1. 1 Mg, 2 O, and 2 H
2 Mg, 2 O, and 2 H
6 Mg, 6 O, and 6 H
3 Mg, 6 O, and 6 H

2. 1 Mg, 2 O, and 2 H
2 Mg, 2 O, and 2 H
6 Mg, 6 O, and 6 H
3 Mg, 6 O, and 6 H

3.   NaS
  NaS2
  Na2S 
  Na2S2

4.   NaS
  NaS2
  Na2S 
  Na2S2

5.  too few significant figures are used in the problem’s calculations.
there are experimental uncertainties in the measurements.
 coefficients are always rounded to integers so it doesn’t matter.
 approximations were made in the calculations.

6.  too few significant figures are used in the problem’s calculations.
there are experimental uncertainties in the measurements.
 coefficients are always rounded to integers so it doesn’t matter.
 approximations were made in the calculations.

7. 1.57 mol H2 reacts.
0.785 mol H2 reacts.
Cannot be determined without more information.
3.14 mol H2 reacts.

8. 1.57 mol H2 reacts.
0.785 mol H2 reacts.
Cannot be determined without more information.
3.14 mol H2 reacts.

9. The following equation is unbalanced:
CS2 + O CO2 + SO2
What is the correct balanced equation?
CS2 + 2 O2 → CO2 + 2 SO2
2 CS O2 → 2 CO2 + 4 SO2
CS2 + 3 O2 → CO2 + 2 SO2
CS2 + 6 O2 → CO2 + 2 SO2

10. Correct Answer: CS2 + 2 O2 → CO2 + 2 SO2 2 CS2 + 12 O2 → 2 CO2 + 4 SO2
This is the only case where the number of each type of atom is the same on both the reactant and product sides of the equation.

11. Which of the following is the correct, balanced chemical equation for the combustion of ethanol (C2H5OH)?
C2H5OH + O2 → CO2 + H2O
C2H5OH + 3 O2 → 2 CO2 + 3 H2O
C2H5OH + 6 O2 → 4 CO2 + 6 H2O
2 C2H5OH + 7 O2 → 4 CO2 + 6 H2O O O O C

12. Correct Answer: C2H5OH + O2 → CO2 + H2O C2H5OH + 3 O2 → 2 CO2 + 3 H2O

13. If the empirical formula of a compound is C2H2N but the molecular weight is
160 g/mol, what is the molecular formula?
C2H2N
C4H4N2
C6H8N3
C8H8N4
None of the above choices is correct.

14. Correct Answer: C2H2N C4H4N2 C6H8N3 C8H8N4
None of the above choices is correct.
FW C2H2N = ( ) g/mol = 40 g/mol
MW/FW = 160/40 = 4
Thus, molecular formula is 4 empirical formula 4(C2H2N) = C8H8N4

15. How many fluorine atoms are present in 2.0 moles of AlF3?
3.0  1023
6.0  1023
1.2  1024
3.6  1024
None of the above answers is correct.

16. Correct Answer:
3.0  1023
6.0  1023
1.2  1024
3.6  1024
None of the above answers is correct.
(2.0 moles AlF3)(6.0  1023 molecules AlF3/mole AlF3) (3 atoms F/1 molecule AlF3) = 3.6  1024

17. Which of the following samples has the largest number of atoms?
28 g Si
28 g CO
28 g N2
15 g C2H4
All of the above have equal numbers of atoms.

18. Correct Answer: 28 g Si 28 g CO 28 g N2 15 g C2H4
All of the above have equal numbers of atoms.
28 g Si has 1 mole of atoms, whereas 28 g of CO and N2 have 2 moles of atoms, even though they also have only 1 mole substance. However, there are 6 atoms for every 1 mole of C2H4, so in this case there are slightly more than 3 moles worth of atoms.

19. The molecular mass for the compound, XClO3, is 122. 5 amu
The molecular mass for the compound, XClO3, is amu. The atomic mass of X is equal to ____ amu, which is the element ____.
1.0; H
6.9; Li
23.0; Na
39.1; K
85.5; Rb

20. MW = 122.5 amu = AW X + AW Cl + 3(AW O)
Correct Answer:
1.0; H
6.9; Li
23.0; Na
39.1; K
85.5; Rb
MW = amu = AW X + AW Cl + 3(AW O)
122.5 amu  AW Cl  3 (AW O) = AW X
122.5 amu  (35.45 amu)  3 (16.0 amu) = AW X
122.5  amu  48.0 amu = AW X
AW X = 39.1 amu

21. When the chemical equation, C4H10(g) + O2(g) H2O(g) + CO2(g),
is balanced, the stoichiometric coefficients are, respectively:
1, 4, 5, 4
2, 13, 10, 8
2, 9, 8, 10
2, 7, 4, 5

22. Correct Answer:
1, 4, 5, 4
2, 13, 10, 8
2, 9, 8, 10
2, 7, 4, 5

23. CH4(g) + 2 O2(g) 2 H2O(l) + CO2(g)
The combustion of methane (CH4) is shown below:
CH4(g) + 2 O2(g) H2O(l) + CO2(g)
How many grams of water are produced in the combustion of 1.0 moles of methane?
16 g
32 g
36 g
48 g

24. Correct Answer:
16 g
32 g
36 g
48 g
(1.0 mole CH4)(2 moles H2O/1 mole CH4)(18 g H2O/1 mole H2O)
= 36 g

25. There is a molar excess of carbon, not all carbon is consumed.
0.5 mol of carbon is combusted with 1.0 mol of oxygen gas. Which of the following statements is correct?
There is a molar excess of carbon, not all carbon is consumed.
There is a molar excess of oxygen, not all oxygen is consumed.
There are stoichiometrically equivalent amounts of carbon and oxygen gas.

26. Correct Answer:
There is a molar excess of carbon, not all carbon is consumed.
There is a molar excess of oxygen, not all oxygen is consumed.
There are stoichiometrically equivalent amounts of carbon and oxygen gas.
C and O2 react in a 1:1 stoichiometric ratio, therefore there must be excess O2 because there was a larger initial number of moles of it.

27. 0.5 mol of carbon is combusted with
1.0 mol g of oxygen gas. How many moles of carbon dioxide are produced?
1.5 mol
1.0 mol
0.5 mol
2.0 mol

28. Correct Answer: 1.5 mol 1.0 mol 0.5 mol 2.0 mol
C and O2 react in a 1:1 stoichiometric ratio, therefore C must be the limiting reagent and O2 must be the excess reagent. Initially,
(0.5 moles C)(1 mole CO2/1 mole C) = 0.5 mole CO2

29. 24.0 g of carbon are combusted with
32.0 g of oxygen gas. How many grams of carbon dioxide are produced?
56.0 g
88.0 g
28.0 g
44.0 g

30. Correct Answer:
56.0 g
88.0 g
28.0 g
44.0 g
C and O2 react in a 1:1 stoichiometric ratio. Initially,
(24.0 g C)  (1 mole C/12.0 g C)  (1 mole CO2/1 mole C) = 2.0 mole CO2
(32.0 g O2)  (1 mole O2/32.0 g O2)  (1 mole CO2/1 mole O2) = 1.0 mole CO2
Thus, O2 is limiting, and 1.0 mole of CO2 is 44.0 g.

31. 3. 0 moles Mg are combusted with 2. 0 moles O2
3.0 moles Mg are combusted with 2.0 moles O2. What is the limiting reagent and how many moles of the excess reagent remain?
Magnesium, 0.5 mole
Magnesium, 1.0 mole
Oxygen gas, 0.5 mole
Oxygen gas, 1.0 mole

32. Correct Answer: Magnesium, 0.5 mole Magnesium, 1.0 mole
Oxygen gas, 0.5 mole
Oxygen gas, 1.0 mole
Mg and O2 react in a 2:1 stoichiometric ratio. Initially,
(3 mole Mg)(2 mole MgO/2 mole Mg)
= 1.5 mole MgO
(2 mole O2)(2 mole MgO/1 mole O2) = 4 mole MgO
Thus, Mg is limiting, and 3 mol Mg will consume 1.5 mol of O2, leaving 0.5 mole of O2.

33. How many oxygen atoms are present in MgSO4 • 7 H2O?

34. How many oxygen atoms are present in MgSO4 • 7 H2O?

35. How many sulfur atoms are present in 1.0 mole of Al2(SO4)3?
6.0 x 1023 sulfur atoms
1.8 x 1024 sulfur atoms

36. How many sulfur atoms are present in 1.0 mole of Al2(SO4)3?
6.0 x 1023 sulfur atoms
1.8 x 1024 sulfur atoms

37. If you have equal masses of the following metals, which will have the most number of atoms?
Lithium
Sodium
Potassium
Rubidium
Calcium
An alkali metal
Ca in H2O

38. If you have equal masses of the following metals, which will have the most number of atoms?
Lithium
Sodium
Potassium
Rubidium
Calcium
An alkali metal
Ca in H2O

39. How many moles of oxygen gas are required to react completely with 1
How many moles of oxygen gas are required to react completely with 1.0 mole NO?
2 NO (g) O2 (g) NO2 (g)
0.5 mol O2
1.0 mol O2
1.5 mol O2
2.0 mol O2
2.5 mol O2

40. How many moles of oxygen gas are required to react completely with 1
How many moles of oxygen gas are required to react completely with 1.0 mole NO?
2 NO (g) O2 (g) NO2 (g)
0.5 mol O2
1.0 mol O2
1.5 mol O2
2.0 mol O2
2.5 mol O2

41. If 10. 0 moles of NO are reacted with 6
If 10.0 moles of NO are reacted with 6.0 moles O2, how many moles NO2 are produced?
2 NO (g) O2 (g) NO2 (g)
2.0 mol NO2
6.0 mol NO2
10.0 mol NO2
16.0 mol NO2
32.0 mol NO2

42. If 10. 0 moles of NO are reacted with 6
If 10.0 moles of NO are reacted with 6.0 moles O2, how many moles NO2 are produced?
2 NO (g) O2 (g) NO2 (g)
2.0 mol NO2
6.0 mol NO2
10.0 mol NO2
16.0 mol NO2
32.0 mol NO2

43. If you have equal concentrations of the following aqueous solutions, which will have the highest conductivity?
CaCl2
KBr
Na2SO4
Al(NO3)3
LiC2H3O2

44. If you have equal concentrations of the following aqueous solutions, which will have the highest conductivity?
CaCl2
KBr
Na2SO4
Al(NO3)3
LiC2H3O2

45. Which mixture will produce a precipitate?NH 3
+ HF
HClO 4
+ KOH Na 2 SO
+ PbCl
Ca(NO )
+ KC H O
(NH CO
+ Na PO

46. Which mixture will produce a precipitate?NH 3
+ HF
HClO 4
+ KOH Na 2 SO
+ PbCl
Ca(NO )
+ KC H O
(NH CO
+ Na PO

47. What is(are) the spectator ion(s) in the following reaction?
KOH (aq) + HF (aq) KF (aq) + H2O (l) K+ F-
K+ and F-
OH- and H+
OH-

48. What is(are) the spectator ion(s) in the following reaction?
KOH (aq) + HF (aq) KF (aq) + H2O (l) K+ F-
K+ and F-
OH- and H+
OH-

49. Which of the following reactions has the net ionic equation:
H+ (aq) OH- (aq) H2O (l)
Reaction 1
Reactions 1, 4
Reactions 2, 3
Reactions 2, 4
Reactions 3, 4

50. Which of the following reactions has the net ionic equation:
H+ (aq) OH- (aq) H2O (l)
Reaction 1
Reactions 1, 4
Reactions 2, 3
Reactions 2, 4
Reactions 3, 4

51. Which will have the highest concentration of Na+?
0.35 M Na2SO4
0.40 M Na3PO4
0.50 M NaNO3
0.80 M NaOH
1.00 M NaCl

52. Which will have the highest concentration of Na+?
0.35 M Na2SO4
0.40 M Na3PO4
0.50 M NaNO3
0.80 M NaOH
1.00 M NaCl

53. Given the following reactions, rank the activity of each metal.
Mg>Al>Zn>Cu
Al>Mg>Zn>Cu
Cu>Zn>Al>Mg
Zn>Cu>Al>Mg
Al>Mg>Cu>Zn

54. Given the following reactions, rank the activity of each metal.
Mg>Al>Zn>Cu
Al>Mg>Zn>Cu
Cu>Zn>Al>Mg
Zn>Cu>Al>Mg
Al>Mg>Cu>Zn

55. Which of the following substances would be considered a nonelectrolyte?
Methanol, CH3OH
Hydrofluoric acid, HF
Sulfuric acid, H2SO4
Sodium hydroxide, NaOH

56. Correct Answer: Methanol, CH3OH Hydrofluoric acid, HF
Sulfuric acid, H2SO4
Sodium hydroxide, NaOH
Methanol is an organic molecule that does not form ions in solution.

57. Which ions are spectator ions in the reaction represented by the following molecular equation?
AgNO3(aq) + NaCl(aq)  AgCl(s) + NaNO3(aq)
Na+ and NO3
Na+ and Cl
Ag+ and Cl
Ag+ and NO3

58. Correct Answer: Na+ and NO3 Na+ and Cl Ag+ and Cl Ag+ and NO3
Spectator ions are present, but play no direct role in the reaction.

59. Which of the following is not an oxidation-reduction reaction?
CH4(g) + 2 O2(g)  CO2(g) + 2 H2O(g)
HCl(aq) + Zn(s)  ZnCl2(aq) + H2(g)
Ca(OH)2(aq) + 2 HCl(aq)  CaCl2(aq) + 2 H2O(l)
Fe2O3(s) + 3 H2(g)  2 Fe(s) + 3 H2O(l)

60. Correct Answer: CH4(g) + 2 O2(g)  CO2(g) + 2 H2O(g)
HCl(aq) + Zn(s)  ZnCl2(aq) + H2(g)
Ca(OH)2(aq) + 2 HCl(aq)  CaCl2(aq) + 2 H2O(l)
Fe2O3(s) + 3 H2(g)  2 Fe(s) + 3 H2O(l)
This is an acid-base reaction, and no species change oxidation state.

61. What is the oxidation state of sulfur in the compound SF2?+2 +4 2 4

62. Correct Answer: +2 +4 2 4
Because F is 1, and there are two F atoms, S must be +2.

63. What is the oxidation state of nitrogen in the compound N2O5?+1 +2 +5 3

64. Correct Answer: +1 +2 +5 3
Because O is 2, and there are five O atoms, each of the two N atoms must be +5.

65. Which of the following compounds contains a chlorine atom with an oxidation number of +5?
ClF5
KClO4
HCl
Cl2

66. Correct Answer: ClF5 KClO4 HCl Cl2
Because F is 1, and there are five F atoms, the Cl atom must be +5.
Structure of ClF5 is to the left.

67. A 80.0 mL solution of sodium chloride at 1.00 M is to be diluted to M. What is the total volume of the diluted solution? L
0.720 L L
0.800 L
MdiluteVdilute = moles = MconcVconc

68. Correct Answer: L
0.720 L L
0.800 L
0.100 M(Vdilute) = (1.00 M)(80.0 mL)
Vdilute = (1.00 M)(80.0 mL)/0.100 M
Vdilute = 800. mL, or L

69. How many moles of phosphoric acid, H3PO4, are needed to prepare 2
How many moles of phosphoric acid, H3PO4, are needed to prepare 2.00 L of a 0.75 M phosphoric acid solution?
4.0 moles
1.5 moles
1.8 moles
0.75 moles

70. How many moles of phosphoric acid, H3PO4, are needed to prepare 2
How many moles of phosphoric acid, H3PO4, are needed to prepare 2.00 L of a 0.75 M phosphoric acid solution?
4.0 moles
1.5 moles
1.8 moles
0.75 moles

71. A 50.0 mL solution of HCl at 1.00 M is to be titrated with a solution of 2.50 M NaOH. How many mL of NaOH are required to reach the equivalence point?
20.0 mL
125 mL
50.0 mL
70.0 mL

72. 0.0500 mol acid(1 mol base/1 mol acid)
Correct Answer:
20.0 mL
125 mL
50.0 mL
70.0 mL
(50.0 mL HCl)(1.00 M) = mol acid
mol acid(1 mol base/1 mol acid)
= mol base
Vbase = mol/M = mol/2.50M
= L or mL

73. A 50.0 mL solution of H2SO4 at 1.00 M is to be titrated with a solution of M NaOH. How many mL of NaOH are required to reach the equivalence point?
100. mL
200. mL
300. mL
50.0 mL

74. 0.0500 mol acid(2 mol base/1 mol acid)
Correct Answer:
100. mL
200. mL
300. mL
50.0 mL
(50.0 mL H2SO4)(1.00 M) = mol acid
mol acid(2 mol base/1 mol acid)
= mol base
Vbase = mol/M = mol/0.500M
= L or mL

75. KCN(aq)
K+(aq) and CN–(aq)
K–(aq) and CN+(aq)
K+(aq), C4–(aq), and N3+(aq)

76. KCN(aq)
K+(aq) and CN–(aq)
K–(aq) and CN+(aq)
K+(aq), C4–(aq), and N3+(aq)

77. NaClO4(aq)
Na+(aq) and 4ClO–(aq)
Na+(aq), Cl–(aq) and 4O2–(aq)
Na+(aq) and ClO4–(aq)

78. NaClO4(aq)
Na+(aq) and 4ClO–(aq)
Na+(aq), Cl–(aq) and 4O2–(aq)
Na+(aq) and ClO4–(aq)

79. Cannot determine without concentration information.
Both will cause the lightbulb to glow with equal brightness.
MgBr2
CH3OH

80. Cannot determine without concentration information.
Both will cause the lightbulb to glow with equal brightness.
MgBr2
CH3OH

81. Cannot determine without concentration information.
HBr
H2SO3
HC2H3O2

82. Cannot determine without concentration information.
HBr
H2SO3
HC2H3O2

83. Concentration (molarity) remains the same.
The new concentration is 0.25 M.
The new concentration is 1.00 M.
The new concentration is 2.00 M.

84. Concentration (molarity) remains the same.
The new concentration is 0.25 M.
The new concentration is 1.00 M.
The new concentration is 2.00 M.

85. 12.50 mL
25.00 mL
50.00 mL
75.00 mL

86. 12.50 mL
25.00 mL
50.00 mL
75.00 mL