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Chm 2.2 Energy: Conservation and Transfer - Chemical Reactions and Energy of Reactions Chapter 7, 8, 9 and 17
Multiple Choice
Identify the letter of the choice that best completes the statement or answers the question.
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1. In a chemical reaction
a. the mass of the reactants equals the mass of the products.
b. the mass of the products is greater than the mass of reactants.
c. the number of atoms in the reactants and products must change.
d. energy as heat must be added to the reactants.
2. Which observation does not indicate that a chemical reaction has occurred?
a. formation of a precipitate
c. evolution of heat and light
b. production of a gas
d. change in total mass of substances
3. When a solid produced by a chemical reaction separates from the solution it is called
a. a precipitate.
c. a molecule.
b. a reactant.
d. the mass of the product.
4. In writing a chemical equation that produces hydrogen gas, the correct representation of hydrogen gas is
a. H.
c. H2.
b. 2H.
d. OH.
5. What is the small whole number that appears in front of a formula in a chemical equation?
a. a subscript
c. a ratio
b. a superscript
d. a coefficient
6. To balance a chemical equation, it may be necessary to adjust the
a. coefficients.
c. formulas of the products.
b. subscripts.
d. number of products.
7. According to the law of conservation of mass, the total mass of the reacting substances is
a. always more than the total mass of the products.
b. always less than the total mass of the products.
c. sometimes more and sometimes less than the total mass of the products.
d. always equal to the total mass of the products.
8. A chemical equation is balanced when the
a. coefficients of the reactants equal the coefficients of the products.
b. same number of each kind of atom appears in the reactants and in the products.
c. products and reactants are the same chemicals.
d. subscripts of the reactants equal the subscripts of the products.
9. In the word equation, sodium oxide + water  sodium hydroxide, the formula for
sodium hydroxide is represented by
a. Na2OH.
c. NaO2.
b. NaOH.
d. Na2O.
10. Which word equation represents the reaction that produces water from hydrogen and oxygen?
a. Water is produced from hydrogen and oxygen.
b. Hydrogen plus oxygen yields water.
c. H2 + O2  water.
d. Water can be separated into hydrogen and oxygen.
11. How would oxygen be represented in the formula equation for the reaction of methane and oxygen to yield
carbon dioxide and water?
a. oxygen
c. O2
____ 12.
____ 13.
____ 14.
____ 15.
____ 16.
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____ 18.
____ 19.
____ 20.
____ 21.
____ 22.
____ 23.
____ 24.
b. O
d. O3
Which of the following is a formula equation for the formation of carbon dioxide from carbon and oxygen?
a. Carbon plus oxygen yields carbon dioxide. c. CO2  C + O2
b. C + O2  CO2
d. 2C + O  CO2
In an equation, the symbol for a substance in water solution is followed by
a. (1).
c. (aq).
b. (g).
d. (s).
When the equation Fe3O4 + Al  Al2O3 + Fe is correctly balanced, what is the coefficient of Fe?
a. 3
c. 6
b. 4
d. 9
Which coefficients correctly balance the formula equation
NH4NO2(s) N2(g) + H2O(l)?
a. 1, 2, 2
c. 2, 1, 1
b. 1, 1, 2
d. 2, 2, 2
Which coefficients correctly balance the formula equation CaO + H2O  Ca(OH)2?
a. 2, 1, 2
c. 1, 2, 1
b. 1, 2, 3
d. 1, 1, 1
After the first steps in writing an equation, the equation is balanced by
a. adjusting subscripts to the formula(s).
b. adjusting coefficients to the smallest whole-number ratio.
c. changing the products formed.
d. making the number of reactants equal to the number of products.
The complete balanced equation for the reaction between zinc hydroxide and acetic acid is
a. ZnOH + CH3COOH  ZnCH3COO + H2O.
b. Zn(OH)2 + CH3COOH  Zn + 2CO2 +3H2O.
c. Zn(OH)2 + 2CH3COOH  Zn(CH3COO)2 + 2H2O.
d. Zn(OH)2 + 2CH3COOH  Zn(CH3COO)2 + H2 + O2.
Which equation is not balanced?
a. 2H2 + O2  2H2O
b. 4H2 + 2O2  4H2O
c. H2 + H2 + O2  H2O + H2O
d. 2H2 + O2  H2O
In what kind of reaction do two or more substances combine to form a new compound?
a. decomposition reaction
c. double-displacement reaction
b. ionic reaction
d. synthesis reaction
The equation AX  A + X is the general equation for a
a. synthesis reaction.
c. combustion reaction.
b. decomposition reaction.
d. single-displacement reaction.
In what kind of reaction does one element replace a similar element in a compound?
a. displacement reaction
c. decomposition reaction
b. combustion
d. ionic reaction
The equation AX + BY  AY + BX is the general equation for a
a. synthesis reaction.
c. single-displacement reaction.
b. decomposition reaction.
d. double-displacement reaction.
The equation A + X  AX is the general equation for a(n)
a. combustion reaction.
c. synthesis reaction.
b. ionic reaction.
d. double-displacement reaction.
____ 25. In what kind of reaction does a single compound produce two or more simpler substances?
a. decomposition reaction
c. single-displacement reaction
b. synthesis reaction
d. ionic reaction
____ 26. The equation A + BX  AX + B is the general equation for a
a. double-displacement reaction.
c. single-displacement reaction.
b. decomposition reaction.
d. combustion reaction.
____ 27. In what kind of reaction do the ions of two compounds exchange places in aqueous solution to form two new
compounds?
a. synthesis reaction
c. decomposition reaction
b. double-displacement reaction
d. combustion reaction
____ 28. The reaction represented by the equation 2Mg(s) + O2(g)  2MgO(s) is a
a. synthesis reaction.
c. single-displacement reaction.
b. decomposition reaction.
d. double-displacement reaction.
____ 29. The reaction represented by the equation Mg(s) + 2HCl(aq)  H2(g) + MgCl2(aq) is a
a. composition reaction.
c. single-displacement reaction.
b. decomposition reaction.
d. double-displacement reaction.
____ 30. The reaction represented by the equation 2HgO(s)  2Hg(l) + O2(g) is a(n)
a. single-displacement reaction.
c. combustion reaction.
b. synthesis reaction.
d. decomposition reaction.
____ 31. The reaction represented by the equation Pb(NO3)2(aq) + 2KI(aq)  PbI2(s) + 2KNO3(aq) is a
a. double-displacement reaction.
c. decomposition reaction.
b. synthesis reaction.
d. combustion reaction.
____ 32. The reaction represented by the equation 2KClO3(s)  2KCl(s) + 3O2(g) is a(n)
a. synthesis reaction.
c. combustion reaction.
b. decomposition reaction.
d. ionic reaction.
____ 33. The reaction represented by the equation Cl2(g) + 2KBr(aq)  2KCl(aq) + Br2(l) is a(n)
a. synthesis reaction.
c. single-displacement reaction.
b. decomposition reaction.
d. combustion reaction.
____ 34. In one type of synthesis reaction, an element combines with oxygen to yield a(n)
a. acid.
c. oxide.
b. hydroxide.
d. metal.
____ 35. When heated, a metal carbonate decomposes into a metal oxide and
a. carbon.
c. oxygen.
b. carbon dioxide.
d. hydrogen.
____ 36. Oxides of active metals, such as CaO, react with water to produce
a. metal carbonates.
c. acids.
b. metal hydrides.
d. metal hydroxides.
____ 37. An active metal and a halogen react to form a(n)
a. salt.
c. acid.
b. hydroxide.
d. oxide.
____ 38. When a binary compound decomposes, what is produced?
a. an oxide
c. a tertiary compound
b. an acid
d. two elements
____ 39. Many metal hydroxides decompose when heated to yield metal oxides and
a. metal hydrides.
c. carbon dioxide.
b. water.
d. an acid.
____ 40. When a metal chlorate is heated, it decomposes to yield a metal chloride and
____ 41.
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____ 52.
____ 53.
____ 54.
a. a metal oxide.
c. hydrogen.
b. a metal hydroxide.
d. oxygen.
Some acids, such as carbonic acid, decompose to nonmetal oxides and
a. water.
c. oxygen.
b. a salt.
d. peroxide.
When heated, metallic chlorates decompose into
a. metallic oxides and chlorine.
b. metallic chlorides and oxygen.
c. a metal and a compound of chlorine and oxygen.
d. a metal, chlorine, and oxygen.
In the equation 2Al(s) + 3Fe(NO3)2(aq)  3Fe(s) + 2Al(NO3)3(aq), iron has been replaced by
a. nitrate.
c. aluminum.
b. water.
d. nitrogen.
Group 1 metals react with water to produce metal hydroxides and
a. metal hydroxides.
c. oxygen.
b. hydrochloric acid.
d. hydrogen.
The replacement of bromine by chlorine in a salt is an example of a single-displacement reaction by
a. halogens.
c. water.
b. sodium.
d. electrolysis.
When a slightly soluble solid compound is produced in a double-displacement reaction, a
a. gas bubbles off.
c. combustion reaction takes place.
b. precipitate is formed.
d. halogen is produced.
In a double-displacement reaction, hydrogen chloride and sodium hydroxide react to produce sodium
chloride. Another product is
a. sodium hydride.
c. water.
b. potassium chloride.
d. hydrogen gas.
Active metals react with certain acids, such as hydrochloric acid, to yield a metal compound and
a. oxygen.
c. chlorine.
b. hydrogen.
d. sodium.
Some metals, such as iron, react with steam to produce hydrogen gas and a
a. metal hydroxide.
c. metallic acid.
b. metal hydride.
d. metal oxide.
When potassium reacts with water, one product formed is
a. hydrogen gas.
c. potassium oxide.
b. oxygen gas.
d. salt.
The reaction of calcium oxide, CaO, with water yields
a. calcium and oxygen gas.
c. calcium and a salt.
b. calcium hydroxide.
d. carbon dioxide and water.
Predict the product of the reaction represented by the following equation:
MgO + CO2 
a. MgCO3
c. MgC + O3
b. Mg + CO3
d. MgCO2 + O
Magnesium hydroxide decomposes to yield magnesium oxide and
a. hydrogen.
c. water.
b. oxygen.
d. salt.
When sodium chlorate, NaClO3, decomposes, the products are
a. sodium hydroxide and water.
c. sodium and chlorine oxide.
b. sodium oxide and chlorine.
d. sodium chloride and oxygen.
____ 55. If chlorine gas is produced by halogen replacement, the other halogen in the reaction must be
a. bromine.
c. astatine.
b. iodine.
d. fluorine.
____ 56. The formulas for the products of the reaction between sodium hydroxide and sulfuric acid are
a. Na2SO4 and H2O.
c. SI4 and Na2O.
b. NaSO4 and H2O.
d. S + O2 and Na.
____ 57. What is the balanced equation when aluminum reacts with copper(II) sulfate?
a. Al + Cu2S  Al2S + Cu
b. 2Al + 3CuSO4  Al2(SO4)3 + 3Cu
c. Al + CuSO4  AlSO4 + Cu
d. 2Al + Cu2SO4  Al2SO4 + 2Cu
____ 58. The ability of an element to react is the element's
a. valence.
c. stability.
b. activity.
d. electronegativity.
____ 59. What is the name of a list of elements arranged according to the ease with which they undergo certain
chemical reactions?
a. reactivity list
c. activity series
b. reaction sequence
d. periodic list
____ 60. An element in the activity series can replace any element
a. in the periodic table.
c. above it on the list.
b. below it on the list.
d. in its group.
____ 61. What can be predicted by using an activity series?
a. whether a certain chemical reaction will occur
b. the amount of energy released by a chemical reaction
c. the electronegativity values of elements
d. the melting points of elements
____ 62. Predict what happens when calcium metal is added to a solution of magnesium chloride.
a. No reaction occurs.
c. Magnesium calcite forms.
b. Calcium chloride forms.
d. Gaseous calcium is produced.
____ 63. Predict what happens when zinc is added to water.
a. No reaction occurs.
c. Zinc oxide forms.
b. Steam is produced.
d. Hydrogen is released.
____ 64. Predict what happens when lead is added to nitric acid.
a. No reaction occurs.
c. Lead oxide forms.
b. Oxygen is released.
d. Hydrogen is released.
____ 65. Predict what happens when nickel is added to a solution of potassium chloride.
a. No reaction occurs.
c. Potassium nickel chloride forms.
b. Nickel chloride forms.
d. Hydrochloric acid forms.
____ 66. Magnesium bromide (aq) + chlorine (g) yields
a. Mg(s) and BrCl(aq).
c. MgBrCl(aq).
b. MgCl(aq) and Br2(l).
d. MgCl2(aq) and Br2(l).
____ 67. Which reaction does not occur?
a. 2HF(aq) + Cl2(g)  F2(g) + 2HCl(aq)
b. 2Na(s) + ZnF2(aq)  2NaF(aq) + Zn(s)
c. Fe(s) + CuCl2(aq)  FeCl2(aq) + Cu(s)
d. 2HCl(aq) + Mg(s)  MgCl2(aq) + H2(g)
____ 68. Which reaction can be predicted from the activity series?
a. 2Cl(g)  Cl2(g)
____ 69.
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____ 78.
____ 79.
b. HCl(aq) + NaOH(aq)  NaCl(aq) + H2O(l)
c. 2H2O(aq) + 2Na(s)  2NaOH(aq) + H2(g)
d. Cl2(g)  2Cl(g)
The coefficients in a chemical equation represent the
a. masses, in grams, of all reactants and products.
b. relative numbers of moles of reactants and products.
c. number of atoms in each compound in a reaction.
d. number of valence electrons involved in the reaction.
In the reaction represented by the equation N2 + 3H2  2NH3, what is the mole ratio of nitrogen to ammonia?
a. 1:1
c. 1:3
b. 1:2
d. 2:3
In the reaction represented by the equation 2Al2O3  4Al + 3O2, what is the mole ratio of aluminum to
oxygen?
a. 10:6
c. 2:3
b. 3:4
d. 4:3
In the reaction represented by the equation C + 2H2  CH4, what is the mole ratio of hydrogen to methane?
a. 1:1
c. 1:2
b. 2:1
d. 2:4
In the reaction represented by the equation N2 + 3H2  2NH3, what is the mole ratio of hydrogen to
ammonia?
a. 1:1
c. 3:2
b. 2:1
d. 6:8
The Haber process for producing ammonia commercially is represented by the equation N2(g) + 3H2(g) 
2NH3(g). To completely convert 9.0 mol hydrogen gas to ammonia gas, how many moles of nitrogen gas are
required?
a. 1.0 mol
c. 3.0 mol
b. 2.0 mol
d. 6.0 mol
In the equation 2KClO3  2KCl + 3O2, how many moles of oxygen are produced when 3.0 mol of KClO3
decompose completely?
a. 1.0 mol
c. 3.0 mol
b. 2.5 mol
d. 4.5 mol
For the reaction represented by the equation C + 2H2  CH4, how many moles of hydrogen are required to
produce 10 mol of methane, CH4?
a. 2 mol
c. 10 mol
b. 4 mol
d. 20 mol
For the reaction represented by the equation 2H2 + O2 2H2O, how many moles of water can be produced
from 6.0 mol of oxygen?
a. 2.0 mol
c. 12 mol
b. 6.0 mol
d. 18 mol
For the reaction represented by the equation N2 + 3H2  2NH3, how many moles of nitrogen are required to
produce 18 mol of ammonia?
a. 9.0 mol
c. 27 mol
b. 18 mol
d. 36 mol
For the reaction represented by the equation AgNO3 + NaCl  NaNO3 + AgCl, how many moles of silver
chloride, AgCl, are produced from 7.0 mol of silver nitrate AgNO3?
a. 1.0 mol
c. 7.0 mol
b. 2.3 mol
d. 21 mol
Use the table below to answer the following questions.
Element
Bromine
Calcium
Carbon
Chlorine
Cobalt
Copper
Fluorine
Hydrogen
Iodine
Iron
Lead
Magnesium
Mercury
Nitrogen
Oxygen
Potassium
Sodium
Sulfur
Symbol
Br
Ca
C
Cl
Co
Cu
F
H
I
Fe
Pb
Mg
Hg
N
O
K
Na
S
Atomic Mass
79.90
40.08
12.01
35.45
58.93
63.55
19.00
1.01
126.90
55.85
207.2
24.30
200.59
14.01
15.00
39.10
22.99
32.01
____ 80. For the reaction represented by the equation 2Na + 2H2O  2NaOH + H2, how many grams of sodium
hydroxide are produced from 3.0 mol of sodium with an excess of water?
a. 40. g
c. 120 g
b. 80. g
d. 240 g
____ 81. For the reaction represented by the equation SO3 + H2O  H2SO4, how many grams of sulfur trioxide are
required to produce 4.00 mol of sulfuric acid in an excess of water?
a. 80.0 g
c. 240. g
b. 160. g
d. 320. g
____ 82. For the reaction represented by the equation 2Fe + O2  2FeO, how many grams of iron(II) oxide are
produced from 8.00 mol of iron in an excess of oxygen?
a. 71.8 g
c. 712 g
b. 575 g
d. 1310 g
____ 83. For the reaction represented by the equation 2Na + Cl2  2NaCl, how many grams of chlorine gas are
required to react completely with 2.00 mol of sodium?
a. 35.5 g
c. 141.8 g
b. 70.9 g
d. 212.7 g
____ 84. For the reaction represented by the equation 2HNO3 + Mg(OH)2  Mg(NO3)2 + 2H2O, how many grams of
magnesium nitrate are produced from 8.00 mol of nitric acid, HNO3, and an excess of Mg(OH)2?
a. 148 g
c. 593 g
b. 445 g
d. 818 g
____ 85. For the reaction represented by the equation CH4 + 2O2  CO2 + 2H2O, how many moles of carbon dioxide
are produced from the combustion of 100. g of methane?
a. 6.23 mol
c. 12.5 mol
b. 10.8 mol
d. 25 mol
____ 86. For the reaction represented by the equation Pb(NO3)2 + 2KI  PbI2 + 2KNO3, how many moles of lead(II)
iodide are produced from 300. g of potassium iodide and an excess of Pb(NO3)2?
____ 87.
____ 88.
____ 89.
____ 90.
____ 91.
____ 92.
____ 93.
____ 94.
____ 95.
____ 96.
____ 97.
____ 98.
a. 0.904 mol
c. 3.61 mol
b. 1.81 mol
d. 11.0 mol
For the reaction represented by the equation Cl2 + 2KBr  2KCl + Br2, how many moles of potassium
chloride are produced from 119 g of potassium bromide?
a. 0.119 mol
c. 0.581 mol
b. 0.236 mol
d. 1.00 mol
For the reaction represented by the equation 3Fe + 4H2O  Fe3O4 + 4H2, how many moles of iron(III) oxide
are produced from 500. g of iron in an excess of H2O?
a. 1.04 mol
c. 8.95 mol
b. 2.98 mol
d. 12.98 mol
For the reaction represented by the equation 2KlO3  2KCl + 3O2, how many moles of potassium chlorate
are required to produce 250. g of oxygen?
a. 2.00 mol
c. 4.97 mol
b. 4.32 mol
d. 5.21 mol
Ozone, O3, is produced by the reaction represented by the following equation:
What mass of ozone will form from the reaction of 2.0 g of NO2 in a car's exhaust and excess oxygen?
a. 1.1 g O3
c. 2.1 g O3
b. 1.8 g O3
d. 4.2 g O3
For the reaction represented by the equation Cl2 + 2KBr  2KCl + Br2, how many grams of potassium
chloride can be produced from 300. g each of chlorine and potassium bromide?
a. 98.7 g
c. 188 g
b. 111 g
d. 451 g
For the reaction represented by the equation 2Na + 2H2O  2NaOH + H2, how many grams of hydrogen are
produced if 120. g of sodium and 80. g of water are available?
a. 4.5 g
c. 80. g
b. 45 g
d. 200 g
For the reaction represented by the equation 2Na + Cl2  2NaCl, how many grams of sodium chloride can be
produced from 500. g each of sodium and chlorine?
a. 112 g
c. 409 g
b. 319 g
d. 824 g
For the reaction represented by the equation SO3 + H2O  H2SO4, how many grams of sulfuric acid can be
produced from 200. g of sulfur trioxide and 100. g of water?
a. 100. g
c. 245 g
b. 200. g
d. 285 g
Which reactant controls the amount of product formed in a chemical reaction?
a. excess reactant
c. composition reactant
b. mole ratio
d. limiting reactant
For the reaction represented by the equation SO3 + H2O  H2SO4, calculate the percentage yield if 500. g of
sulfur trioxide react with excess water to produce 575 g of sulfuric acid.
a. 82.7%
c. 91.2%
b. 88.3%
d. 93.9%
For the reaction represented by the equation Cl2 + 2KBr  2KCl + Br2, calculate the percentage yield if 200.
g of chlorine react with excess potassium bromide to produce 410. g of bromine.
a. 73.4%
c. 91.0%
b. 82.1%
d. 98.9%
For the reaction represented by the equation CH4 + 2O2  2H2O + CO2, calculate the percentage yield of
carbon dioxide if 1000. g of methane react with excess oxygen to produce 2300. g of carbon dioxide.
a. 83.88%
c. 92.76%
b. 89.14%
d. 96.78%
____ 99. For the reaction represented by the equation Mg + 2HCl  H2 + MgCl2, calculate the percentage yield of
magnesium chloride if 100. g of magnesium react with excess hydrochloric acid to yield 330. g of magnesium
chloride.
a. 71.8%
c. 81.6%
b. 74.3%
d. 84.2%
____ 100.
____ 101.
____ 102.
____ 103.
____ 104.
____ 105.
____ 106.
____ 107.
____ 108.
____ 109.
What is E for the reaction in the diagram above?
a. + 200 kJ
c. +50 kJ
b. -200 kJ
d. - 50 kJ
The reaction illustrated in the diagram above is
a. endothermic
c. both endothermic and exothermic
b. exothermic
d. neither endothermic or exothermic
Calcualte Ea for the reaction given by the diagram in question #100.
a. +200 kJ
c. +250
b. -200 kJ
d. - 250 kJ
What is the percentage composition of CF4?
a. 20% C, 80% F
c. 16.8% C, 83.2% F
b. 13.6% C, 86.4% F
d. 81% C, 19% F
What is the percentage composition of CO?
a. 50% C, 50% O
c. 25% C, 75% O
b. 12% C, 88% O
d. 43% C, 57% O
What is the percentage composition of CuCl2?
a. 33% Cu, 66% Cl
c. 65.50% Cu, 34.50% Cl
b. 50% Cu, 50% Cl
d. 47.27% Cu, 52.73% Cl
The percentage composition of sulfur in SO2 is about 50%. What is the percentage of oxygen in this
compound?
a. 25%
c. 75%
b. 50%
d. 90%
What is the mass percentage of chlorine in NaCl?
a. 35.45%
c. 60.7%
b. 50%
d. 64.5%
What is the empirical formula for a compound that is 31.9% potassium, 28.9% chlorine, and 39.2% oxygen?
a. KClO2
c. K2Cl2O3
b. KClO3
d. K2Cl2O5
What is the empirical formula for a compound that is 43.6% phosphorus and 56.4% oxygen?
a. P3O7
c. P2O3
____ 110.
____ 111.
____ 112.
____ 113.
____ 114.
____ 115.
____ 116.
____ 117.
____ 118.
____ 119.
____ 120.
____ 121.
____ 122.
b. PO3
d. P2O5
What is the empirical formula for a compound that is 53.3% O and 46.7% Si?
a. SiO
c. Si2O
b. SiO2
d. Si2O3
A compound contains 259.2 g of F and 40.8 g of C. What is the empirical formula for this compound?
a. CF4
c. CF
b. C4F
d. CF2
A compound contains 64 g of O and 8 g of H. What is the empirical formula for this compound?
a. H2O
c. HO2
b. H2O2
d. HO
What is the empirical formula for a compound that is 36.1% Ca and 63.9% Cl?
a. CaCl
c. CaCl2
b. Ca2Cl
d. Ca2Cl2
A compound contains 27.3 g of C and 72.7 g of O. What is the empirical formula for this compound?
a. CO
c. C2O
b. CO2
d. C2O4
The molecular formula for vitamin C is C6H8O6. What is the empirical formula?
a. CHO
c. C3H4O3
b. CH2O
d. C2H4O2
Of the following molecular formulas for hydrocarbons, which is an empirical formula?
a. CH4
c. C3H6
b. C2H2
d. C4H10
A compound's empirical formula is C2H5. If the formula mass is 58 amu, what is the molecular formula?
a. C3H6
c. C5H8
b. C4H10
d. C5H15
A compound's empirical formula is N2O5. If the formula mass is 108 amu, what is the molecular formula?
a. N2O5
c. NO3
b. N4O10
d. N2O4
A compound's empirical formula is CH. If the formula mass is 26 amu, what is the molecular formula?
a. C2H2
c. CH4
b. CH3
d. C4H
A compound's empirical formula is NO2. If the formula mass is 92 amu, what is the molecular formula?
a. NO
c. NO4
b. N2O2
d. N2O4
A compound's empirical formula is CH3. If the formula mass is 30 amu, what is the molecular formula?
a. CH3
c. C2H6
b. CH4
d. C3H9
A compound's empirical formula is HO. If the formula mass is 34 amu, what is the molecular formula?
a. H2O
c. HO3
b. H2O2
d. H2O3
Short Answer
123. When balancing a chemical equation, why must the formula subscripts remain unchanged?
124. Consider the reaction represented by the equation 2Al(s) + 3ZnCl2(aq) ?. Briefly explain how the activity
series is used to predict the outcome and products of the reaction.
Essay
125. The two chemical equations below appear to describe the same chemical reaction. Explain how the two
reactions are different from each other. Hypothesize any differences you might be able to observe in these two
reactions represented by the following equations.
Mg(s) + 2H2O(l)  Mg(OH)2(aq) + H2(g)
Mg(l) + 2H2O(g)  Mg(OH)2(aq) + H2(g)
126. Consider the equation O2(g) + CS2(l)  CO2(g) + SO2(g). How does the equation violate the law of
conservation of mass? How can the equation be rewritten to conform to the law of conservation of mass?
Problem
127. Write a balanced chemical equation for the following reaction: iron plus copper(I) nitrate yields iron(II)
nitrate plus copper.
128. Write a balanced chemical equation for the synthesis of liquid phosphorus trichloride, PCl3, from white
phosphorus, P4, and chlorine gas.
129. Tell what type of chemical reaction is represented by the following formula equation. Then balance the
equation.
C3H8(g) + O2(g)
CO2(g) + H2O(l)
130. Tell what type of chemical reaction is represented by the following formula equation. Then balance the
equation.
Ga(s) + S(s)
Ga2S3(s)
131. Tell what type of chemical reaction is represented by the following formula equation. Then balance the
equation.
KBr(aq) + Mg(OH)2(aq)
KOH(aq) + MgBr2(aq)
132. Use the activity series to determine if the following reaction is possible. If it is possible, write the products
and balance the equation. If not, explain.
4Cr(s) + 3O2(g)
133. Use the activity series to determine if the following reaction is possible. If it is possible, write the products
and balance the equation. If not, explain.
2Sb + 6HCl
134. Use the activity series to determine if the following reaction is possible. If it is possible, write the products
and balance the equation. If not, explain.
2K(s) + ZnCl2(aq)
Chm 2.2 Energy: Conservation and Transfer - Chemical Reactions and Energy of Reactions Chapter 7, 8, 9 and 17
Answer Section
MULTIPLE CHOICE
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
14.
15.
16.
17.
18.
19.
20.
21.
22.
23.
24.
25.
26.
27.
28.
29.
30.
31.
32.
33.
34.
35.
36.
37.
38.
39.
40.
ANS:
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ANS:
ANS:
ANS:
ANS:
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ANS:
ANS:
ANS:
ANS:
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ANS:
ANS:
ANS:
ANS:
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ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
A
D
A
C
D
A
D
B
B
B
C
B
C
D
B
D
B
C
D
D
B
A
D
C
A
C
B
A
C
D
A
B
C
C
B
D
A
D
B
D
DIF:
DIF:
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DIF:
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DIF:
DIF:
DIF:
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DIF:
DIF:
DIF:
DIF:
DIF:
DIF:
DIF:
DIF:
I
I
I
I
I
I
I
I
I
II
II
II
I
III
III
III
II
III
III
I
II
I
II
II
I
II
I
II
II
II
II
II
II
II
II
II
II
II
II
II
REF:
REF:
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REF:
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
OBJ:
OBJ:
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1
1
1
2
2
2
2
2
3
3
3
3
3
4
4
4
4
4
4
1
1
1
1
1
1
1
1
2
2
2
2
2
2
3
3
3
3
3
3
3
41.
42.
43.
44.
45.
46.
47.
48.
49.
50.
51.
52.
53.
54.
55.
56.
57.
58.
59.
60.
61.
62.
63.
64.
65.
66.
67.
68.
69.
70.
71.
72.
73.
74.
75.
76.
77.
78.
79.
80.
ANS: A
ANS: B
ANS: C
ANS: D
ANS: A
ANS: B
ANS: C
ANS: B
ANS: D
ANS: A
ANS: B
ANS: A
ANS: C
ANS: D
ANS: D
ANS: A
ANS: B
ANS: B
ANS: C
ANS: B
ANS: A
ANS: B
ANS: A
ANS: D
ANS: A
ANS: D
ANS: A
ANS: C
ANS: B
ANS: B
ANS: D
ANS: B
ANS: C
ANS: C
ANS: D
ANS: D
ANS: C
ANS: A
ANS: C
ANS: C
Solution:
DIF: III
81. ANS: D
DIF:
DIF:
DIF:
DIF:
DIF:
DIF:
DIF:
DIF:
DIF:
DIF:
DIF:
DIF:
DIF:
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DIF:
DIF:
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DIF:
DIF:
DIF:
DIF:
DIF:
DIF:
DIF:
DIF:
DIF:
DIF:
DIF:
DIF:
DIF:
DIF:
DIF:
DIF:
II
II
II
I
II
I
II
I
I
I
III
III
III
III
III
III
III
I
I
I
II
III
III
III
III
III
III
III
I
III
III
III
III
III
III
III
III
III
III
REF: 2
REF:
REF:
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2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
3
1
1
1
1
1
1
1
1
1
1
2
OBJ: 2
OBJ:
OBJ:
OBJ:
OBJ:
OBJ:
OBJ:
OBJ:
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OBJ:
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3
3
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
1
1
1
1
2
2
2
2
2
2
2
1
3
3
3
3
3
3
3
3
3
1
Solution:
DIF: III
82. ANS: B
Solution:
REF: 2
OBJ: 2
DIF: III
83. ANS: B
Solution:
REF: 2
OBJ: 2
DIF: III
84. ANS: C
Solution:
REF: 2
OBJ: 2
DIF: III
85. ANS: A
Solution:
REF: 2
OBJ: 2
DIF: III
86. ANS: A
Solution:
REF: 2
OBJ: 3
DIF: III
87. ANS: D
Solution:
REF: 2
OBJ: 3
DIF: III
88. ANS: B
Solution:
REF: 2
OBJ: 3
DIF: III
89. ANS: D
Solution:
REF: 2
OBJ: 3
DIF: III
90. ANS: C
Solution:
REF: 2
OBJ: 3
DIF: III
91. ANS: C
Solution:
REF: 2
OBJ: 4
Since Cl2 would produce the most KCl, KBr is the limiting reactant, thus 188 G KCl is produced.
DIF: III
92. ANS: A
Solution:
REF: 2
OBJ: 4
Since Na would produce the most H2, H2O is the limiting reactant, thus 4.5 g H2 is produced.
DIF: III
93. ANS: D
Solution:
REF: 2
OBJ: 4
Since Na would produce the most NaCl, Cl2 is the limiting reactant, thus 824 g NaCl is produced.
DIF: III
94. ANS: C
Solution:
REF: 2
OBJ: 4
Since H2O would produce the most H2SO4, SO3 is the limiting reactant, thus 245 g H2SO4 is produced.
DIF: III
95. ANS: D
96. ANS: D
Solution:
REF: 2
DIF: I
OBJ: 4
REF: 3
DIF: III
97. ANS: C
Solution:
REF: 3
OBJ: 4
DIF: III
98. ANS: A
Solution:
REF: 3
OBJ: 4
OBJ: 1
DIF: III
99. ANS: D
Solution:
REF: 3
OBJ: 4
DIF: III
ANS: C
ANS: A
ANS: A
ANS: B
Solution:
REF: 3
OBJ: 4
DIF: III
104. ANS: D
Solution:
REF: 3
OBJ: 4
DIF: III
105. ANS: D
Solution:
REF: 3
OBJ: 4
DIF: III
106. ANS: B
107. ANS: C
Solution:
REF: 3
DIF: II
OBJ: 4
REF: 3
100.
101.
102.
103.
OBJ: 4
DIF: III
108. ANS: B
Solution:
REF: 3
OBJ: 4
DIF: III
109. ANS: D
Solution:
REF: 4
OBJ: 2
DIF: III
110. ANS: B
Solution:
REF: 4
OBJ: 2
DIF: III
111. ANS: A
REF: 4
OBJ: 2
Solution:
DIF: III
112. ANS: A
Solution:
REF: 4
OBJ: 2
DIF: III
113. ANS: C
Solution:
REF: 4
OBJ: 2
DIF: III
114. ANS: B
Solution:
REF: 4
OBJ: 2
DIF: III
REF: 4
OBJ: 2
115. ANS: C
116. ANS: A
117. ANS: B
Solution:
DIF: III
DIF: III
REF: 4
REF: 4
DIF: III
118. ANS: A
Solution:
REF: 4
OBJ: 4
DIF: III
119. ANS: A
Solution:
REF: 4
OBJ: 4
DIF: III
120. ANS: D
Solution:
REF: 4
OBJ: 4
DIF: III
121. ANS: C
Solution:
REF: 4
OBJ: 4
DIF: III
122. ANS: B
Solution:
REF: 4
OBJ: 4
OBJ: 3
OBJ: 3
DIF: III
REF: 4
OBJ: 4
SHORT ANSWER
123. ANS:
Changing the subscript in a formula changes the chemical composition of the compound.
DIF: I
REF: 2
OBJ: 2
124. ANS:
In the activity series, aluminum is more active than zinc. Aluminum will replace zinc forming aluminum
chloride and leaving zinc metal.
DIF: II
REF: 3
OBJ: 2
ESSAY
125. ANS:
The conditions under which the two reactions take place are different. In one case, solid magnesium is added
to liquid water, while in the other case, liquid magnesium reacts with gaseous water (perhaps steam).
Although the products are the same in each case, one might expect the second reaction to proceed more
rapidly than the first because of the higher temperature of the water (steam) and the breaking of the crystal
lattice in magnesium.
DIF: II
REF: 1
OBJ: 3
126. ANS:
In the equation shown, there are more oxygen atoms in the products than in the reactants and more sulfur
atoms in the reactants than in the products. Both conditions violate the law of conservation of mass. The
equation is balanced as follows: 3O2 + CS2  CO2 +2SO2.
DIF: II
REF: 2
OBJ: 2
PROBLEM
127. ANS:
Fe(s) + 2CuNO3(aq)  Fe(NO3)2(aq) + 2Cu(s)
DIF: II
REF: 2
128. ANS:
P4(s) + 6Cl2(g)  4PCl3(l)
OBJ: 2
DIF: II
129. ANS:
OBJ: 2
REF: 2
combustion, C3H8(g) + 5O2(g)
DIF: III
130. ANS:
REF: 3
3CO2(g) + 4H2O(l)
OBJ: 1
synthesis, 2Ga(s) + 3S(s)
Ga2S3(s)
DIF: II
REF: 3
OBJ: 2
131. ANS:
double-displacement, 2KBr(aq) + Mg(OH)2(aq)
2KOH(aq) + MgBr2(aq)
DIF: III
REF: 2
132. ANS:
reaction will occur, 4Cr(s) + 3O2(g)
OBJ: 2
2Cr2O3(s)
DIF: III
REF: 3
OBJ: 2
133. ANS:
no reaction; Antimony is not highly active and will not replace hydrogen in an acid.
DIF: III
REF: 3
134. ANS:
reaction will occur, 2K(s) + ZnCl2(aq)
DIF: III
REF: 3
OBJ: 2
2KCl(aq) + Zn(s)
OBJ: 2