Ch 3 Practice Problems
1.
2.
Bromine exists naturally as a mixture of bromine-79 and bromine-81 isotopes. An atom of bromine-79 contains
A) 35 protons, 44 neutrons, and 35 electrons.
B) 34 protons and 35 electrons only.
C) 44 protons, 44 electrons, and 35 neutrons.
D) 35 protons, 79 neutrons, and 35 electrons.
E)
79 protons, 79 electrons, and 35 neutrons.
The atomic mass of rhenium is 186.2. Given that 37.1% of natural rhenium is rhenium-185, what is the other stable isotope?
183
A)
75 Re
B)
187
75
Re
C)
189
75
Re
D)
181
75
Re
190
75
3.
4.
5.
6.
7.
8.
E)
Re
Consider the new element moonium, atomic number 118, atomic mass 273.2 g. The nucleus of an atom of moonium-273
contains
A) 118 protons, 155 neutrons, 118 electrons.
B) 118 protons, 118 neutrons.
C) 118 protons, 118 alpha particles.
D) 118 protons, 155 neutrons.
E)
118 protons, 273 neutrons.
For a new element, 67.16% is an isotope with mass 280.8 amu, 2.76% is an isotope with mass 283.7 amu, and 30.08% is an
isotope with mass 284.8 amu. Calculate the average atomic mass of this new element.
A) 282.1 amu
B) 283.1 amu
C) 313.4 amu
D) 280.8 amu
E)
849.3 amu
The average mass of a boron atom is 10.81. If you were able to isolate a single boron atom, what is the chance that you would
randomly get an atom with mass 10.81?
A) 0%
B) 0.81%
C) about 11%
D) 10.81%
E)
greater than 50%
Indium has atomic number 49 and atomic mass 114.8 g. Naturally occurring indium contains a mixture of indium-112 and
indium-115 in an atomic ratio of approximately
A) 6/94.
B) 25/75.
C) 50/50.
D) 75/25.
E)
94/6.
Boron naturally occurs in two isotopic forms. The more common isotope is 11B (atomic mass 11.01 amu), which is 80.00%
abundant. The average atomic mass of boron is 10.81. What is the mass of the other isotope?
A) 10.91 amu.
B) 10.01 amu.
C) 11.00 amu.
D) 11.01 amu.
E)
10.81 amu.
A sample of iron weighing 16.8 g contains how many moles of iron atoms?
A) 0.0874 moles
B) 0.301 moles
C) 0.646 moles
D) 0.132 moles
E)
3.32 moles
9.
10.
11.
12.
13.
14.
15.
16.
17.
A single atom of an element weighs 5.81  10–23 g. Identify the isotope.
A) 80Br
B) 35Cl
C) 103Rh
D) 45Sc
E)
none of these
Iron is biologically important in the transport of oxygen by red blood cells from the lungs to the various organs of the body. In
the blood of an adult human, there are approximately 2.60  1013 red blood cells with a total of 2.90 g of iron. On the average,
how many iron atoms are present in each red blood cell? (molar mass for Fe = 55.85 g)
A) 8.33  10–10
B) 1.20  109
C) 3.12  1022
D) 2.60  1013
E)
5.19  10–2
An alkali metal oxide contains 83.01% metal by mass. Determine the identity of the metal.
A) Cs
B) K
C) Li
D) Na
E)
Rb
What is the molar mass of ethanol (C2H5OH)?
A) 45.07
B) 38.90
C) 46.07
D) 34.17
E)
62.07
For which of the following compounds does 1.0 g represent 5.55  10-2 mol?
A) NO2
B) H2O
C) C2H6
D) NH3
E)
CO
Which compound has the smallest molar mass?
A) C2H4O
B) CO2
C) CH3Cl
D) C2H6
E)
none of these
For which compound does 0.256 mole weigh 12.9 g?
A) C2H4O
B) CO2
C) CH3Cl
D) C2H6
E)
C2H4O2
Calculate the molar mass of a sample if a single molecule weighs 5.34  10-23 g.
A) 1.13  1046 g/mol
B) 12.0 g/mol
C) 5.34  10-23 g/mol
D) 32.2 g/mol
E)
none of these
How many moles of P4 molecules are in 140.1 g of phosphorus?
A) 4.524 mol
B) 1.736  104 mol
C) 1.131 mol
D) 2.326  101 mol
E)
1.401  101 mol
18.
19.
20.
21.
22.
23.
24.
25.
26.
What is the mass (in grams) of one molecule of phosphorus pentachloride?
A) 1.10  10-22 g
B) 3.46  10-22 g
C) 1.00 g
D) 208.22 g
E)
1.25  1026 g
How many molecules of ammonia are present in 3.7 g of ammonia?
A) 2.2  101
B) 2.2  1024
C) 3.6  10-25
D) 1.3  1023
E)
4.5  1023
How many atoms of hydrogen are present in 4.0 g of ammonia?
A) 4.2  1023
B) 7.8  1024
C) 1.2  10-24
D) 1.8 1024
E)
0.70
The mass of 0.82 mol of a diatomic molecule is 131.3 g. Identify the molecule.
A) F2
B) Cl2
C) Br2
D) I2
E)
Xe
Roundup, an herbicide manufactured by Monsanto, has the formula C 3H8NO5P. How many moles of molecules are there in a
500.-g sample of Roundup?
A) 0.338
B) 1.75
C) 2.96
D) 84.5
E)
none of these
What mass of styrene (molar mass 104.1 g/mol) contains 4.50  1020 molecules of styrene?
A) 7.48  10-4 g
B) 7.48  10-3 g
C) 7.78  10-2 g
D) 0.00778 g
E)
7.48  104 g
Phosphorus has the molecular formula P 4 and sulfur has the molecular formula S8. How many grams of phosphorus contain the
same number of molecules as 6.41 g of sulfur?
A) 3.10 g
B) 3.21 g
C) 6.19 g
D) 6.41 g
E)
none of these
The molar mass of the insecticide dibromoethane is 187.9 g/mol. Its molecular formula is C 2H4Br2. How many atoms of carbon
are in a sample of dibromoethane weighing 1.879 g?
A) none of these
B) 6.022  1021
C) 6.022  100.21
D) 12.04  1044
E)
1.204  1022
A given sample of xenon fluoride contains molecules of a single type, XeF n, where n is some whole number. Given that 9.03 
1020 molecules of XeFn weigh 0.311 g, calculate n.
A) 1
B) 2
C) 4
D) none of these
27.
28.
29.
30.
31.
32.
33.
34.
35.
NaHCO3 is the active ingredient in baking soda. How many grams of oxygen are in 0.44 g of NaHCO 3?
A) 0.016 g
B) 1.3 g
C) 0.084 g
D) 0.0052 g
E)
0.25 g
The empirical formula of sugar is CH2O and its molar mass is 180.2 g/mole. If one teaspoon of sugar weighs 3.50 g, how many
moles of sugar and how many molecules of sugar are present?
A) 0.117 mole, 7.03  1022 molecules
B) 0.0194 mole, 3.24  1026 molecules
C) 0.0194 mole, 1.17  1022 molecules
D) 0.0583 mole, 3.51  1022 molecules
E)
0.0295 mole, 1.78  1022 molecules
Compound X2Y is 60% X by mass. Calculate the percent Y by mass of the compound X 2Y2.
A) 20%
B) 30%
C) 40%
D) 60%
E)
80%
Cortisone consists of molecules, each of which contains 21 atoms of carbon (plus other atoms). The mass percentage of carbon
in cortisone is 69.98%. What is the molar mass of cortisone?
A) 176.5 g/mol
B) 252.2 g/mol
C) 287.6 g/mol
D) 312.8 g/mol
E)
360.4 g/mol
An oxybromate compound, NaBrOx, where x is a whole number, is analyzed and found to contain 52.95% Br by mass. What is
x?
A) 0
B) 1
C) 2
D) 3
E)
4
Which of the following contains the greatest percentage of nitrogen by mass?
A) NH3
B) NO2
C) N2O
D) C6H4N3O6
E)
HCN
The molar mass of the insecticide dibromoethane is 187.9. Its molecular formula is C 2H4Br2. What percent by mass of bromine
does dibromoethane contain?
A) 37.8%
B) 42.5%
C) 50.0%
D) 85.0%
E)
89.3%
A substance contains 3.024 g hydrogen, 30.97 g phosphorus, and 64.00 g oxygen. How many grams of oxygen are in an 85.00g sample of the substance?
A) 16.00 g
B) 55.51 g
C) 64.00 g
D) 130.1 g
E)
none of these
What is the percent by mass of hydrogen in ammonium acetate?
A) 5.23%
B) 3.92%
C) 9.15%
D) 14.3%
E)
7.07%
36.
37.
38.
39.
40.
41.
42.
43.
44.
A hydrate of copper(II) sulfate is 25.5% copper by mass. How many water molecules are there for each unit of copper(II)
sulfate?
A) 1
B) 2
C) 3
D) 4
E)
5
Which of the following compounds has the same percent composition by mass as styrene, C8H8?
A) acetylene, C2H2
B) benzene, C6H6
C) cyclobutadiene, C4H4
D) -ethyl naphthalene, C12H12
E)
all of these
Find the percent sulfur (atoms) by mass in sodium sulfide.
A) 41.1%
B) 58.2%
C) 73.6%
D) 52.1%
E)
74.4%
You find a compound composed only of element X and hydrogen, and you know that it is 91.33% element X by mass. Each
molecule has 2.67 times as many H atoms as X atoms. What is element X?
A) C
B) Ne
C) Si
D) Cl
E)
Cu
A mixture of NaCl and NaNO3 is 31.7% sodium by mass. What is the approximate percent of NaCl in this mixture?
A) 30%
B) 32%
C) 34%
D) 36%
E)
38%
TNT consists of carbon, nitrogen, oxygen, and hydrogen. It is 37.02% carbon by mass, 18.49% nitrogen by mass, and 42.27%
oxygen by mass. The molar mass of TNT is between 210 g/mol and 245 g/mol. What is the molecular formula for TNT?
A) C7H5N3O6
B) C4H7N6O6
C) C8H12N3O4
D) C6H4N3O6
E)
none of these
Caffeine consists of carbon, hydrogen, oxygen, and nitrogen. When 0.1920 g of caffeine is burned in an excess of oxygen,
0.3482 g of carbon dioxide and 0.0891 g water are formed. Caffeine is 28.84% nitrogen by mass. Its molar mass is between
190 and 200 g/mol. What is the formula for caffeine?
A) C4H5N2O
B) C3H2N2O2
C) C6H4N4O4
D) C8H10N4O2
E)
none of these
The empirical formula of a group of compounds is CHCl. Lindane, a powerful insecticide, is a member of this group. The molar
mass of lindane is 290.8. How many atoms of carbon does a molecule of lindane contain?
A) 2
B) 3
C) 4
D) 6
E)
8
The empirical formula of styrene is CH; its molar mass is 104.1. What is the molecular formula of styrene?
A) C2H4
B) C8H8
C) C10H12
D) C6H6
45.
46.
47.
48.
49.
50.
51.
52.
What is the empirical formula of a hydrocarbon (a compound that consists of only carbon and hydrogen) that contains 81.7%
carbon by mass?
A) C2H6
B) C3H8
C) C4H10
D) C5H12
E)
none of these
The mass percent of iron in an iron oxide is 77.7%. Find the empirical formula.
A) Fe3O2
B) Fe3O4
C) Fe2O3
D) FeO
E)
none of these
Adipic acid contains 49.32% C, 43.84% O, and 6.85% H by mass. What is the empirical formula?
A) C3H5O2
B) C3H3O4
C) C2HO3
D) C2H5O4
E)
C3HO3
Vitamin C contains the elements C, H, and O. It is known to contain 40.9% C and 4.58% H by mass. The molar mass of vitamin
C has been found to be about 180. The molecular formula for vitamin C is
A) C2H3O2
B) C3H4O3
C) C4H6O4
D) C6H8O6
E)
none of these
A 2.00-g sample of an oxide of bromine is converted to 2.936 g of AgBr. Calculate the empirical formula of the oxide. (molar
mass for AgBr = 187.78)
A) BrO3
B) BrO2
C) BrO
D) Br2O
E)
none of these
A 0.4647-g sample of a compound known to contain only carbon, hydrogen, and oxygen was burned in oxygen to yield 0.8635
g of CO2 and 0.1767 g of H2O. What is the empirical formula of the compound?
A) CHO
B) C2H2O
C) C3H3O2
D) C6H3O2
E)
C3H6O2
When the equation C10H22 + O2  CO2 + H2O is balanced with the smallest set of integers, the sum of the coefficients is
A) 4
B) 64
C) 75
D) 44
E)
53
Consider the following unbalanced equation:
C4H10 + O2  CO2 + H2O
For every 1.0 mol of C4H10, ___ mol of O2 is required.
A) 1.0
B) 6.5
C) 8.0
D) 13.0
E)
none of these
53.
54.
55.
56.
57.
58.
59.
60.
wPCl5 + xH2O  yPOCl3 + zHCl
When the equation is properly balanced, what are the coefficients?
A) w = 1, x = 2, y = 2, z = 4
B) w = 2, x = 2, y = 2, z = 2
C) w = 2, x = 2, y = 2, z = 4
D) w = 1, x = 1, y = 1, z = 2
E) none of these
What is the subscript of aluminum in the formula of aluminum phosphate?
A) 1
B) 2
C) 3
D) 4
E)
0
Give (in order) the correct coefficients to balance the following reaction:
H2SnCl6 + H2S  SnS2 + HCl
A) 1, 2, 1, 6
B) 1, 2, 2, 2
C) 1, 1, 1, 6
D) 6, 2, 1, 1
E)
2, 4, 2, 6
In the balanced equation for the reaction
[A]P4O6(s) + [B]H2O(l)  [C]H3PO3(aq)
if [A] equals 2, the coefficient [C] equals
A) 2
B) 4
C) 6
D) 10
E)
none of these
Which of the following equations correctly describes the combustion of CH 4 and O2 to produce water (H2O) and carbon dioxide
(CO2)?
A) CH4 + (1/2)O2  CO2 + H2O
B) CH4 + O2  CO2 + 2H2O
C) CH4 + 2O2  CO2 + 2H2O
D) CH4 + 3O2  2CO2 + H2O
When the following equation is balanced, what is the sum of the coefficients?
Al2(SO4)3 + Ca(OH)2  Al(OH)3 + CaSO4
A) 4
B) 9
C) 8
D) 3
E) 10
When the equation FeCr2O4 + K2CO3 + O2  K2CrO4 + Fe2O3 + CO2 is balanced with the smallest set of integers, the sum of
the coefficients is
A) 6
B) 9
C) 15
D) 24
E) 37
Potassium forms an oxide containing 1 oxygen atom for every 2 atoms of potassium. What is the coefficient of oxygen in the
balanced equation for the reaction of potassium with oxygen to form this oxide?
A) 0
B) 1
C) 2
D) 3
E) 4
61.
62.
63.
64.
65.
66.
67.
How many moles of sodium phosphate are required to react completely with 4.6 mol of calcium nitrate to form sodium nitrate
and calcium phosphate?
A) 6.9 mol
B) 4.6 mol
C) 3.1 mol
D) 2.3 mol
E)
1.5 mol
When the equation NH3 + O2  NO + H2O is balanced with the smallest set of integers, the sum of the coefficients is
A) 4
B) 12
C) 14
D) 19
E)
24
Indium reacts with chlorine to form InCl3. In the balanced equation for this reaction, the coefficient of the indium trichloride is
A) 1
B) 2
C) 3
D) 4
E)
6
Consider the following unbalanced equation:
KO2 + H2O  KOH + O2 + H2O2
For every 3.0 mol of KO2, ___ mol of H2O is needed for a complete reaction.
A) 1.0
B) 2.0
C) 3.0
D) 6.0
E)
none of these
Baking powder, a mixture of cream of tartar (KHC4H4O6, molar mass 188 g/mol) and baking soda (NaHCO3, molar mass 84.0
g/mol), undergoes the following reaction at baking temperatures:
KHC4H4O6 + NaHCO3  KNaC4H4O6 +H2O + CO2
(The CO2 makes the cake rise.) A recipe calls for two level teaspoons (a total of 8.0 g) of cream of tartar. How much baking
soda must be added for both materials to react completely?
A) 0.45 g
B) 3.6 g
C) 18 g
D) 8.0 g
E)
none of these
A reaction occurs between sodium carbonate and hydrochloric acid producing sodium chloride, carbon dioxide, and water. The
correct set of coefficients, respectively, for the balanced reaction is
A) 3, 6, 6, 3, 4.
B) 8, 6, 5, 10, 5.
C) 5, 10, 10, 5, 5.
D) 1, 2, 2, 1, 1.
E)
none of these
A 6.32-g sample of potassium chlorate was decomposed according to the following equation:
2KClO3  2KCl + 3O2
How many moles of oxygen are formed?
A) 1.65 mol
B) 0.051 mol
C) 0.0344 mol
D) 0.0774 mol
E)
none of these
68.
Sulfuric acid may be produced by the following process:
4FeS2 + 11O2  2Fe2O3 + 8SO2
2SO2 + O2  2SO3
SO3 + H2O  H2SO4
69.
70.
71.
72.
How many moles of H2SO4 will be produced form 5.00 mol of FeS2?
A) 6.11 mol
B) 5.00 mol
C) 10.0 mol
D) 12.2 mol
E)
20.0 mol
Consider the following reaction:
CH4(g) + 4Cl2(g)  CCl4(g) + 4HCl(g)
What mass of CCl4 is formed by the reaction of 8.00 g of methane with an excess of chlorine?
A) 1.42 g
B) 7.10 g
C) 14.2 g
D) 76.7 g
E)
none of these
When rubidium metal is exposed to air, one atom of rubidium, Rb, combines with two atoms of oxygen. If 1.75 g of rubidium is
exposed to air, what will be the mass of the product in grams?
A) 0.328 g
B) 0.655 g
C) 1.37 g
D) 2.08 g
E)
2.41 g
Iron is produced from its ore by the following reactions:
2C(s) + O2(g)  2CO(g)
Fe2O3(s) + 3CO(g)  2Fe(s) + 3CO2(g)
How many moles of O2(g) are needed to produce 2.4 mol Fe(s)?
A) 1.2 mol O2
B) 1.8 mol O2
C) 4.0 mol O2
D) 3.6 mol O2
Consider the following two reactions.
Mg + 2HCl  MgCl2 + H2
2H2 + O2  2H2O
73.
How much water (in grams) is produced from 10.0 g of Mg?
A) 1.85 g
B) 3.71 g
C) 7.41 g
D) 18.0 g
E)
none of these
The refining of aluminum from bauxite ore (which contains 50.% Al 2O3 by mass) proceeds by the overall reaction 2Al2O3 + 3C
 4Al + 3CO2. How much bauxite ore is required to give the 5.0  1013 g of aluminum produced each year in the United States?
(Assume 100% conversion.)
A) 1.3  1013 g
B) 5.3  1013 g
C) 1.9  1014 g
D) 7.6  1014 g
74.
75.
76.
77.
78.
79.
80.
One commercial system removes SO2 emissions from smoke at 95.0°C by the following set of balanced reactions:
SO2(g) + Cl2  SO2Cl2(g)
SO2Cl2 + 2H2O  H2SO4 + 2HCl
H2SO4 + Ca(OH)2  CaSO4(s) + 2H2O
Assuming the process is 95.0% efficient, how many grams of CaSO 4 may be produced from 1.00  102 g of SO2 (molar masses:
SO2, 64.1 g/mol; CaSO4, 136 g/mol)?
A) 44.8 g
B) 47.1 g
C) 87.2 g
D) 202 g
E)
212 g
How many grams of Ca(NO3)2 can be produced by reacting excess HNO3 with 7.40 g of Ca(OH)2?
A) 10.2 g
B) 16.4 g
C) 32.8 g
D) 8.22 g
E)
7.40 g
How many grams of H2O will be formed when 36.8 g H2 is mixed with 40.2 g O2 and allowed to completely react to form
water?
A) 45.2 g
B) 77.0 g
C) 22.6 g
D) 331 g
E)
51.3 g
The limiting reactant in a reaction
A) has the lowest coefficient in a balanced equation.
B) is the reactant for which you have the least number of moles.
C) has the lowest ratio of moles available to coefficient in the balanced equation.
D) has the lowest ratio of coefficient in the balanced equation to moles available.
E)
none of these
28.6 g of Al and 17.8 g of Br2 react according to the following equation:
2Al + 3Br2  2AlBr3
What mass of AlBr3 is formed, assuming 100% yield?
A) 283 g
B) 19.8 g
C) 29.7 g
D) 44.6 g
E)
46.4 g
In the reaction
2A + 3B  C
4.0 mol A react with 4.0 mol B. Which reactant is limiting?
A) Neither is limiting because equal amounts (4.0 mol) of each reactant are used.
B) A is limiting because 2 is smaller than 3 (the coefficients in the balanced equation).
C) A is limiting because there are 2 mol of it but 4.0 mol are needed.
D) B is limiting because 3 is larger than 2 (the coefficients in the balanced equation).
E)
B is limiting because there are 4.0 mol of it but 6.0 mol are needed.
A 9.22-g sample of AgNO3 is reacted with BaCl2 according to the equation
2AgNO3(aq) + BaCl2(aq)  2AgCl(s) + Ba(NO3)2(aq)
to give 4.86 g of AgCl. What is the percent yield of AgCl?
A) 44.5%
B) 52.7%
C) 31.2%
D) 62.5%
E) 18.7%
81.
82.
83.
84.
85.
86.
87.
When 10.0 g of hydrogen gas reacts with 10.0 g of oxygen gas to form water, what is the theoretical yield of water?
A) 10.0 g
B) 10.6 g
C) 11.3 g
D) 20.0 g
E)
89.4 g
Consider the following reaction:
CH4(g) + 4Cl2(g)  CCl4(g) + 4HCl(g)
What mass of CCl4 will be formed if 1.2 moles of methane react with 1.6 moles of chlorine?
A) 18.5 g
B) 246 g
C) 984 g
D) 61.5 g
E)
58.3 g
In the reaction
2A + B  3C + D
3.0 mol A and 2.0 mol B react to form 4.0 mol C. What is the percent yield of this reaction?
A) 50%
B) 67%
C) 75%
D) 89%
E)
100%
SO2 reacts with H2S as follows:
2H2S + SO2  3S + 2H2O
When 7.50 g of H2S reacts with 12.75 g of SO2, which statement applies?
A) 6.38 g of sulfur is formed.
B) 10.6 g of sulfur is formed.
C) 0.0216 mol of H2S remains.
D) 1.13 g of H2S remains.
E)
SO2 is the limiting reagent.
A 15-g sample of lithium is reacted with 15 g of fluorine to form lithium fluoride:
2Li + F2  2LiF. After the reaction is complete, what will be present?
A) 2.16 mol lithium fluoride only
B) 0.789 mol lithium fluoride only
C) 2.16 mol lithium fluoride and 0.395 mol fluorine
D) 0.789 mol lithium fluoride and 1.37 mol lithium
E)
none of these
Consider the electrolysis of a brine solution:
2NaCl(aq) + H2O  Cl2(g) + H2(g) + 2NaOH(aq)
A 10.0-g sample of sodium chloride was placed in 10.0 g of water. If 3.85 g of Cl 2 was obtained, what was the percent yield of
Cl2?
A) 19.3%
B) 19.6%
C) 38.5%
D) 63.5%
E)
95.8%
Consider the following balanced equation:
A(g) + 5B(g)  3C + 4D
When equal masses of A and B are reacted, which is limiting?
A) If the molar mass of A is greater than the molar mass of B, then A must be limiting.
B) If the molar mass of A is less than the molar mass of B, then A must be limiting.
C) If the molar mass of A is greater than the molar mass of B, then B must be limiting.
D) If the molar mass of A is less than the molar mass of B, then B must be limiting.
E)
More information is needed.
88.
89.
90.
91.
92.
93.
Consider the following reaction:
4NH3(g) + 7O2(g)  4NO2(g) + 6H2O(l)
Consider an experiment in which you react ammonia and oxygen. At the end of the experiment, you find that you produced
27.0 g of water, and 8.52 g of ammonia is left over. Calculate the initial mass of ammonia. Assume the reaction went to
completion.
A) 10.8 g
B) 17.0 g
C) 25.5 g
D) 34.1 g
E)
68.0 g
Consider a reaction in which two reactants make one product (for example, consider the unbalanced A + B  C). You know
the following:
2.0 mol A (with an excess of B) can make a maximum of 2.0 mol C
3.0 mol B (with an excess of A) can make a maximum of 4.0 mol C
If you react 2.0 mol A and 3.0 mol B, what is the maximum amount of C that can be produced?
A) 2.0 mol
B) 4.0 mol
C) 5.0 mol
D) 6.0 mol
E)
More information is needed.
Hemoglobin is the protein that transports oxygen in mammals. Hemoglobin is 0.342% Fe by mass, and each hemoglobin
molecule contains four iron atoms. Calculate the molar mass of hemoglobin
The characteristic odor of pineapple is due to ethyl butyrate, a compound containing carbon, hydrogen, and oxygen. Combustion
of 2.78 g of ethyl butyrate leads to formation of 6.32 g of CO 2 and 2.58 g of H2O. The properties of the compound suggest that
the molar mass should be between 100 and 150. What is the molecular formula?
Consider the following two unbalanced equations.
CH4 + O2  CO2 + H2O
H2 + O2 H2O
Suppose you carry out each reaction with the same mass of oxygen (and with an excess of CH 4 and H2). In which case will you
make more water, and by what factor?
A 100.0-g mixture of methane (CH4) and propane (C3H8) reacts with oxygen to make carbon dioxide and water. The carbon
dioxide produced has a mass of 231.25 g. Determine the percent by mass of methane in the mixture.
Use the following to answer questions 94-96:
Acetylsalicylic acid, or aspirin (C9H8O4), is an analgesic (pain reliever). A typical aspirin tablet contains 500.0 mg of acetylsalicylic
acid.
94. Determine the molar mass of acetylsalicylic acid.
95. Determine the number of moles of acetylsalicylic acid per tablet.
96. Determine the number of molecules of acetylsalicylic acid in the tablet.
Answers
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
A
B
D
A
A
A
B
B
B
B
11.
12.
13.
14.
15.
16.
17.
18.
19.
20.
B
C
B
D
C
D
C
B
D
A
21.
22.
23.
24.
25.
26.
27.
28.
29.
30.
C
C
C
A
E
C
E
C
D
E
31.
32.
33.
34.
35.
36.
37.
38.
39.
40.
D
A
D
B
C
E
E
A
C
E
41.
42.
43.
44.
45.
46.
47.
48.
49.
50.
A
D
D
B
B
D
A
D
A
C
51.
52.
53.
54.
55.
56.
57.
58.
59.
60.
C
B
D
A
A
E
C
B
E
B
61.
62.
63.
64.
65.
66.
67.
68.
69.
70.
C
D
B
C
B
D
D
C
D
E
71.
72.
73.
74.
75.
76.
77.
78.
79.
80.
B
C
C
D
B
A
C
B
E
D
81.
82.
83.
84.
85.
86.
87.
88.
89.
C
D
D
B
D
D
D
C
A
90.
91.
92.
93.
94.
95.
96.
6.53X104 g/mol
C6H12Oy
You will make twice as much water with the second reaction
21.2% CH4
180.2 g/mol
2.775x10–3 mole/tablet
1.671x1021 molecules/tablet