no helium has escaped? A. 0.8358 L

B. 0.8644 L

C. 0.6926 L

D. 1.0432 L

33. A cylinder with a movable piston contains 2.00 g of helium, He, at room temperature. More helium was added to the cylinder and the volume was adjusted so that the gas pressure remained the same. How many grams of helium were added to the cylinder if the volume was changed from 2.00 L to 2.70 L? (The temperature was held constant.) A. 2.00 g

B. 1.48 g

C. 1.67 g

D. 2.70 g

34. A researcher is studying the relationship between volume of burps and stress. Burps due to stress are just swallowed air. Your diaphragm detects pressure as discomfort at 210.0 kPa. (body temperature is 37 oC). If you feel discomfort and you burp, into the researcher’s balloon, the balloon slightly inflates to 6.45 mL at 101.3 kPa and 27 oC. What volume did the burp occupy in your body? A. 3.01 mL

B. 2.27 mL

C. 3.22 mL

D. 4.26 mL

35. An aerosol can contain 400.0 ml of compressed gas at 5.2 atm pressure. When the gas is sprayed into a large plastic bag, the bag inflates to a volume of 2.14 L. What is the pressure of gas inside the plastic bag? A. 0.9720 atm B. 971.96 kPa

C. 27.82 kPa

D. 1.302 atm

36. A gaseous mixture at STP contains 5.23 g of chloroform, CHCl3, and 1.66 g of methane, CH4. What is the total pressure contributed by the mixture? C = 12; H = 1; Cl = 35.45 A. 0.8623 atm B. 0.3354 atm C. 0.1493 atm D. 0.7120 atm 37. It is the pressure relative to atmospheric pressure. A reading of zero shows that the internal pressure is the same as that of the external pressure. A. Gauge pressure

B. Hydrostatic pressure

C. Absolute pressure

D. Vacuum

38. One thousand kilograms per hour of a mixture of benzene (B) and toluene (T) that contains 50% benzene by mass are separated by distillation into two fractions. The mass flow rate of benzene

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Basic Chemistry & Elementary Chemical Engineering Review Questions in the top stream is 450 kg/hr, and that of toluene in the bottom stream is 475 kg/hr. The operation is at steady state. What are the missing output streams? A. B. C. D.

Qbenzene = 25 kg/hr; Qtoluene = 50 kg/hr Qbenzene = 50 kg/hr; Qtoluene = 25 kg/hr Qbenzene = 30 kg/hr; Qtoluene = 45 kg/hr Qbenzene = 75 kg/hr; Qtoluene = 50 kg/hr

39. Two methanol-water mixtures are contained in separate flasks. The first mixture contains 40 wt% methanol, and the second contains 70 wt% methanol. If 200g of the first mixture are combined with 150 g of the second, what are the mass and composition of the product? A. B. C. D.

M = 300 g; %MetOH = 47.14% M = 350 g; %MetOH = 52.86% M = 150 g; %MetOH = 52.86% M = 350 g; %MetOH = 47.14%

40. A humid air is desired for a particular biological experiment. The input streams are: a) Liquid water, fed at a rate of 20 cu. cm per min b) Air (21 mole% O2, 79 mole% N2) c) Pure oxygen, with molar flow rate one fifth of the molar flow rate of stream B. The output gas is found to contain 1.5 mole% water. What is the exit mole% concentration of O2? A. 66.35

B. 33.65

C. 43.88

D. 56.12

41. A unit process of extracting solids from a solid material by dissolving it using a liquid solvent. A. Gas Absorption

B. Liquid-Liquid Extraction

C. Drying

D. Leaching

42. A sedimentation process is to be used to separate pulverized coal from slate. A suspension of finely divided particles of galena (lead sulfide, SG = 7.44) in water is prepared, with an overall SG of 1.48. A mixture of coal and slate is placed in the suspension; the coal rises to the top, and the slate sinks. How much galena must be added to 2500 kg of water to produce a suspension of the desired specific gravity? A. 4600 kg

B. 3500 kg

C. 2800 kg

D. 1500 kg

43. A gas containing equal parts (on a molar basis) of H2, N2, and H2O is passed through a column of calcium chloride pellets, which absorb 97% of the water and none of the other gases. The column packing was initially dry and had a mass of 2.00 kg. Following 6 hr of continuous operation, the pellets are reweighed and are found to have a mass of 2.21 kg. Calculate the molar flow rate (mol/hr) of the feed gas. A. 12

B. 36

C. 6

D. 24

44. Wet sugar contains 20% water is sent through a dryer in which 75% of the water is removed. Calculate the ratio of kg H2O removed per kg wet sugar leaving the dryer. A. 3/17

B. 17/3

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C. 1/3

D. 1/17

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Basic Chemistry & Elementary Chemical Engineering Review Questions 45. A labelled flowchart of a continuous steady-state two-unit distillation process is shown below. Each stream contains two components, A and B, in different proportions. Calculate the unknown flow rate and %concentration of A exiting at unit 2.

A. B. C. D.

P = 30 kg/hr; %x = 25.56 P = 60 kg/hr; %x = 8.33 P = 60 kg/hr; %x = 23.33 P = 30 kg/hr; %x = 8.33

46. Seawater containing 3.50 wt% salt passes through a series of 10 evaporators. Roughly equal quantities of water are vaporized in each of the 10 units and are then condensed and combined to obtain a product of fresh water. The brine at the outlet of the last evaporator contains 5.00 wt% salt. If 30,000 kg/hr of seawater are fed to the process, calculate the fractional yield of fresh water leaving the 4th evaporator. A. 0.03845

B. 0.03429

C. 0.02723

D. 0.02608

47. One hundred gram-moles of ethane are fed to the reactor. The product stream is analyzed for hydrogen, and it is found that the molar flow rate of H2 is 40 mol/min. What is the exiting flow rate of ethene? C2H6 ~> H2 + C2H4 (dehydrogenation process) A. 60 mol/min B. 50 mol/min C. 40 mol/min D. 70 mol/min 48. Methane is burned with oxygen to yield carbon dioxide and water. The feed contains 20 mole% CH4, 60% O2, and 20%CO2, and a 90% conversion of the limiting reactant is achieved. Calculate the total moles of the product stream. A. 116 mol

B. 76 mol

C. 84 mol

D. 96 mol

49. It is a process wherein a fraction of the feed is diverted around a unit and combined with the output stream from the unit. A. Bypass

B. Purge

C. Recycle

D. Channelling

50. Forty-five hundred kilograms per hour of a solution that is 33.3% K2CrO4 by mass is joined by a recycle stream containing 36.36% K2CrO4, and the combined stream is fed to an evaporator. The concentrated stream that leaves the evaporator contains 49.4% K2CrO4; this stream is fed to a crystallizer in which it is cooled (causing crystals of K2CrO4 to come out of the solution) and then filtered. The filter cake contains K2CrO4 crystals and a solution that contains 36.36% K2CrO4 by mass; the crystals account for 95% of the total mass of the filter cake. Calculate the ratio of the recycle to the fresh feed. A. 0.88

B. 2.63

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C. 1.25

D. 1.9

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