Chem A Practice Exam f2013

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1 Class: Date: Chem A Practice Exam f2013 Short Answer 1. The following length measurements were taken by students using several different measuring devices. Find the average of the measurements. Make sure that your answer has the correct number of significant figures cm, 10.1 cm, cm, 10.6 cm, 10.5 cm 2. Round off the measurement m to three significant figures. 3. What is the sum of L and 3 L expressed in the correct number of significant digits? 4. What is the product of the number 1000 and the measurement m expressed in the correct number of significant digits? 5. The mass of the electron is kg. Express the mass of the electron to 1, 2, 3, and 4 significant figures. 6. Express 0.05 grams in kilograms, using the correct abbreviations. 7. What is the density of an object having a mass of 4.0 g and a volume of 39.0 cubic centimeters? 8. A cube of a gold-colored metal with a volume of 59 cm 3 has a mass of 980 g. The density of pure gold is 19.3 g/cm 3. Is the metal pure gold? Show calculations to justify your answer. 9. List the number of protons, neutrons, and electrons in 13 6 C. 10. Chlorine has two naturally occurring isotopes, Cl-35 and Cl-37. The atomic mass of chlorine is Which of these two isotopes of chlorine is more abundant? 11. Consider an element Z that has two naturally occurring isotopes with the following percent abundances: the isotope with a mass number of 19.0 is 55.0% abundant; the isotope with a mass number of 21.0 is 45.0% abundant. What is the average atomic mass for element Z? 12. A fictitious element X is composed of 10.0 percent of the isotope 55 X, 20.0 percent of the isotope 56 X, and 70.0 percent of the isotope 57 X. Estimate the atomic mass of element X. 1

2 13. The element chromium has four naturally occurring isotopes. Use the relative abundance of each to calculate the average atomic mass of chromium. 50 Cr = 4.34%, 52 Cr = 83.79%, 53 Cr = 9.50%, 54 Cr = 2.37%. 14. Give the electron configuration for a neutral atom of beryllium. 15. Give the electron configuration for a neutral atom of selenium. 16. Write the electron configuration for chromium. 17. Which group of elements in the periodic table is known as the alkali metals? 18. Which group in the periodic table is known as the noble gases? 19. An element has an atomic number of 80. How many protons and electrons are in an atom of the element? 20. Give the electron configuration for calcium the ion. 21. What is the formula for the oxide ion? 22. Give the electron configuration for the oxide ion. 23. Write the formula for the compound barium oxide. 24. Write the formula for the compound rubidium phosphide. 25. Write the formula for the compound boron chloride. 26. Complete and balance the following equation. Cd(NO 3 + NH 4 Cl 27. Balance the following equation. NaClO 3 NaCl + O Balance the following equation. Mg + H 3 PO 4 Mg 3 (PO 4 + H 2 2

3 29. Balance the following equation. (NH 4 CO 3 + NaOH Na 2 CO 3 + NH 3 + H 2 O 30. Balance the following equation. Complete the equation first, if necessary. Ba + H 2 O Ba(OH + H Balance the following equation. Na 3 PO 4 + ZnSO 4 Na 2 SO 4 + Zn 3 (PO Complete and balance the following equation. Al + Cl Complete and balance the following equation. Fe 2 (SO 4 ) 3 + Ba(OH 34. Complete and balance the following equation: K 3 PO 4 + BaCl What is the electron configuration of oxygen? Modified True/False Indicate whether the statement is true or false. If false, change the identified word or phrase to make the statement true. 36. The speed of light is 3.00 x 10 8 m/s. 37. Every element has a unique characteristic atomic emission spectrum. 38. In the photoelectric effect, photons are ejected from the surface of a metal when light shines on it. 39. The color of visible light that has the shortest wavelength is yellow. 40. The energy of an atom in the excited state is more than its energy in the ground state. 41. If electrons are to occupy the same orbital they must have parallel spins. 3

4 Numeric Response 42. What is the relative charge carried by an electron? 43. What is the relative charge of a proton? 44. Use the periodic table to determine the number of electrons in a neutral atom of lithium. 45. How many protons are present in an atom of Be-9? 46. What is the total number of subatomic particles in the nucleus of an atom of Bi? 47. What is the atomic number for an element with 41 neutrons and a mass number of 80? 48. How many electrons are in an atom of gold? 49. What is the mass number for an oxygen atom that has 10 neutrons in its nucleus? 50. How many protons are present in the nuclei of the three known isotopes of hydrogen? 51. How many neutrons are present in an atom of the isotope U? 52. How many electrons are in the highest occupied energy level of a neutral chlorine atom? 53. How many electrons are in the highest occupied energy level of a neutral strontium atom? 54. How many electrons are in a rubidium ion (Rb + )? 55. What is the usual charge on an ion from Group 7A? 56. How many electrons does the ion Ca 2 + contain? 57. How many valence electrons are in rubidium? 58. How many valence electrons are in bromine? 4

5 59. What is the charge of a particle having 9 protons and 10 electrons? 60. How many electrons does a gallium atom give up when it becomes an ion? 61. What is the total number of covalent bonds normally associated with a single carbon atom in a compound? 62. How many electrons are shared in a single covalent bond? 63. How many electrons does a nitrogen atom need to gain in order to attain a noble-gas electron configuration? 64. How many electrons does carbon need to gain in order to obtain a noble-gas electron configuration? 65. How many electrons are shared in a double covalent bond? 66. What is the charge on the cation in CuSO 4? 67. How many iron(ii) ions combine with oxygen to form iron(ii) oxide? Essay 68. Explain what is meant by a substance and a pure substance. Give an example of each. 69. Define element and compound. Explain the difference between an element and a compound. 70. Discuss the difference between physical changes and chemical changes. Use an example to illustrate the difference. 71. State the law of conservation of mass. Then apply the law to this question: What would be the total mass of the products of a reaction in which 10 grams of water decomposes into the elements hydrogen and oxygen? 72. Explain the difference between precision and accuracy. Suppose you made three different mass measurements of a sugar sample you knew to have a mass of 1 g. How would you know whether or not the measurements were accurate? How would you know whether or not they were precise? Could the three measurements be precise, but not accurate? Explain. 73. Why is the density of a metal greater than the density of water? 74. Explain how the atoms of one element differ from those of another element. 5

6 75. In what way are two isotopes of the same element different? Explain why isotopes of the same element have the same chemical behavior. 76. Describe the shapes and relative energies of the s, p, d, and f atomic orbitals. 77. Describe the different principles that govern the building of an electron configuration. 78. What is the explanation for the discrete lines in atomic emission spectra? 79. Explain what is meant by the Heisenberg uncertainty principle. 80. Describe the trends in the atomic size of elements within groups and across periods in the periodic table. Provide examples. 81. Explain how ions form. Provide examples. 82. Describe the trends in first ionization energy within groups and across periods in the periodic table. Provide examples. 83. Positive ions are smaller than the atoms from which they are formed, but negative ions are larger than the atoms from which they are formed. Explain why this is so. 84. Describe the trends in electronegativity within groups and across periods in the periodic table. Provide examples. 85. Explain the octet rule and give an example of how it is used. 86. Explain how atoms (ions) are held together in an ionic bond. Give an example of an ionic compound. 87. Explain what a polar molecule is. Provide an example. 88. What determines the degree of polarity in a bond? Distinguish between nonpolar covalent, polar covalent, and ionic bonds in terms of relative polarity. 89. Given the name of a binary molecular compound, describe how to write its formula. Use carbon tetrachloride as an example. 90. Name the compounds CuBr 2, SCl 2, and BaF 2. Explain the use or omission of the Roman numeral (II) and the prefix di-. 6

b. Na. d. So. 1 A basketball has more mass than a golf ball because:

b. Na. d. So. 1 A basketball has more mass than a golf ball because: Chem I Semester Review All of the following are general characteristics of a substance in the liquid state except a. definite volume. c. not easily compressed. b. able to flow. d. definite shape. In the