ExamView - Study guide questions for Chapter 7

Name: ________________________ Class: ___________________ Date: __________

ID: A

Study Guide For Chapter 7

Multiple Choice

Identify the choice that best completes the statement or answers the question.

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1. The number of atoms in a mole of any pure substance is called

a. its atomic number.

c. its mass number.

b. Avogadro¡¯s number.

d. its gram-atomic number.

2. What can be said about 1 mol Ag and 1 mol Au?

a. They are equal in mass.

b. They contain the same number of atoms.

c. Their molar masses are equal.

d. They have the same atomic mass.

3. An Avogadro¡¯s number of any element is equivalent to

a. the atomic number of that element.

c. 6.022 ¡Á 1023 particles.

b. the mass number of that element.

d. 12 g of that element.

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4. If 0.500 mol of Na combines with 0.500 mol of Cl¨C to form NaCl, how many formula units of NaCl are

present?

a. 3.01 ¡Á 1023

c. 6.02 ¡Á 1024

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b. 6.02 ¡Á 10

d. 1.00

5. Using a periodic table, what is the average atomic mass of zinc?

a. 69.723 amu

c. 63.546 amu

b. 58.693 amu

d. 65.39 amu

6. The atomic mass of hydrogen is 1.008 amu. The reason that this value is not a whole number is that

a. hydrogen only exists as a diatomic molecule.

b. the mass of hydrogen is the sum of the masses of the protons and electrons in the atom.

c. the mass of a proton is not exactly equal to 1 amu.

d. hydrogen has more than one isotope.

7. A chemical formula includes the symbols of the elements in the compound and subscripts that indicate

a. the number of formula units present.

b. the number of atoms or ions of each type.

c. the formula mass.

d. the charges on the elements or ions.

8. How many atoms of fluorine are in a molecule of carbon tetrafluoride, CF 4?

a. 1

c. 4

b. 2

d. 5

9. Changing a subscript in a correctly written chemical formula

a. changes the number of moles represented by the formula.

b. changes the charges on the other ions in the compound.

c. changes the formula so that it no longer represents that compound.

d. has no effect on the formula.

10. A formula that shows the simplest whole-number ratio of the atoms in a compound is the

a. molecular formula.

c. structural formula.

b. ideal formula.

d. empirical formula.

11. The molar mass of an element is the mass of one

a. atom of the element.

c. gram of the element.

b. liter of the element.

d. mole of the element.

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Name: ________________________

ID: A

____ 12. To determine the molar mass of an element, one must know the element¡¯s

a. Avogadro number.

c. number of isotopes.

b. atomic number.

d. average atomic mass.

____ 13. What is the molar mass of magnesium?

a. 12.00 g

c. 24.305 g

b. 26.982 g

d. 22.990 g

____ 14. 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

____ 15. What is the empirical formula for a compound that is 43.6% phosphorus and 56.4% oxygen?

c. P2O3

a. P3O7

b. PO3

d. P2O5

____ 16. What is the empirical formula for a compound that is 53.3% O and 46.7% Si?

a. SiO

c. Si2O

d. Si2O3

b. SiO2

____ 17. 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

d. CF2

b. C4F

____ 18. A compound contains 64 g of O and 4 g of H. What is the empirical formula for this compound?

a. H2O

c. H4O4

b. H2O2

d. HO

____ 19. 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

____ 20. 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

d. C2O4

b. CO2

____ 21. To find the molecular formula from the empirical formula, one must determine the compound¡¯s

a. density.

c. structural formula.

b. formula mass.

d. crystal lattice.

____ 22. A molecular compound has the empirical formula XY3. Which of the following is a possible molecular

formula?

a. X2Y3

c. X2Y5

b. XY4

d. X2Y6

____ 23. The molecular formula for vitamin C is C6H8O6. What is the empirical formula?

a. CHO

c. C3H4O3

b. CH2O

d. C2H4O2

____ 24. A compound¡¯s empirical formula is NO2. If the formula mass is 92 amu, what is the molecular formula?

a. NO

c. NO2

b. N2O2

d. N2O4

____ 25. 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

____ 26. What is the percentage composition of CuCl 2?

a. 33% Cu, 66% Cl

c. 65.50% Cu, 34.50% Cl

b. 50% Cu, 50% Cl

d. 47.267% Cu, 52.733% Cl

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Name: ________________________

ID: A

____ 27. The percentage of sulfur in SO2 is about 50%. What is the percentage of oxygen in this compound?

a. 25%

c. 75%

b. 50%

d. 90%

____ 28. What is the percentage of OH¨C in Ca(OH)2?

a. 45.9%

c. 75%

b. 66.6%

d. 90.1%

Completion

Complete each statement.

29. As the atomic masses of the elements in the periodic table decreases, the number of atoms in one mole of the

element ____________________.

30. The unit used for counting numbers of atoms, ions, or molecules is the ____________________.

31. If you have 1.204 ¡Á 1024 atoms of nickel, you have ____________________ as the amount of nickel.

32. The number of eggs is to the number of dozens as the number of particles is to the number of

____________________.

33. In one mole of carbon dioxide, CO 2, there are ____________________ oxygen atoms.

34. For sodium, the conversion factor that is used to change mass to moles is ____________________.

35. For potassium, the conversion factor that is used to change moles to mass is ____________________.

36. The conversion factor used to change moles to number of particles is ____________________.

37. The element that has an atomic mass of 40.078 amu is ____________________.

38. The average atomic mass of cobalt is ____________________.

39. Comparing the average atomic masses of copper and zinc, the average atomic mass of

____________________ is larger.

40. The empirical formula is always the accepted formula for a(n) ____________________.

41. The empirical formula for a compound shows the symbols of the elements with subscripts indicating the

____________________.

42. In one mole of acetic acid, CH3COOH, there are ____________________ moles of hydrogen atoms.

43. Two moles of carbon atoms are present in ____________________ of C 6H6.

44. The unit used for molar mass is ____________________.

45. The molar mass of gallium is ____________________.

46. The molar mass of magnesium oxide, MgO, is ____________________.

47. The molar mass of barium nitrate, Ba(NO3)2, is ____________________.

48. The first step in finding an empirical formula from percentage composition is to assume that you have

____________________ grams of sample.

49. To find an empirical formula from percentage composition, you must divide the number of grams of each

element by that element¡¯s ____________________.

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Name: ________________________

ID: A

50. If, in determining the empirical formula from percentage composition, your first subscripts show the formula

to be Fe1O1.3, you must ______________________________ to obtain the final subscripts.

51. The empirical formula and the formula mass of a compound are needed to determine the compound¡¯s

____________________.

52. A compound¡¯s empirical formula is N2O5. If the formula mass is 108 amu, its molecular formula is

____________________.

53. A compound¡¯s empirical formula is CH3. If the formula mass is 30 amu, its molecular formula is

____________________.

54. To calculate the percentage composition of NiCl2, you need to know ____________________.

55. The percentage of oxygen in NaOH is ____________________.

56. The percentage of sulfur in ammonium sulfate, (NH4)2SO4, is ____________________.

Short Answer

57. Explain the relationship among 6.022 ¡Á 1023, one mole, and 12.01 g of carbon.

58. Why will one mole of copper(II) chloride give you more chloride ions than one mole of copper(I) chloride?

59. Explain how you would determine the number of moles of aluminum in 96.7 g of aluminum.

60. Explain how you would calculate the mass in grams of one sodium atom.

61. Describe atomic mass.

62. Describe the atomic mass unit.

63. How are the atomic mass unit and the atomic mass related?

64. Why is the formula for ammonium sulfate written as (NH4)2SO4 and not as N2H8SO4?

65. A student was supposed to find the molar mass of calcium nitrate, Ca(NO3)2. She added the molar masses of

calcium, nitrogen, and oxygen. Explain why she did not get the correct value for the molar mass of the

compound.

66. Explain the term empirical formula. What is the empirical formula of strontium bromide, SrBr2?

67. You have samples of two compounds. Both contain only iron and chlorine. Explain what you would need to

know to determine whether the two samples are the same compound or not.

68. Describe the steps used when determining a molecular formula, given an empirical formula and the molecular

mass.

69. Explain how to calculate the percentage of aluminum in AlF 3. What is the percentage of Al in AlF3?

Problem

70. The mass of 1 mol of gold atoms is 196.97 g. Find the mass of 1 atom of gold.

71. You have 1.6 ¡Á 1021 molecules of oxygen gas, O2. What is the mass of that number of molecules?

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Name: ________________________

ID: A

72. What is the mass of 2.5 moles of carbon?

73. How many moles of copper are present in 180.0 g Cu?

74. How many moles of oxygen atoms are present in 2.0 grams of oxygen gas, O 2?

75. Argentite is a silver ore that contains 87% silver and 13% sulfur. What is the empirical formula for argentite?

76. Calculate the percentage of sulfur in CuSO4.

77. Calculate the percentage of oxygen in Fe 2SiO4.

78. Calculate the percentage of aluminum in Al2O3.

Essay

79. How can you count the number of atoms in a sample of a compound by using a balance?

80. Explain how a chemical formula is related to the mole.

81. Explain how a molecular formula is related to an empirical formula.

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