Chemical Engineering Chapter 3 1 Lead (II) nitrate is a poisonous substance which has been used in the manufacture of special explosives and as a sensitizer in photography. Calculate the mass of lead in

Chapter 3: Stoichiometry of Formulas and Equations

1. Calcium fluoride, CaF2, is a source of fluorine and is used to fluoridate drinking water.

Calculate its molar mass.

A) 118.15 g/mol D) 59.08 g/mol

B) 99.15 g/mol E) 50.01 g/mol

C) 78.07 g/mol

2. Calculate the molar mass of tetraphosphorus decaoxide, P4O10, a corrosive substance

which can be used as a drying agent.

A) 469.73 g/mol D) 139.88 g/mol

B) 283.89 g/mol E) 94.97 g/mol

C) 190.97 g/mol

3. Calculate the molar mass of rubidium carbonate, Rb2CO3.

A) 340.43 g/mol D) 145.47 g/mol

B) 255.00 g/mol E) 113.48 g/mol

C) 230.94 g/mol

4. Calculate the molar mass of (NH4)3AsO4.

A) 417.80 g/mol D) 156.96 g/mol

B) 193.03 g/mol E) 108.96 g/mol

C) 165.02 g/mol

5. Aluminum sulfate, Al2(SO4)3, is used in tanning leather, purifying water, and

manufacture of antiperspirants. Calculate its molar mass.

A) 450.06 g/mol D) 278.02 g/mol

B) 342.15 g/mol E) 74.98 g/mol

C) 315.15 g/mol

6. Calculate the molar mass of Ca(BO2)2·6H2O.

A) 273.87 g/mol D) 174.89 g/mol

B) 233.79 g/mol E) 143.71 g/mol

C) 183.79 g/mol

Chapter 3: Stoichiometry of Formulas and Equations

7. Magnesium fluoride is used in the ceramics and glass industry. What is the mass of 1.72

mol of magnesium fluoride?

A) 43.3 g B) 62.3 g C) 74.5 g D) 92.9 g E) 107 g

8. Sodium bromate is used in a mixture which dissolves gold from its ores. Calculate the

mass in grams of 4.68 mol of sodium bromate.

A) 706 g B) 482 g C) 383 g D) 32.2 g E) 0.0310 g

9. What is the mass in grams of 0.250 mol of the common antacid calcium carbonate?

A) 4.00 × 102 g

B) 25.0 g

C) 17.0 g

D) 4.00 × 10–2 g

E) 2.50 × 10–3 g

10. Calculate the number of moles in 17.8 g of the antacid magnesium hydroxide, Mg(OH)2.

A) 3.28 mol B) 2.32 mol C) 0.431 mol D) 0.305 mol E) 0.200 mol

11. Phosphorus pentachloride, PCl5, a white solid that has a pungent, unpleasant odor, is

used as a catalyst for certain organic reactions. Calculate the number of moles in 38.7 g of PCl5.

A) 5.38 mol B) 3.55 mol C) 0.583 mol D) 0.282 mol E) 0.186 mol

12. Aluminum oxide, Al2O3, is used as a filler for paints and varnishes as well as in the

manufacture of electrical insulators. Calculate the number of moles in 47.51 g of Al2O3.

A) 2.377 mol

B) 2.146 mol

C) 1.105 mol

D) 0.4660 mol

E) 0.4207 mol

13. Which of the following samples has the most moles of the compound?

A) 50.0 g of Li2O D) 50.0 g of CO2

B) 75.0 g of CaO E) 100.0 g of SO3

C) 200.0 g of Fe2O3

Chapter 3: Stoichiometry of Formulas and Equations

14. Calculate the number of oxygen atoms in 29.34 g of sodium sulfate, Na2SO4.

A) 1.244 × 1023 O atoms D) 2.915 × 1024 O atoms

B) 4.976 × 1023 O atoms E) 1.166 × 1025 O atoms

C) 2.409 × 1024 O atoms

15. A normal breath takes in about 1.0 L of air. Assuming that air has an average molar mass

of 28.8 g, and that its density is 0.97 g/L, how many molecules of air do you take in with each

breath?

A) 2.0 × 1022 B) 2.2 × 1022 C) 5.8 × 1023 D) 1.7 × 1025 E) 1.8 × 1025

16. Which of the following samples contains the greatest total number atoms?

A) 50.0 g of Li2O D) 50.0 g of CO2

B) 75.0 g of CaO E) 100.0 g of SO3

C) 200.0 g of Fe2O3

17. A single atom of hydrogen has a mass of 1.0 amu, while a mole of hydrogen atoms has a

mass of 1.0 g. Select the correct conversion factor between atomic mass units and grams.

A) 1 amu = 1 g exactly D) 1 g = 1.7 × 10–24 amu

B) 1 amu = 6.0 × 1023 g E) none of the above

C) 1 g = 6.0 × 1023 amu

18. How many atoms are in a drop of mercury that has a diameter of 1.0 mm? (Volume of a

sphere is 4r3/3; density of mercury = 13.6 g/cm3)

A) 2.1 × 1019 D) 1.7 × 1023

B) 1.7 × 1020 E) none of the above

C) 2.1 × 1022

19. Potassium dichromate, K2Cr2O7, is used in tanning leather, decorating porcelain, and

water proofing fabrics. Calculate the number of chromium atoms in 78.82 g of K2Cr2O7.

A) 9.490 × 1025 Cr atoms D) 3.227 × 1023 Cr atoms

B) 2.248 × 1024 Cr atoms E) 1.613 × 1023 Cr atoms

C) 1.124 × 1024 Cr atoms

Chapter 3: Stoichiometry of Formulas and Equations

20. Sulfur trioxide can react with atmospheric water vapor to form sulfuric acid that falls as

acid rain. Calculate the mass in grams of 3.65 × 1020 molecules of SO3.

A) 6.06 × 10–4 g

B) 2.91 × 10–2 g

C) 4.85 × 10–2 g

D) 20.6 g

E) 1650 g

21. Calculate the mass in grams of 8.35 × 1022 molecules of CBr4.

A) 0.0217 g B) 0.139 g C) 7.21 g D) 12.7 g E) 46.0 g

22. The number of hydrogen atoms in 0.050 mol of C3H8O3 is

A) 3.0 × 1022 H atoms. D) 4.8 × 1023 H atoms.

B) 1.2 × 1023 H atoms. E) none of the above.

C) 2.4 × 1023 H atoms.

23. How many protons are there in a molecule of adrenaline (C9H13NO3), a neurotransmitter

and hormone?

A) 22 B) 26 C) 43 D) 98 E) 183

24. Copper(II) sulfate pentahydrate, CuSO4·5H2O, is used as a fungicide and algicide.

Calculate the mass of oxygen in 1.000 mol of CuSO4·5H2O.

A) 249.7 g B) 144.0 g C) 96.00 g D) 80.00 g E) 64.00 g

25. Lead (II) nitrate is a poisonous substance which has been used in the manufacture of

special explosives and as a sensitizer in photography. Calculate the mass of lead in 139 g of

Pb(NO3)2.

A) 107 g B) 90.8 g C) 87.0 g D) 83.4 g E) 62.6 g

26. Household sugar, sucrose, has the molecular formula C12H22O11. What is the % of

carbon in sucrose, by mass?

A) 26.7% B) 33.3% C) 41.4% D) 42.1% E) 52.8%

27. Determine the percent composition of potassium dichromate, K2Cr2O7.

A) 17.5% K, 46.6% Cr, 35.9% O D) 37.2% K, 24.7% Cr, 38.1% O

B) 29.8% K, 39.7% Cr, 30.5% O E) none of the above

C) 36.5% K, 48.6% Cr, 14.9% O

Chapter 3: Stoichiometry of Formulas and Equations

Page 35

28. Gadolinium oxide, a colorless powder which absorbs carbon dioxide from the air,

contains 86.76 mass % Gd. Determine its empirical formula.

A) Gd2O3 B) Gd3O2 C) Gd3O4 D) Gd4O3 E) GdO

29. Hydroxylamine nitrate contains 29.17 mass % N, 4.20 mass % H, and 66.63 mass % O.

Determine its empirical formula.

A) HNO B) H2NO2 C) HN6O16 D) HN16O7 E) H2NO3

30. Hydroxylamine nitrate contains 29.17 mass % N, 4.20 mass % H, and 66.63 mass O. If

its molar mass is between 94 and 98 g/mol, what is its molecular formula?

A) NH2O5 B) N2H4O4 C) N3H3O3 D) N4H8O2 E) N2H2O4

31. Analysis of a carbohydrate showed that it consisted of 40.0 % C, 6.71 % H, and 53.3 %

O by mass. Its molecular mass was found to be between 140 and 160 amu. What is the

molecular formula of this compound?

A) C4H8O6

B) C5H10O5

C) C5H12O5

D) C6H12O4

E) none of the above

32. A compound of bromine and fluorine is used to make UF6, which is an important

chemical in processing and reprocessing of nuclear fuel. The compound contains 58.37 mass

percent bromine. Determine its empirical formula.

A) BrF B) BrF2 C) Br2F3 D) Br3F E) BrF3

33. A compound containing chromium and silicon contains 73.52 mass percent chromium.

Determine its empirical formula.

A) CrSi3 B) Cr2Si3 C) Cr3Si D) Cr3Si2 E) Cr2S

34. Alkanes are compounds of carbon and hydrogen with the general formula CnH2n+2. An

alkane component of gasoline has a molar mass of between 125 and 130 g/mol. What is the

value of n for this alkane?

Chapter 3: Stoichiometry of Formulas and Equations

35. Terephthalic acid, used in the production of polyester fibers and films, is composed of

carbon, hydrogen, and oxygen. When 0.6943 g of terephthalic acid was subjected to combustion

analysis it produced 1.471 g CO2 and 0.226 g H2O. What is its empirical formula?

A) C2H3O4 B) C3H4O2 C) C4H3O2 D) C5H12O4 E) C2H2O

36. Terephthalic acid, used in the production of polyester fibers and films, is composed of

carbon, hydrogen, and oxygen. When 0.6943 g of terephthalic acid was subjected to combustion

analysis it produced 1.471 g CO2 and 0.226 g H2O. If its molar mass is between 158 and 167

g/mol, what is its molecular formula?

A) C4H6O7 B) C6H8O5 C) C7H12O4 D) C4H3O2 E) C8H6O4

37. Hydroxylamine hydrochloride is a powerful reducing agent which is used as a

polymerization catalyst. It contains 5.80 mass % H, 20.16 mass % N, 23.02 mass % O, and

51.02 mass % Cl. What is its empirical formula?

A) H2N7O8Cl18

B) H2N2O2Cl

C) HN3O4Cl9

D) H4NOCl

E) H4NOCl2

38. In the combustion analysis of 0.1127 g of glucose (C6H12O6), what mass, in grams, of

CO2 would be produced?

A) 0.0451 g B) 0.0825 g C) 0.1652 g D) 0.4132 g E) 1.466 g

39. Balance the following equation:

B2O3(s) + HF(l) → BF3(g) + H2O(l)

A) B2O3(s) + 6HF(l) → 2BF3(g) + 3H2O(l)

B) B2O3(s) + H6F6(l) → B2F6(g) + H6O3(l)

C) B2O3(s) + 2HF(l) → 2BF3(g) + H2O(l)

D) B2O3(s) + 3HF(l) → 2BF3(g) + 3H2O(l)

E) B2O3(s) + 6HF(l) → 2BF3(g) + 6H2O(l)

40. Balance the following equation:

UO2(s) + HF(l) → UF4(s) + H2O(l)

A) UO2(s) + 2HF(l) → UF4(s) + H2O(l)

B) UO2(s) + 4HF(l) → UF4(s) + 2H2O(l)

C) UO2 (s) + H4F4(l) → UF4 (s) + H4O2(l)

D) UO2(s) + 4HF(l) → UF4(s) + 4H2O(l)

E) UO2(s) + 8HF(l) → 2UF4(s) + 4H2O(l)

Chapter 3: Stoichiometry of Formulas and Equations

41. Balance the following equation for the combustion of benzene:

C6H6(l) + O2(g) → H2O(g) + CO2(g)

A) C6H6(l) + 9O2(g) → 3H2O(g) + 6CO2(g)

B) C6H6(l) + 9O2(g) → 6H2O(g) + 6CO2(g)

C) 2C6H6(l) + 15O2(g) → 6H2O(g) + 12CO2(g)

D) C6H6(l) + 15O2(g) → 3H2O(g) + 6CO2(g)

E) 2C6H6(l) + 9O2(g) → 6H2O(g) + 12CO2(g)

42. Balance the following equation:

C8H18O3(l) + O2(g) → H2O(g) + CO2(g)

A) C8H18O3(l) + 8O2(g) → 9H2O(g) + 8CO2(g)

B) C8H18O3(l) + 11O2(g) → 9H2O(g) + 8CO2(g)

C) 2C8H18O3(l) + 22O2(g) → 9H2O(g) + 16CO2(g)

D) C8H18O3(l) + 13O2(g) → 18H2O(g) + 8CO2(g)

E) 2C8H18O3(l) + 17O2(g) → 18H2O(g) + 16CO2(g)

43. Balance the following equation:

Ca3(PO4)2(s) + SiO2(s) + C(s) → CaSiO3(s) + CO(g) + P4(s)

A) Ca3(PO4)2(s) + 3SiO2(s) + 8C(s) → 3CaSiO3(s) + 8CO(g) +

P4(s)

B) Ca3(PO4)2(s) + 3SiO2(s) + 14C(s) → 3CaSiO3(s) + 14CO(g) +

P4(s)

C) Ca3(PO4)2(s) + 3SiO2(s) + 8C(s) → 3CaSiO3(s) + 8CO(g) +

2P4(s)

D) 2Ca3(PO4)2(s) + 6SiO2(s) + 10C(s) → 6CaSiO3(s) + 10CO(g) +

P4(s)

E) 2Ca3(PO4)2(s) + 6SiO2(s) + 10C(s) → 6CaSiO3(s) + 10CO(g) +

4P4(s)

44. How many molecules of molecular oxygen react with four molecules of NH3 to form

four molecules of nitrogen monoxide and six molecules of water?

A) 2 B) 10 C) 3 D) 4 E) 5

Chapter 3: Stoichiometry of Formulas and Equations

45. Sulfur dioxide reacts with chlorine to produce thionyl chloride (used as a drying agent for

inorganic halides) and dichlorine oxide (used as a bleach for wood, pulp, and textiles).

SO2(g) + 2Cl2(g) → SOCl2(g) + Cl2O(g)

If 0.400 mol of Cl2 reacts with excess SO2, how many moles of Cl2O are formed?

A) 0.800 mol

B) 0.400 mol

C) 0.200 mol

D) 0.100 mol

E) 0.0500 mol

46. Aluminum will react with bromine to form aluminum bromide (used as an acid catalyst in

organic synthesis).

Al(s) + Br2(l) → Al2Br6(s) [unbalanced]

How many moles of Al are needed to form 2.43 mol of Al2Br6?

A) 7.29 mol B) 4.86 mol C) 2.43 mol D) 1.62 mol E) 1.22 mol

47. Ammonia will react with fluorine to produce dinitrogen tetrafluoride and hydrogen

fluoride (used in production of aluminum, in uranium processing, and in frosting of light bulbs).

2NH3(g) + 5F2(g) → N2F4(g) + 6HF(g)

How many moles of NH3 are needed to react completely with 13.6 mol of F2?

A) 34.0 mol B) 27.2 mol C) 6.80 mol D) 5.44 mol E) 2.27 mol

48. Ammonia, an important source of fixed nitrogen that can be metabolized by plants, is

produced using the Haber process in which nitrogen and hydrogen combine.

N2(g) + 3H2(g) → 2NH3(g)

How many grams of nitrogen are needed to produce 325 grams of ammonia?

A) 1070 g B) 535 g C) 267 g D) 178 g E) 108 g

49. How many grams of sodium fluoride (used in water fluoridation and manufacture of

insecticides) are needed to form 485 g of sulfur tetrafluoride?

3SCl2(l) + 4NaF(s) → SF4(g) + S2Cl2(l) + 4NaCl(s)

A) 1940 g B) 1510 g C) 754 g D) 205 g E) 51.3 g

50. How many grams of oxygen are needed to react completely with 200.0 g of ammonia,

NH3?

4NH3(g) + 5O2(g) → 4NO(g) + 6H2O(g)

A) 469.7 g B) 300.6 g C) 250.0 g D) 3.406 g E) 2.180 g

Chapter 3: Stoichiometry of Formulas and Equations

51. Phosphine, an extremely poisonous and highly reactive gas, will react with oxygen to

form tetraphosphorus decaoxide and water.

PH3(g) + O2(g) → P4O10(s) + H2O(g) [unbalanced]

Calculate the mass of P4O10(s) formed when 225 g of PH3 reacts with excess oxygen.

A) 1880 g B) 940. g C) 900. g D) 470 g E) 56.3 g

52. Potassium chlorate (used in fireworks, flares, and safety matches) forms oxygen and

potassium chloride when heated.

KClO3(s) → KCl(s) + O2(g) [unbalanced]

How many grams of oxygen are formed when 26.4 g of potassium chlorate is heated?

A) 223 g B) 99.1 g C) 10.3 g D) 6.86 g E) 4.60 g

53. Aluminum metal reacts with chlorine gas to form solid aluminum trichloride, AlCl3.

What mass of chlorine gas is needed to react completely with 163 g of aluminum?

A) 214 g B) 245 g C) 321 g D) 489 g E) 643 g

54. Lead(II) sulfide was once used in glazing earthenware. It will also react with hydrogen

peroxide to form lead(II) sulfate and water. How many grams of hydrogen peroxide are needed

to react completely with 265 g of lead(II) sulfide?

A) 151 g B) 123 g C) 50.3 g D) 37.7 g E) 9.41 g

55. An important reaction sequence in the industrial production of nitric acid is the

following:

N2(g) + 3H2(g) → 2NH3(g)

4NH3(g) + 5O2(g) → 4NO(g) + 6H2O(l)

Starting from 20.0 mol of nitrogen gas in the first reaction, how many moles of oxygen gas are

required in the second one?

A) 12.5 mol O2 D) 50.0 mol O2

B) 20.0 mol O2 E) 100. mol O2

C) 25.0 mol O2

Chapter 3: Stoichiometry of Formulas and Equations

56. In a blast furnace, elemental iron is produced from a mixture of coke (C), iron ore

(Fe3O4), and other reactants. An important reaction sequence is

2C(s) + O2(g) → 2CO(g)

Fe3O4(s) + 4CO(g) → 3Fe(l) + 4CO2(g)

How many moles of iron can be formed in this sequence when 1.00 mol of carbon, as coke, is

consumed?

A) 6.00 mol Fe D) 1.25 mol Fe

B) 3.00 mol Fe E) 0.750 mol Fe

C) 1.33 mol Fe

57. The iodine “clock reaction” involves the following sequence of reactions occurring in a

reaction mixture in a single beaker.

1. IO3–(aq) + 5I–(aq) + 6H+(aq) → 3I2(aq) + 3H2O(l)

2. I2(aq) + 2S2O32-(aq) → 2I–(aq) + S4O62-(aq)

The molecular iodine (I2) formed in reaction 1 is immediately used up in reaction 2, so that no

iodine accumulates. What is the overall reaction occurring in this experiment?

A) IO3–(aq) + 3I–(aq) + 2S2O32-(aq) + 6H+(aq) → 2I2(aq) + S4O62-(aq) +

3H2O(l)

B) IO3–(aq) + 4S2O32-(aq) + 6H+(aq) → I–(aq) + 2S4O62-(aq) + 3H2O(l)

C) IO3–(aq) + 6S2O32-(aq) + 6H+(aq) → I–(aq) + 3S4O62-(aq) + 3H2O(l)

D) IO3–(aq) + I2(aq) + 8S2O32-(aq) + 6H+(aq) → 3I–(aq) + 4S4O62-(aq) +

3H2O(l)

E) IO3–(aq) + 2I2(aq) + 6S2O32-(aq) + 6H+(aq) → 5I–(aq) + 3S4O62-(aq) +

3H2O(l)

58. The iodine “clock reaction” involves the following sequence of reactions occurring in a

reaction mixture in a single beaker.

1. IO3–(aq) + 5I–(aq) + 6H+(aq) → 3I2(aq) + 3H2O(l)

2. I2(aq) + 2S2O32-(aq) → 2I–(aq) + S4O62-(aq)

The molecular iodine (I2) formed in reaction 1 is immediately used up in reaction 2, so that no

iodine accumulates. In one experiment, a student made up a reaction mixture which initially

contained 0.0020 mol of iodate ions (IO3–). If the iodate ions reacted completely, how many

moles of thiosulfate ions (S2O32-) were needed in reaction 2, in order to react completely with

the iodine (I2) produced in reaction 1?

A) 0.0020 mol D) 0.0050 mol

B) 0.0030 mol E) 0.0060 mol

C) 0.0040 mol

Chapter 3: Stoichiometry of Formulas and Equations

59. Aluminum oxide (used as an adsorbent or a catalyst for organic reactions) forms when

aluminum reacts with oxygen.

4Al(s) + 3O2(g) → 2Al2O3(s)

A mixture of 82.49 g of aluminum ( = 26.98 g/mol) and 117.65 g of oxygen ( = 32.00

g/mol) is allowed to react. What mass of aluminum oxide ( = 101.96 g/mol) can be formed?

A) 155.8 g B) 200.2 g C) 249.9 g D) 311.7 g E) 374.9 g

60. Aluminum reacts with oxygen to produce aluminum oxide which can be used as an

adsorbent, desiccant, or catalyst for organic reactions.

4Al(s) + 3O2(g) → 2Al2O3(s)

A mixture of 82.49 g of aluminum ( = 26.98 g/mol) and 117.65 g of oxygen ( = 32.00

g/mol) is allowed to react. Identify the limiting reactant and determine the mass of the excess

reactant present in the vessel when the reaction is complete.

A) Oxygen is the limiting reactant; 19.81 g of aluminum remain.

B) Oxygen is the limiting reactant; 35.16 g of aluminum remain.

C) Aluminum is the limiting reactant; 16.70 g of oxygen remain.

D) Aluminum is the limiting reactant; 35.16 g of oxygen remain.

E) Aluminum is the limiting reactant; 44.24 g of oxygen remain.

61. Magnesium reacts with iron(III) chloride to form magnesium chloride (which can be used

162.2 g/mol) is allowed to react. What mass of magnesium chloride = 95.21 g/mol) is formed?

A) 68.5 g MgCl2 D) 107 g MgCl2

B) 77.0 g MgCl2 E) 154 g MgCl2

C) 71.4 g MgCl2

62. Magnesium (used in the manufacture of light alloys) reacts with iron(III) chloride to form

magnesium chloride and iron.

162.2 g/mol) is allowed to react. Identify the limiting reactant and determine the mass of the

excess reactant present in the vessel when the reaction is complete.

A) Limiting reactant is Mg; 67 g of FeCl3 remain.

B) Limiting reactant is Mg; 134 g of FeCl3 remain.

C) Limiting reactant is Mg; 104 g of FeCl3 remain.

D) Limiting reactant is FeCl3; 2 g of Mg remain.

E) Limiting reactant is FeCl3; 87 g of Mg remain.

Chapter 3: Stoichiometry of Formulas and Equations

63. Potassium chloride is used as a substitute for sodium chloride for individuals with high

blood pressure. Identify the limiting reactant and determine the mass of the excess reactant

remaining when 7.00 g of chlorine gas reacts with 5.00 g of potassium to form potassium

chloride.

A) Potassium is the limiting reactant; 2.47 g of chlorine remain.

B) Potassium is the limiting reactant; 7.23 g of chlorine remain.

C) Chlorine is the limiting reactant; 4.64 g of potassium remain.

D) Chlorine is the limiting reactant; 2.70 g of potassium remain.

E) No limiting reagent: the reactants are present in the correct stoichiometric ratio.

64. Tetraphosphorus hexaoxide ( = 219.9 g/mol) is formed by the reaction of phosphorus

with oxygen gas.

P4(s) + 3O2(g) → P4O6(s)

If a mixture of 75.3 g of phosphorus and 38.7 g of oxygen produce 43.3 g of P4O6, what is the

percent yield for the reaction?

A) 57.5% B) 48.8% C) 38.0% D) 32.4% E) 16.3%

65. What is the percent yield for the reaction

PCl3(g) + Cl2(g) → PCl5(g)

if 119.3 g of PCl5 (M = 208.2 g/mol) are formed when 61.3 g of Cl2 ( = 70.91 g/mol) react

with excess PCl3?

A) 195% B) 85.0% C) 66.3% D) 51.4% E) 43.7%

66. Methanol (CH4O) is converted to bromomethane (CH3Br) as follows:

CH4O + HBr → CH3Br + H2O

If 12.23 g of bromomethane are produced when 5.00 g of methanol is reacted with excess HBr,

what is the percentage yield?

A) 40.9% B) 82.6% C) 100.% D) 121% E) 245%

67. Propane, C3H8, is commonly provided as a bottled gas for use as a fuel. In 0.200 mol of

propane

a. what is the mass of propane?

b. what mass of carbon is present?

c. how many molecules of C3H8 are present?

d. how many hydrogen atoms are present?

Chapter 3: Stoichiometry of Formulas and Equations

68. For a sample consisting of 2.50 g of methane, CH4, calculate

a. the number of moles of methane present.

b. the total number of atoms present.

69. In 0.20 mole of phosphoric acid, H3PO4

a. how many H atoms are there?

b. what is the total number of atoms?

c. how many moles of O atoms are there?

70. A compound consisting of C, H, and O only, has a molar mass of 331.5 g/mol.

Combustion of 0.1000 g of this compound caused a 0.2921 g increase in the mass of the CO2

absorber and a 0.0951 g increase in the mass of the H2O absorber. What is the empirical formula

of the compound?

71. Analysis of a white solid produced in a reaction between chlorine and phosphorus

showed that it contained 77.44% chlorine and 22.56% phosphorus. What is its empirical

formula?

72. Balance the following equation for the combustion of butane, a hydrocarbon used in gas

lighters:

C4H10(g) + O2(g) → CO2(g) + H2O(l)

73. Balance the equation

B2O3(s) + NaOH(aq) → Na3BO3(aq) + H2O(l)

74. Balance the following equation for partial oxidation of ammonia, an important reaction in

the production of nitric acid:

NH3(g) + O2(g) → NO(g) + H2O(l)

Chapter 3: Stoichiometry of Formulas and Equations

75. Gaseous methanol (CH4O) reacts with oxygen gas to produce carbon dioxide gas and

liquid water. Write a balanced equation for this process.

76. Consider the balanced equation for the combustion of propane, C3H8

C3H8(g) + 5O2(g) → 3CO2(g) + 4H2O(l)

If propane reacts with oxygen as above

a. what is the limiting reagent in a mixture containing 5.00 g of C3H8 and 10.0 g of O2?

b. what mass of CO2 is formed when 1.00 g of C3H8 reacts completely?

77. Ammonia, NH3, is produced industrially from nitrogen and hydrogen as follows:

N2(g) + 3H2(g) → 2NH3(g)

What mass, of which starting material, will remain when 30.0 g of N2 and 10.0 g of H2 react

until the limiting reagent is completely consumed?

78. Consider the balanced equation:

Al2S3(s) + 6H2O(l) → 2Al(OH)3(s) + 3H2S(g)

If 15.0g of aluminum sulfide and 10.0g of water are allowed to react as above, and assuming a

complete reaction

a. by calculation, find out which is the limiting reagent.

b. calculate the maximum mass of H2S which can be formed from these reagents.

c. calculate the mass of excess reagent remaining after the reaction is complete.

79. The insecticide DDT was formerly in widespread use, but now it is severely restricted

owing to its adverse environmental effects. It is prepared as follows:

C2HCl3O + 2C6H5Cl → C14H9Cl5 + H2O

chloral chlorobenzene DDT

If 10.00 g of chloral were reacted with 10.00 g of chlorobenzene

a. what is the maximum amount (mol) of DDT which could be formed?

b. what is the limiting reagent?

c. what is the % yield, if 12.15 g of DDT is produced?

Chapter 3: Stoichiometry of Formulas and Equations

80. One mole of O2 has a mass of 16.0 g.

81. One mole of methane (CH4) contains a total of 3 × 1024 atoms.

82. The formula CH3O0.5 is an example of an empirical formula.

83. In combustion analysis, the carbon and hydrogen contents of a substance are determined

from the CO2 and H2O, respectively, which are collected in the absorbers.

84. In combustion analysis, the oxygen content of a substance is equal to the total oxygen in

the CO2 and H2O collected in the absorbers.

85. Constitutional (structural) isomers have the same empirical formula but different

molecular formulas.

86. Constitutional (structural) isomers have the same molecular formula but different

structural formulas.

87. In a correctly balanced equation, the number of reactant molecules must equal the

number of product molecules.