Chapter 8 Chemical Reactions Chapter Review Answers
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The evolution of energy, the production of a gas, the formation of a precipitate, and a color change.
A correctly written chemical equation must represent the known facts, contain the correct formulas for the
reactants and products, and satisfy the law of conservation of mass.
a. It is a number that appears in front of a formula in a chemical equation.
b. The number of atoms of each type in the formula is multiplied by the coefficient.
methane + oxygen  carbon dioxide + water;
CH4(g) + O2(g)  CO2(g) + H2O(g);
CH4(g) + 2O2(g)  CO2(g) + 2H2O(g)
A chemical equation provides the number of molecules, moles, and atoms of each element or compound composing
the reactants and products as well as the mole ratios of the reactants to each other and to the products.
Word and formula equations have only qualitative meaning; they do not express the relative quantities of a
reaction’s reactants or products.
a. a solution in water
b. a substance that accelerates a chemical reaction but can be recovered unchanged
c. a chemical reaction in which the products re-form the original reactants
a. KOH
d. CCl4
b. Ca(NO3)2
e. MgBr2
c. Na2CO3
(1) Balance different types of atoms one at a time; (2) balance types of atoms that appear only once on each side of
the equation first; (3) balance as single units any polyatomic ions that appear on both sides of the equation; and
(4) balance H atoms and O atoms last.
a. 6N
b. 4H, 2O
c. 4H, 4N, 12O
d. 2Ca, 4O, 4H
e. 3Ba, 6Cl, 18O
f. 5Fe, 10N, 30O
g. 12Mg, 8P, 32O
h. 4N, 16H, 2S, 8O
i. 12Al, 18Se, 72O
j. 12C, 32H
a. 2ZnS(s) + 3O2(g)  2ZnO(s) + 2SO2(g)
b. 2HCl(aq) + Ba(OH)2(aq)  BaCl2(aq) + 2H2O(l )
c. 2HNO3(aq) + Ca(OH)2(aq)  Ca(NO3)2(aq) + 2H2O(l )
a. Solid zinc sulfide reacts with oxygen gas to form solid zinc oxide and sulfur dioxide gas.
b. When solid calcium hydride is added to water, aqueous calcium hydroxide and hydrogen gas are formed.
c. Aqueous silver nitrate mixed with aqueous potassium iodide produces a precipitate of silver iodide and aqueous
potassium nitrate.
a. H2 + Cl2 2HCl
b. 2Al + Fe2O3  Al2O3 + 2Fe
c. Pb(CH3COO)2 + H2S  PbS + 2CH3COOH
a. LiO2 is an incorrect formula; 4Li + O2  2Li2O
b. H2Cl2 is an incorrect formula; H2 + Cl2  2HCl
c. MgO2 is an incorrect formula, and the equation as written is not balanced; MgCO3  MgO + CO2
d. I is an incorrect formula for iodine, and the equation is not balanced; 2NaI + Cl2  2NaCl + I2
a. 4Al + 3O2  2Al2O3
b. P4O10 + 6H2O  4H3PO4
c. Fe2O3 + 3CO  2Fe + 3CO2
CH4(g) + 4Cl2(g)  CCl4(l ) + 4HCl(g)
a. 2Mg + O2  2MgO
b. 4Fe + 3O2  2Fe2O3
c. 2Li + Cl2  2LiCl
d. Ca + I2  CaI2
(1) In a synthesis reaction, two or more substances combine to form a new substance: A + X  AX
(2) In a decomposition reaction, a single compound undergoes a reaction that produces two or more simpler
substances: AX  A + X
(3) In a single-displacement reaction, one element replaces another element in a compound:
A + BX  AX + B or Y + BX  BY + X
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(4) In a double-displacement reaction, the ions of two compounds exchange places in an aqueous solution to form
two new compounds: AX + BY  BX + AY
(5) In a combustion reaction, a substance combines with oxygen, releasing a large amount of energy in the form of
light and heat; for example, C3H8(g) + 5O2(g)  3CO2(g) + 4H2O(g)
by the addition of energy in the form of electricity or heat
electrolysis
a. aqueous solutions
b. They generally involve less energy than synthesis or decomposition reactions do.
a. Sodium and oxygen react to form sodium oxide; 4Na + O2  2Na2O
b. Magnesium and fluorine combine to form magnesium fluoride; Mg + F2  MgF2
∆
a. 2HgO → 2Hg + O2
𝑒𝑙𝑒𝑐𝑡𝑟𝑖𝑐𝑖𝑡𝑦
b. 2H2O(l ) →
2H2(g) + O2(g)
∆
c. 2Ag2O → 4Ag + O2
𝑒𝑙𝑒𝑐𝑡𝑟𝑖𝑐𝑖𝑡𝑦
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d. CuCl2 →
Cu + Cl2
a. Zn + Pb(NO3)2  Pb + Zn(NO3)2
b. 2Al + 3Hg(CH3COO)2  3Hg + 2Al(CH3COO)3
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c. 2Al + 3NiSO4  3Ni + Al2(SO4)3
d. 2Na + 2H2O  2NaOH + H2
a. AgNO3(aq) + NaCl(aq)  NaNO3(aq) + AgCl(s)
b. Mg(NO3)2(aq) + 2KOH(aq)  Mg(OH)2(s) + 2KNO3(aq)
c. 3LiOH(aq) + Fe(NO3)3(aq)  Fe(OH)3(s) + 3LiNO3(aq)
a. CH4 + 2O2  CO2 + 2H2O
b. 2C3H6 + 9O2  6CO2 + 6H2O
c. C5H12 + 8O2  5CO2 + 6H2O
a. H2 + I2  2HI; synthesis
b. 2Li + 2HCl  2LiCl + H2; single displacement
c. Na2CO3  Na2O + CO2; decomposition
d. 2HgO  2Hg + O2; decomposition
e. Mg(OH)2  MgO + H2O; decomposition
a. magnesium hydroxide; Mg(OH)2  MgO + H2O
b. lead(II) hydroxide; Pb(OH)2  PbO + H2O
c. lithium chlorate; 2LiClO3  2LiCl + 3O2
d. barium chlorate; Ba(ClO3)2  BaCl2 + 3O2 Ni(ClO3)2  NiCl2 + 3O2
a. oxygen, carbon dioxide; C3H8 + 5O2  3CO2 + 4H2O
b. pentane; C5H12 + 8O2  5CO2 + 6H2O
c. oxygen, carbon dioxide, water; C2H5OH + 3O2  2CO2 + 3H2O
a. Zn + S  ZnS; synthesis
b. AgNO3 + KI  AgI + KNO3; double displacement
c. C7H8 + 9O2  7CO2 + 4H2O; combustion
d. C9H20 + 14O2  9CO2 + 10H2O; combustion
a. the element’s ability to react
b. For metals, the activity describes the element’s ability to lose electrons. For nonmetals, it describes the ability
to gain electrons.
a. a set of elements listed according to the ease with which the elements undergo certain chemical reactions
b. Elements are usually listed in order of their tendency to undergo single-displacement reactions.
An element in such a series can replace any element listed below it.
a. The activity series of metals is based on the ease with which metal atoms lose electrons to form ions in aqueous
solution; the higher a metal is in the series, the more easily its atoms lose electrons and the greater its reactivity.
b. The greater the distance is, the greater the likelihood that one metal will replace the other in a
reaction.
a. K
b. Al
c. Cr
d. F
e. Ag f. Cl
g. Sr
h. F
a. Ni(s) + CuCl2(aq)  NiCl2(aq) + Cu(s)
b. Zn(s) + Pb(NO3)2(aq)  Zn(NO3)2(aq) + Pb(s)
c. Cl2(g) + 2KI(aq)  2KCl(aq) + I2(s)
d. No Reaction
e. Ba(s) + 2H2O(l)  H2(g) + Ba(OH)2(s)
a. 2Ca(s) + O2(g)  2CaO(s)
b. 2Ni(s) + O2(g)  2NiO(s)
c. No Reaction
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a. 4.0 mol NH3, 2.0 mol N2, & 6.0 mol H2O
b. 6.0 mol O2, 4.0 mol N2, & 12.0 mol H2O
c. 2.0 mol NH3, 1.5 mol O2, & 3.0 mol H2O
d. 0.27 mol NH3, 0.20 mol O2, & 0.13 mol N2
a. Potassium and chlorine react to form potassium chloride; 2K + Cl2  2KCl
b. Hydrogen and iodine react to produce hydroiodic acid; H2 + I2  2HI
c. Magnesium and oxygen react to produce magnesium oxide; 2Mg + O2  2MgO
Pt
𝑒𝑙𝑒𝑐𝑡𝑟𝑖𝑐𝑖𝑡𝑦
2NaCl(aq) + 2H2O →
2NaOH(aq) + H2(g) + Cl2(g)
a. Ca(OH)2 + (NH4)2SO4  CaSO4 + 2NH3 + 2H2O
b. 2C2H6 + 7O2  4CO2 + 6H2O
c. 2Cu2S + 3O2  2Cu2O + 2SO2
d. 2Al + 3H2SO4  Al2(SO4)3 + 3H2
a. 4Al(s) + 3O2(g)  2Al2O3(s)
b. No Reaction
a. (NH4)2S(aq) + ZnCl2(aq)  2NH4Cl(aq) + ZnS(s); Double-Displacement Reaction
b. 2Al(s) + 3Pb(NO3)2(aq)  3Pb(s) + 2Al(NO3)3(aq); Single-Displacement Reaction
c. Ba(s) + 2H2O(l)  Ba(OH)2(aq) + H2(g); Single-Displacement Reaction
d. Cl2(g) + 2KBr(aq)  2KCl(aq) + Br2(l); Single-Displacement Reaction
𝑃𝑡
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e. 4NH3(g) + 5O2(g) → 4NO(g) + 6H2O(l); Combustion Reaction (Ex. Without Carbon)
f. 2H2O(l)  2H2(g) + O2(g); Decomposition Reaction
a. Cu(s) + Cl2(g)  CuCl2(s); Synthesis Reaction
b. Ca(ClO3)2(s)  CaCl2(s) + 3O2(g); Decomposition Reaction
c. 2Li(s) + 2H2O(l) 2LiOH(aq) + H2(g); Single-Displacement Reaction
d. PbCO3(s) PbO(s) + CO2(g); Decomposition Reaction
12.3 mol HCl
H2O
a. nothing, 2, nothing, 2
b. nothing, 12, 12, 11
c. 2, 3, nothing, 6