A) / 12.00 amu
B) / 12.01 amu
C) / 6.00 amu
D) / 11.99 amu
2. / What information would you need to calculate the average atomic mass of an element?
A) / The number of neutrons in the element.
B) / The atomic number of the element.
C) / The mass and abundance of each isotope of the element.
D) / The position in the periodic table of the element.
3. / The atomic masses of Cl (75.53 percent) and Cl (24.47 percent) are 34.968 amu and 36.956 amu, respectively. Calculate the average atomic mass of chlorine. The percentages in parentheses denote the relative abundances.
A) / 35.96 amu
B) / 35.45 amu
C) / 36.47 amu
D) / 71.92 amu
4. / The atomic masses of Li and Li are 6.0151 amu and 7.0160 amu, respectively. Calculate the natural abundances of these two isotopes. The average atomic mass of Li is 6.941 amu.
A) / 6Li = 7.5 %; 7Li = 92.5 %
B) / 6Li = 0.075 %; 7Li = 99.025 %
C) / 6Li = 92.5 %; 7Li = 7.5 %
D) / 6Li = 25 %; 7Li = 75 %
5. / What is the mass in grams of 13.2 amu?
A) / 13.2 g
B) / 7.95 1023 g
C) / 13.2 10-23 g
D) / 2.19 10-23 g
6. / How many amu are there in 8.4 g?
A) / 8.4 1023 amu
B) / 1.4 10-23 amu
C) / 8.4 amu
D) / 5.1 1024 amu
7. / Earth's population is about 6.5 billion. Suppose that every person on Earth participates in a process of counting identical particles at the rate of two particles per second. How many years would it take to count 6.0 1023 particles? Assume that there are 365 days in a year.
A) / 1.3 1011 yr
B) / 1.5 106 yr
C) / 3.0 106 yr
D) / 3.6 107 yr
8. / The thickness of a piece of paper is 0.0036 in. Suppose a certain book has an Avogadro's number of pages; calculate the thickness of the book in light-years. (Hint: A light year is the distance traveled by light in one year, or 365 days, at a speed of 3.00 108 m/s)
A) / 2.2 1021 light-yr
B) / 6.0 1023 light-yr
C) / 5.8 103 light-yr
D) / 3.4 1016 light-yr
9. / How many atoms are there in 5.10 moles of sulfur (S)?
A) / 3.07 1024
B) / 9.59 1022
C) / 6.02 1023
D) / 9.82 1025
10. / How many moles of cobalt (Co) atoms are there in 6.00 109 (6 billion) Co atoms?
A) / 1 10-14
B) / 1.00 1014
C) / 9.96 10-15
D) / 3.61 1033
11. / How many moles of calcium (Ca) atoms are in 77.4 g of Ca?
A) / 4.66 1025 mol
B) / 1.93 mol
C) / 1.29 10-22 mol
D) / 0.518 mol
12. / How many grams of gold (Au) are there in 15.3 moles of Au?
A) / 9.21 1024 g
B) / 7.77 10-2 g
C) / 15.3 g
D) / 3.01 103 g
13. / What is the mass in grams of a single atom of Hg?
A) / 1.208 1026 g
B) / 3.002 1021 g
C) / 8.278 10-27 g
D) / 3.331 10-22 g
14. / What is the mass in grams of a single atom of As?
A) / 1.244 10-22 g
B) / 2.217 10-26 g
C) / 8.039 1021 g
D) / 4.510 1025 g
15. / What is the mass in grams of 1.00 1012 lead (Pb) atoms?
A) / 1.66 10-12 g
B) / 2.25 10-11 g
C) / 3.44 10-10 g
D) / 6.02 1011 g
16. / How many atoms are present in 3.14 g of copper (Cu)?
A) / 2.98 1022
B) / 1.92 1023
C) / 1.89 1024
D) / 6.02 1023
17. / Calculate the molecular mass (in amu) of CH4.
A) / 16.00 amu
B) / 12.01 amu
C) / 16.04 amu
D) / 16.33 amu
18. / Calculate the molecular mass (in amu) of SO3.
A) / 32.07 amu
B) / 80.07 amu
C) / 48.00 amu
D) / 192.21 amu
19. / Calculate the molar mass of Li2CO3.
A) / 73.89 g
B) / 66.95 g
C) / 41.89 g
D) / 96.02 g
20. / Calculate the molar mass of CS2.
A) / 44.08 g
B) / 12.01 g
C) / 64.14 g
D) / 76.15 g
21. / Calculate the molar mass of a compound if 0.372 mole of it has a mass of 152 g.
A) / 0.372 g/mol
B) / 152 g/mol
C) / 56.5 g/mol
D) / 409 g/mol
22. / How many molecules of ethane (C2H6) are present in 0.334 g of C2H6?
A) / 2.01 1023
B) / 6.69 1021
C) / 4.96 1022
D) / 8.89 1020
23. / Calculate the number of O atoms in 1.50 g of glucose (C6H12O6), a sugar.
A) / 9.03 1023
B) / 5.42 1024
C) / 3.01 1022
D) / 1.13 1024
24. / Urea [(NH2)2CO] is used for fertilizer and many other things. Calculate the number of N atoms in 1.68 104 g of urea.
A) / 3.37 1026
B) / 1.01 1028
C) / 6.02 1023
D) / 5.96 1025
25. / Pheromones are a special type of compound secreted by the females of many insect species to attract the males for mating. One pheromone has the molecular formula C19H38O. Normally, the amount of this pheromone secreted by a female insect is about 1.0 10-12 g. How many molecules are there in this quantity?
A) / 1.0 1012
B) / 6.0 1011
C) / 2.3 1010
D) / 2.1 109
26. / The density of water is 1.00 g/mL at 48° C. How many water molecules are present in 2.56 mL of water at this temperature?
A) / 1.54 1023
B) / 3.99 1024
C) / 6.99 1021
D) / 8.56 1022
27. / Carbon has two stable isotopes, C and C, and fluorine has only one stable isotope, F. How many peaks would you observe in the mass spectrum of the positive ion of ? Assume that the ion does not break up into smaller fragments.
A) / one
B) / five
C) / two
D) / four
28. / Hydrogen has two stable isotopes, H and H, and sulfur has four stable isotopes, S, S, S, S. How many peaks would you observe in the mass spectrum of the positive ion of hydrogen sulfide, H2S+? Assume no decomposition of the ion into smaller fragments.
A) / one
B) / seven
C) / six
D) / eight
29. / Tin (Sn) exists in Earth's crust as SnO2. Calculate the percent composition by mass of Sn in SnO2.
A) / 33.33 %
B) / 86.83 %
C) / 63.22 %
D) / 78.77 %
30. / For many years chloroform (CHCl3) was used as an inhalation anesthetic in spite of the fact that it is also a toxic substance that may cause severe liver, kidney, and heart damage. Calculate the percent composition by mass of Cl in this compound.
A) / 89.07 %
B) / 60.00 %
C) / 73.14 %
D) / 81.22 %
31. / Cinnamic alcohol is used mainly in perfumery, particularly in soaps and cosmetics. Its molecular formula is C9H10O. How many molecules of cinnamic alcohol are contained in a sample of mass 0.469 g?
A) / 9.35 1021
B) / 4.45 1022
C) / 2.11 1021
D) / 2.82 1023
32. / All of the substances listed below are fertilizers that contribute nitrogen to the soil. Which of these is the richest source of nitrogen on a mass percentage basis?
A) / Urea, (NH2)2CO
B) / Ammonium nitrate, NH4NO3
C) / Guanidine, HNC(NH2)2
D) / Ammonia, NH3
33. / Allicin is the compound responsible for the characteristic smell of garlic. An analysis of the compound gives the following percent composition by mass: C: 44.4 percent; H: 6.21 percent; S: 39.5 percent; O: 9.86 percent. What is its molecular formula given that its molar mass is about 162 g?
A) / C12H20S4O2
B) / C7H14SO
C) / C6H10S2O
D) / C5H12S2O2
34. / Peroxyacylnitrate (PAN) is one of the components of smog. It is a compound of C, H, N, and O. Determine the empirical formula from the following percent composition by mass: 19.8 percent C, 2.50 percent H, 11.6 percent N, 66.1 percent O. What is its molecular formula given that its molar mass is about 120 g?
A) / C2HNO6
B) / C2H3NO5
C) / CH5N2O
D) / C3H6N4O3
35. / The formula for rust can be represented by Fe2O3. How many moles of Fe are present in 24.6 g of the compound?
A) / 2.13 mol
B) / 0.456 mol
C) / 0.154 mol
D) / 0.308 mol
36. / How many grams of sulfur (S) are needed to react completely with 246 g of mercury (Hg) to form HgS?
A) / 39.3 g
B) / 24.6 g
C) / 9.66 103 g
D) / 201 g
37. / Calculate the mass in grams of iodine (I2) that will react completely with 20.4 g of aluminum (Al) to form aluminum iodide (AlI3).
A) / 192 g
B) / 288 g
C) / 61.2 g
D) / 576 g
38. / Tin(II) fluoride (SnF2) is often added to toothpaste as an ingredient to prevent tooth decay. What is the mass of F in grams in 24.6 g of the compound?
A) / 18.6 g
B) / 24.3 g
C) / 5.97 g
D) / 75.7 g
39. / What is the empirical formula of the compound with the following composition?
2.1 percent H, 65.3 percent O, 32.6 percent S.
A) / H2SO4
B) / H2SO3
C) / H2S2O3
D) / HSO3
40. / What is the empirical formula of the compound with the following composition?
40.1 percent C, 6.6 percent H, 53.3 percent O.
A) / CH2O2
B) / CH2O
C) / C2H6O
D) / C2H4O2
41. / Monosodium glutamate (MSG), a food-flavor enhancer, has been blamed for “Chinese restaurant syndrome,” the symptoms of which are headaches and chest pains. MSG has the following composition by mass: 35.51 percent C, 4.77 percent H, 37.85 percent O, 8.29 percent N, and 13.60 percent Na. What is its molecular formula, if its molar mass is about 169 g/mol?
A) / C3H9O4NNa2
B) / C4H6O4N2Na
C) / C5H8O4NNa
D) / C4H4O5NNa
42. / Which of the following equations is balanced?
A) / 2C + O2 CO
B) / 2CO + O2 2CO2
C) / H2 + Br2 HBr
D) / 2K + H2O 2KOH + H2
43. / Which of the following equations is balanced?
A) / 2Mg + O2 2MgO
B) / O3 3O2
C) / 2H2O2 H2O + O2
D) / N2 + 3H2 3NH3
44. / Which of the following equations is balanced?
A) / 2Zn + AgCl 2ZnCl2 + Ag
B) / S8 + 8O2 4SO2
C) / NaOH + 2H2SO4 Na2SO4 + H2O
D) / Cl2 + 2NaI 2NaCl + I2
45. / Which of the following equations is balanced?
A) / 2N2O5 3N2O4 + O2
B) / 2KNO3 2KNO2 + 3O2
C) / NH4NO3 2N2O + 2H2O
D) / NH4NO2 N2 + 2H2O
46. / Which of the following equations is balanced?
A) / 2NaHCO3 Na2CO3 + H2O + CO2
B) / P4O10 + 4H2O 4H3PO4
C) / 2HCl + CaCO3 CaCl2 + 2H2O + CO2
D) / 2Al + 3H2SO4 Al2(SO4)3 + H2
47. / Which of the following equations is balanced?
A) / CO2 + 2KOH K2CO3+ 2H2O
B) / CH4 + 2O2 CO2 + 2H2O
C) / Be2C + H2O 2Be(OH)2 + CH4
D) / Cu + 2HNO3 Cu(NO3)2 + NO + H2O
48. / Consider the combustion of carbon monoxide (CO) in oxygen gas:
2CO(g) + O2(g) 2CO2(g)
Starting with 3.60 moles of CO, calculate the number of moles of CO2 produced if there is enough oxygen gas to react with all of the CO.
A) / 7.20 mol
B) / 44.0 mol
C) / 3.60 mol
D) / 1.80 mol
49. / Silicon tetrachloride (SiCl4) can be prepared by heating Si in chlorine gas:
Si(s) + 2Cl2(g) SiCl4(l)
In one reaction, 0.507 mole of SiCl4 is produced. How many moles of molecular chlorine were used in the reaction?
A) / 2.03 mol
B) / 4.00 mol
C) / 1.01 mol
D) / 0.507 mol
50. / The annual production of sulfur dioxide from burning coal and fossil fuels, auto exhaust, and other sources is about 26 million tons. The equation for the reaction is
S(s) + O2(g) SO2(g)
How much sulfur, present in the original materials, would result in that quantity of SO2?
A) / 2.3 1016 tons
B) / 3.0 1023 tons
C) / 2.6 107 tons
D) / 1.3 107 tons
51. / When baking soda (sodium bicarbonate or sodium hydrogen carbonate, NaHCO3) is heated, it releases carbon dioxide gas, which is responsible for the rising of cookies, donuts, and bread. The balanced equation for this process is:
2NaHCO3 Na2CO3 + H2O + CO2. Calculate the mass of NaHCO3 required to produce 20.5 g of CO2.
A) / 8.38 g
B) / 78.3 g
C) / 157 g
D) / 39.1 g
52. / When potassium cyanide (KCN) reacts with acids, a deadly poisonous gas, hydrogen cyanide (HCN), is given off. Here is the equation:
KCN(aq) + HCl(aq) KCl(aq) + HCN(g)
If a sample of 0.140 g of KCN is treated with an excess of HCl, calculate the amount of HCN formed, in grams.
A) / 0.0581 g
B) / 0.0651 g
C) / 0.0883 g
D) / 0.0270 g
53. / Fermentation is a complex chemical process of wine making in which glucose is converted into ethanol and carbon dioxide:
C6H12O6 2C2H5OH + 2CO2
Starting with 500.4 g of glucose, what is the maximum amount of ethanol in liters that can be obtained by this process? (Density of ethanol = 0.789 g/mL.)
A) / 0.324 L
B) / 0.256 L
C) / 0.202 L
D) / 2.56 L
54. / Each copper(II) sulfate unit is associated with five water molecules in crystalline copper(II) sulfate pentahydrate (CuSO4.5H2O). When this compound is heated in air above 100° C, it loses the water molecules and also its blue color:
CuSO4.5H2O CuSO4 + 5H2O
If 9.60 g of CuSO4 are left after heating 15.01 g of the blue compound, calculate the number of moles of H2O originally present in the compound.
A) / 0.125 mol
B) / 5.38 mol
C) / 0.0600 mol
D) / 0.300 mol
55. / For many years the recovery of gold — that is, the separation of gold from other materials — involved the use of potassium cyanide:
4Au + 8KCN + O2 + 2H2O 4KAu(CN)2 + 4KOH
What is the minimum amount of KCN in moles needed to extract 29.0 g (about an ounce) of gold?
A) / 58.0 mol
B) / 0.294 mol
C) / 0.147 mol
D) / 0.0736 mol
56. / Limestone (CaCO3) is decomposed by heating to quicklime (CaO) and carbon dioxide. Calculate how many grams of quicklime can be produced from 1.0 kg of limestone.
A) / 5.6 102 g
B) / 2.3 102 g
C) / 4.4 102 g
D) / 8.6 102 g
57. / Nitrous oxide (N2O) is also called “laughing gas.” It can be prepared by the thermal decomposition of ammonium nitrate (NH4NO3). The other product is H2O. The balanced equation for this reaction is:
NH4NO3 N2O + 2H2O
How many grams of N2O are formed if 0.46 mole of NH4NO3 is used in the reaction?
A) / 2.0 g
B) / 3.7 101 g
C) / 2.0 101 g
D) / 4.6 10-1 g
58. / The fertilizer ammonium sulfate [(NH4)2SO4] is prepared by the reaction between ammonia (NH3) and sulfuric acid:
2NH3(g) + H2SO4(aq) (NH4)2SO4(aq)
How many kilograms of NH3 are needed to produce 1.00 105 kg of (NH4)2SO4?
A) / 1.70 104 kg
B) / 3.22 103 kg
C) / 2.58 104 kg
D) / 7.42 104 kg
59. / A common laboratory preparation of oxygen gas is the thermal decomposition of potassium chlorate (KClO3). Assuming complete decomposition, calculate the number of grams of O2 gas that can be obtained from 46.0 g of KClO3. (The products are KCl and O2.)
A) / 12.0 g
B) / 18.0 g
C) / 6.00 g
D) / 36.0 g
60. / Nitric oxide (NO) reacts with oxygen gas to form nitrogen dioxide (NO2), a dark-brown gas:
2NO(g) + O2(g) 2NO2(g)
In one experiment 0.886 mole of NO is mixed with 0.503 mole of O2. Calculate the number of moles of NO2 produced (note: first determine which is the limiting reagent).
A) / 0.886 mol
B) / 0.503 mol
C) / 1.01 mol
D) / 1.77 mol
61. / The depletion of ozone (O3) in the stratosphere has been a matter of great concern among scientists in recent years. It is believed that ozone can react with nitric oxide (NO) that is discharged from the high-altitude jet plane, the SST. The reaction is
O3 + NO O2 + NO2
If 0.740 g of O3 reacts with 0.670 g of NO, how many grams of NO2 will be produced?
A) / 1.410 g
B) / 0.670 g
C) / 0.709 g
D) / 0.883 g
62. / Propane (C3H8) is a component of natural gas and is used in domestic cooking and heating. The balanced equation for the combustion of propane is:
C3H8 + 5O2 3CO2 + 4H2O
How many grams of carbon dioxide can be produced by burning 3.65 moles of propane? Assume that oxygen is the excess reagent in this reaction.
A) / 161 g
B) / 11.0 g
C) / 332 g
D) / 482 g
63. / Consider the reaction
MnO2 + 4HCl MnCl2 + Cl2 + 2H2O
If 0.86 mole of MnO2 and 48.2 g of HCl react, how many grams of Cl2 will be produced?
A) / 42.3 g
B) / 93.6 g
C) / 63.4 g
D) / 23.4 g
64. / Hydrogen fluoride is used in the manufacture of Freons (which destroy ozone in the stratosphere) and in the production of aluminum metal. It is prepared by the reaction
CaF2 + H2SO4 CaSO4 + 2HF
In one process 6.00 kg of CaF2 are treated with an excess of H2SO4 and yield 2.86 kg of HF. Calculate the percent yield of HF.
A) / 93.0 %
B) / 95.3 %
C) / 47.6 %
D) / 62.5 %
65. / Nitroglycerin (C3H5N3O9) is a powerful explosive. Its decomposition may be represented by
4C3H5N3O9 6N2 + 12CO2 + 10H2O + O2
This reaction generates a large amount of heat and many gaseous products. It is the sudden formation of these gases, together with their rapid expansion, that produces the explosion. Calculate the percent yield in this reaction if the amount of O2 generated from 2.00 102 g of nitroglycerin is found to be 6.55 g.
A) / 23.2 %
B) / 44.6 %
C) / 92.9 %
D) / 62.5 %
66. / Titanium(IV) oxide (TiO2) is a white substance produced by the action of sulfuric acid on the mineral ilmenite (FeTiO3):
FeTiO3 + H2SO4 TiO2 + FeSO4 + H2O
Its opaque and nontoxic properties make it suitable as a pigment in plastics and paints. In one process 8.00 103 kg of FeTiO3 yielded 3.67 103 kg of TiO2. What is the percent yield of the reaction?
A) / 92.9 %
B) / 62.5 %
C) / 12.3 %
D) / 87.1 %
67. / Ethylene (C2H4), an important industrial organic chemical, can be prepared by heating hexane (C6H14) at 800 °C:
C6H14 C2H4 + other products
If the yield of ethylene production is 42.5 percent, what mass of hexane must be reacted to produce 481 g of ethylene?
A) / 5.56 103 g
B) / 3.47 103 g
C) / 9.95 102 g
D) / 1.13 103 g
68. / Industrially, nitric acid is produced by the Ostwald process represented by the following equations:
4NH3(g) + 5O2(g) 4NO(g) + 6H2O(l)
2NO(g) + O2(g) 2NO2(g)
2NO2(g) + H2O(l) HNO3(aq) + HNO2(aq)
What mass of NH3 (in g) must be used to produce 1.00 ton of HNO3 by the above procedure, assuming an 80 percent yield in each step?(1 ton = 2000 lb; 1 lb = 453.6 g.)
A) / 9.6 105 g
B) / 1.2 106 g
C) / 1.5 106 g
D) / 1.9 106 g
69. / A sample of a compound of Cl and O reacts with an excess of H2 to give 0.233 g of HCl and 0.403 g of H2O. Determine the empirical formula of the compound.
A) / ClO4
B) / Cl2O7
C) / Cl2O5
D) / ClO2
70. / The atomic mass of element X is 33.42 amu. A 27.22-g sample of X combines with 84.10 g of another element Y to form a compound XY. Calculate the atomic mass of Y.
A) / 12.01 amu
B) / 35.45 amu
C) / 68.50 amu
D) / 103.3 amu
71. / How many moles of O are needed to combine with 0.212 mole of C to form CO2?
A) / 0.424 mol
B) / 1.00 mol
C) / 2.00 mol
D) / 0.212 mol
72. / The aluminum sulfate hydrate [Al2(SO4)3 · xH2O] contains 8.20 percent Al by mass. Calculate x, that is, the number of water molecules associated with each Al2(SO4)3 unit.
A) / 2
B) / 5
C) / 18
D) / 9
73. / Mustard gas (C4H8Cl2S) is a poisonous gas that was used in World War I and banned afterward. It causes general destruction of body tissues, resulting in the formation of large water blisters. There is no effective antidote. Calculate the percent composition by mass of the chlorine in mustard gas.
A) / 30.19 %
B) / 44.57 %
C) / 5.069 %
D) / 20.16 %
74. / The carat is the unit of mass used by jewelers. One carat is exactly 200 mg. How many carbon atoms are present in a 24-carat diamond?
A) / 3.0 1023 atoms
B) / 6.0 1023 atoms
C) / 2.4 1023 atoms
D) / 4.8 1023 atoms
75. / An iron bar weighed 664 g. After the bar had been standing in moist air for a month, exactly one-eighth of the iron turned to rust (Fe2O3). Calculate the final mass of the rust.
A) / 83.0 g
B) / 107 g
C) / 209 g
D) / 119 g
76. / A certain metal oxide has the formula MO where M denotes the metal. A 39.46-g sample of the compound is strongly heated in an atmosphere of hydrogen to remove oxygen as water molecules. At the end, 31.70 g of the metal is left over. If O has an atomic mass of 16.00 amu, calculate the atomic mass of M and identify the element.
A) / 58.7 amu; Ni
B) / 63.5 amu; Cu
C) / 65.4 amu; Zn
D) / 58.9 amu; Co
77. / An impure sample of zinc (Zn) is treated with an excess of sulfuric acid (H2SO4) to form zinc sulfate (ZnSO4) and molecular hydrogen (H2). If 0.0764 g of H2 is obtained from 3.86 g of the sample, calculate the percent purity of the sample.
A) / 88.9 %
B) / 64.2 %
C) / 48.5 %
D) / 92.9 %
78. / One of the reactions that occurs in a blast furnace, where iron ore is converted to cast iron, is
Fe2O3 + 3CO 2Fe + 3CO2
Suppose that 1.64 103 kg of Fe are obtained from a 2.62 103 kg sample of Fe2O3. Assuming that the reaction goes to completion, what is the percent purity of Fe2O3 in the original sample?
A) / 89.6 %
B) / 44.8 %
C) / 32.5 %
D) / 95.4 %
79. / Carbon dioxide (CO2) is the gas that is mainly responsible for global warming (the greenhouse effect). The burning of fossil fuels is a major cause of the increased concentration of CO2 in the atmosphere. Carbon dioxide is also the end product of metabolism. The general overall equation of glucose degradation is C6H12O6 + 6O2 6CO2 + 6H2O. Using glucose as an example of food, calculate the annual human production of CO2 in grams, assuming that each person consumes 5.0 102 g of glucose per day. The world's population is 6.5 billion, and there are 365 days in a year.
A) / 1.2 1015 g/yr
B) / 3.5 1015 g/yr
C) / 1.7 1015 g/yr
D) / 4.6 1015 g/yr
80. / Carbohydrates are compounds containing carbon, hydrogen, and oxygen in which the hydrogen to oxygen ratio is 2:1. A certain carbohydrate contains 40.0 percent carbon by mass. Calculate the empirical and molecular formulas of the compound if the approximate molar mass is 178 g.
A) / C2H6O3; C4H12O6
B) / CH2O; C6H12O6
C) / C4H6O3; C8H12O6
D) / CH2O; C12H24O12
81. / Analysis of a metal chloride XCl3 shows that it contains 67.2 percent Cl by mass. Calculate the molar mass of X and identify the element.
A) / 55.9 g/mol; Fe
B) / 96.0 g/mol; Mo
C) / 63.6 g/mol; Cu
D) / 51.9 g/mol; Cr
82. / Hemoglobin (C2952H4664N812O832S8Fe4) is the oxygen carrier in blood. Begin by calculating its molar mass. An average adult has about 5.0 L of blood. Every milliliter of blood has approximately 5.0 109 erythrocytes, or red blood cells, and every red blood cell has about 2.8 108 hemoglobin molecules. Calculate the mass of hemoglobin molecules in grams in an average adult.
A) / 7.6 102 g
B) / 4.3 102 g
C) / 2.7 10-6 g
D) / 7.6 10-2 g
83. / Myoglobin stores oxygen for metabolic processes in muscle. Chemical analysis shows that it contains 0.34 percent Fe by mass. What is the molar mass of myoglobin? (There is one Fe atom per molecule.)
A) / 2.9 102 g/mol
B) / 1.6 104 g/mol
C) / 4.3 103 g/mol
D) / 6.2 104 g/mol
84. / Calculate the number of cations and anions in 8.38 g of KBr.
A) / 4.24 1022 K+; 4.24 1022 Br-
B) / 1.29 1023 K+; 4.24 1022 Br-
C) / 1.29 1023 K+; 6.31 1022 Br-
D) / 4.24 1022 K+; 6.31 1022 Br-
85. / A sample containing NaCl, Na2SO4, and NaNO3 gives the following elemental analysis: Na: 32.08 percent; O: 36.01 percent; Cl: 19.51 percent. Calculate the mass percent of NaCl in the sample.
A) / 36.01 %
B) / 19.51 %
C) / 45.63 %
D) / 32.17 %
86. / Calculate the percent composition by mass of phosphorus (P) in calcium phosphate [Ca3(PO4)2], a major component of bone.
A) / 15.38 %
B) / 19.97 %
C) / 22.96 %
D) / 33.29 %
87. / Lysine, an essential amino acid in the human body, contains C, H, O, and N. In one experiment, the complete combustion of 2.175 g of lysine gave 3.94 g CO2 and 1.89 g H2O. In a separate experiment, 1.873 g of lysine gave 0.436 g NH3. The approximate molar mass of lysine is 150 g. What is the molecular formula of the compound?
A) / C5H12N3O2
B) / C5H10N2O3
C) / C6H14N2O2
D) / C7H16NO2
88. / The natural abundances of the two stable isotopes of hydrogen (hydrogen and deuterium) are 11H: 99.985 percent and 21H: 0.015 percent. Assume that water exists as either H2O or D2O. Calculate the number of D2O molecules in exactly 400 mL of water. (Density = 1.00 g/mL.)
A) / 4.63 1021 molecules
B) / 3.34 1022 molecules
C) / 6.00 1023 molecules
D) / 2.01 1021 molecules
89. / A compound containing only C, H, and Cl was examined in a mass spectrometer. The highest mass peak seen corresponds to an ion mass of 52 amu. The most abundant mass peak seen corresponds to an ion mass of 50 amu and is about three times as intense as the peak at 52 amu. Deduce a reasonable molecular formula for the compound. (Hint: Chlorine is the only element that has isotopes in comparable abundances: 35Cl: 75.5 percent; 37Cl: 24.5 percent. For H, use 1H; for C, use 12C.)
A) / C2H5Cl
B) / CH2Cl2
C) / CH3Cl
D) / C2H4Cl2
90. / In the formation of carbon monoxide, CO, it is found that 2.445 g of carbon combine with 3.257 g of oxygen. What is the atomic mass of oxygen if the atomic mass of carbon is 12.01 amu?
A) / 16.01 amu
B) / 16.00 amu
C) / 15.98 amu
D) / 15.99 amu
91. / What mole ratio of molecular chlorine (Cl2) to molecular oxygen (O2) would result from the breakup of the compound Cl2O7 into its constituent elements?
A) / 1:3.5
B) / 3.5:1
C) / 2:1
D) / 1:3
92. / Which of the following substances contains the greatest mass of chlorine?
A) / 5.0 g Cl2
B) / 60.0 g NaClO3
C) / 0.10 mol KCl
D) / 0.50 mol Cl2
93. / Potash is any potassium mineral that is used for its potassium content. Most of the potash produced in the United States goes into fertilizer. The major sources of potash are potassium chloride (KCl) and potassium sulfate (K2SO4). Potash production is often reported as the potassium oxide (K2O) equivalent or the amount of K2O that could be made from a given mineral. If KCl costs $0.055 per kg, for what price (dollar per kg) must K2SO4 be sold in order to supply the same amount of potassium on a per dollar basis?
A) / $0.033/kg
B) / $0.11/kg
C) / $0.047/kg
D) / $0.0023/kg
94. / Platinum forms a compound with chlorine, which contains 26.7 percent Cl by mass. Determine the empirical formula of the compound.
A) / PtCl3
B) / PtCl2
C) / PtCl
D) / Pt2Cl3
95. / The formula of a hydrate of barium chloride is BaCl2 ·xH2O. If 1.936 g of the compound gives 1.864 g of anhydrous BaSO4 upon treatment with sulfuric acid, calculate the value of x.
A) / 2
B) / 3
C) / 5
D) / 1
96. / It is estimated that the day Mt. St. Helens erupted (May 18, 1980), about 4.0 105 tons of SO2 were released into the atmosphere. If all the SO2 were eventually converted to sulfuric acid, how many tons of H2SO4 were produced?
A) / 3.1 105 tons
B) / 6.1 105 tons
C) / 2.0 105 tons
D) / 4.0 105 tons
97. / A mixture of CuSO4 · 5H2O and MgSO4 · 7H2O is heated until all the water is lost. If 5.020 g of the mixture gives 2.988 g of the anhydrous salts, what is the percent by mass of CuSO4 · 5H2O in the mixture?
A) / 66.33 %
B) / 70.86 %
C) / 22.90 %
D) / 55.67 %
98. / When 0.273 g of Mg is heated strongly in a nitrogen (N2) atmosphere, a chemical reaction occurs. The product of the reaction weighs 0.378 g. Calculate the empirical formula of the compound containing Mg and N.
A) / MgN
B) / Mg2N
C) / MgN2
D) / Mg3N2
99. / A mixture of methane (CH4) and ethane (C2H6) of mass 13.43 g is completely burned in oxygen. If the total mass of CO2 and H2O produced is 64.84 g, calculate the fraction of CH4 in the mixture.
A) / 0.613
B) / 0.295
C) / 0.387
D) / 0.833
100. / Leaded gasoline contains an additive to prevent engine “knocking.” On analysis, the additive compound is found to contain carbon, hydrogen, and lead (Pb) (hence, “leaded gasoline”). When 51.36 g of this compound are burned in an apparatus such as that shown in Figure 3.5, 55.90 g of CO2 and 28.61 g of H2O are produced. Determine the empirical formula of the gasoline additive.
A) / PbC4H12
B) / PbC4H10
C) / PbC8H20
D) / PbC2H6
101. / Because of its detrimental effect on the environment, the lead compound described in Problem 136 has been replaced in recent years by methyl tert-butyl ether (a compound of C, H, and O) to enhance the performance of gasoline. (As of 1999, this compound is also being phased out because of its contamination of drinking water.) When 12.1 g of the compound are burned in an apparatus like the one shown in Figure 3.5, 30.2 g of CO2 and 14.8 g of H2O are formed. What is the empirical formula of the compound?
A) / C5H12O
B) / CH2O
C) / C8H8O
D) / C3H6O
102. / Suppose you are given a cube made of magnesium (Mg) metal of edge length 1.0 cm. Calculate the number of Mg atoms in the cube. The density of Mg is 1.74 g/cm3.
A) / 1.0 1024 atoms
B) / 6.0 1023 atoms
C) / 1.7 1023 atoms
D) / 4.3 1022 atoms
103. / A certain sample of coal contains 1.6 percent sulfur by mass. When the coal is burned, the sulfur is converted to sulfur dioxide. To prevent air pollution, this sulfur dioxide is treated with calcium oxide (CaO) to form calcium sulfite (CaSO3). Calculate the daily mass (in kilograms) of CaO needed by a power plant that uses 6.60 106 kg of coal per day.
A) / 6.42 105 kg
B) / 1.06 105 kg
C) / 1.85 105 kg
D) / 4.35 106 kg
104. / Air is a mixture of many gases. However, in calculating its “molar mass” we need consider only the three major components: nitrogen, oxygen, and argon. Given that one mole of air at sea level is made up of 78.08 percent nitrogen, 20.95 percent oxygen, and 0.97 percent argon, what is the molar mass of air?
A) / 55.55 g/mol
B) / 28.97 g/mol
C) / 99.97 g/mol
D) / 14.68 g/mol
105. / A die has an edge length of 1.5 cm. What is the volume of one mole of such dice?
A) / 2.0 1024 cm3
B) / 3.4 1023 cm3
C) / 6.0 1023 cm3
D) / 8.8 1023 cm3
106. / The following is a crude but effective method for estimating the order of magnitude of Avogadro's number using stearic acid (C18H36O2). When stearic acid is added to water, its molecules collect at the surface and form a monolayer; that is, the layer is only one molecule thick. The cross-sectional area of each stearic acid molecule has been measured to be 0.21 nm2. In one experiment it is found that 1.4 10 -4 g of stearic acid is needed to form a monolayer over water in a dish of diameter 20 cm. Based on these measurements, what is Avogadro's number? (The area of a circle of radius r is r2.)
A) / 2.0 1023
B) / 5.5 1023
C) / 3.1 1023
D) / 6.0 1023
107. / Octane (C8H18) is a component of gasoline. Complete combustion of octane yields CO2 and H2O. Incomplete combustion produces CO and H2O, which not only reduces the efficiency of the engine using the fuel but is also toxic. In a certain test run, 1.000 gallon of octane is burned in an engine. The total mass of CO, CO2, and H2O produced is 11.53 kg. Calculate the efficiency of the process; that is, calculate the fraction of octane converted to CO2. The density of octane is 2.650 kg/gallon.
A) / 86.49 %
B) / 75.56 %
C) / 92.20 %
D) / 44.23 %
108. / Industrially, hydrogen gas can be prepared by reacting propane gas (C3H8) with steam at about 400°C. The products are carbon monoxide (CO) and hydrogen gas (H2). How many kilograms of H2 can be obtained from 2.84 103 kg of propane?
A) / 1.30 102 kg
B) / 4.55 102 kg
C) / 1.09 103 kg
D) / 9.09 102 kg
109. / Avogadro's number represents the number of grams in a mole of a substance.
A) / True
B) / False
110. / Grams/mol are the commonly used units for molar mass.
A) / True
B) / False
111. / There are more atoms in 1.10 g of hydrogen atoms than there are in 14.7 g of chromium atoms.
A) / True
B) / False
112. / 5.1 10-23 mole of helium has a greater mass than two atoms of lead.
A) / True
B) / False
113. / The percent composition by mass of N in ammonia (NH3) is 82.24%.
A) / True
B) / False
114. / The word “empirical” in empirical formula means “calculated.”
A) / True
B) / False
115. / If we know the empirical formula of a compound, we need no additional information to determine its molecular formula.
A) / True
B) / False
116. / The molar mass of caffeine is 194.19 g and the empirical formula is C4H5N2O; therefore the molecular formula of caffeine is C8H10N4O2.
A) / True
B) / False
117. / A reactant is produced by a chemical reaction.
A) / True
B) / False
118. / A chemical equation uses chemical symbols to show what happens during a chemical reaction.
A) / True
B) / False
119. / The law of conservation of mass is obeyed by a balanced equation.
A) / True
B) / False
120. / The reactant used up first in a chemical reaction is called the excess reagent.
A) / True
B) / False
121. / The yield of a reaction is determined only by the amount of the limiting reagent.
A) / True
B) / False
122. / 0.72 g of O2 has a greater mass than 0.0011 mol of chlorophyll (C55H72MgN4O5).
A) / True
B) / False
123. / 1 g of hydrogen molecules contains as many H atoms as 1 g of hydrogen atoms.
A) / True
B) / False
Answer Key