1. Which compound has both ionic and covalent bonds? CO2 CH3OH NaI Na2CO3 2. Which group on the Periodic Table of the Elements contains elements that react with oxygen to form compounds with the general formula X 20? Group 1 Group 14 Group 18 3. What is the total number of different elements present in? 7 9 3 4 4. Element X reacts with iron to form two different compounds with the formulas FeX and Fe2X3. To which group on the Periodic Table does element X belong? Group 8 Group 13 Group 16 5. A metal, M, forms an oxide compound with the general formula M2O. In which group on the Periodic Table could metal M be found? Group 1 Group 16 Group 17 6. What is the chemical formula for sodium sulfate? Na2SO3 Na2SO4 NaSO3 NaSO4 7. What is the name of the polyatomic ion in the compound Na2O2? hydroxide oxalate oxide peroxide 8. What is the chemical formula for nickel (II) hypochlorite? NiCl2 Ni(ClO)2 NiClO2 Ni(ClO)3 9. To break a chemical bond, energy must be absorbed destroyed produced released 10. Given the balanced equation representing a reaction: Br2 + energy Br + Br Which statement describes the energy change and bonds in this reaction? Energy is released as bonds are broken. Energy is released as bonds are formed. Energy is absorbed as bonds are broken. Energy is absorbed as bonds are formed. 11. Given the reaction: Cl(g) + Cl(g) Cl2(g) + energy Which statement best describes the reaction? A bond is formed and energy is absorbed. A bond is formed and energy is released. A bond is broken and energy is absorbed. A bond is broken and energy is released. 12. Which symbol represents an atom in the ground state with the most stable valence electron configuration? B O Li Ne 13. Given the Lewis electron-dot diagram: Which electrons are represented by all of the dots? the carbon valence electrons, only the hydrogen valence electrons, only the carbon and hydrogen valence electrons all of the carbon and hydrogen electrons 14. Which is the correct electron-dot formula for a molecule of chlorine? 15. What is the most likely electronegativity value for a metallic element? 1.3 2.7 3.4 4.0 16. Which element has an atom with the greatest tendency to attract electrons in a chemical bond? carbon chlorine 17. Which bond is least polar? silicon sulfur As Cl Bi Cl P Cl N Cl 18. Given the electron dot diagram: The electrons in the bond between hydrogen and fluorine are more strongly attracted to the atom of hydrogen, which has the higher electronegativity fluorine, which has the higher electronegativity hydrogen, which has the lower electronegativity fluorine, which has the lower electronegativity Page 1
19. Which element forms an ionic compound when it reacts with lithium? 27. A chemist performs the same tests on two homogeneous white crystalline solids, A and B. The results are shown in the table below. K Fe Kr Br 20. The bonds in BaO are best described as covalent, because valence electrons are shared covalent, because valence electrons are transferred ionic, because valence electrons are shared ionic, because valence electrons are transferred 21. Which of the following solids has the highest melting point? H2O(s) Na2O(s) SO2(s) CO2(s) 22. A student determined the solubility of an unknown solid in various solvents as shown in the table below. The results of these tests suggest that both solids contain only ionic bonds both solids contain only covalent bonds solid A contains only covalent bonds and solid B contains only ionic bonds solid A contains only ionic bonds and solid B contains only covalent bonds 28. The high electrical conductivity of metals is primarily due to high ionization energies filled energy levels 29. Metallic bonding occurs between atoms of mobile electrons high electronegativities Based on these solubility results, the unknown solid is best described as ionic nonpolar nonpolar covalent coordinate covalent network metallic 23. Which type of bonding is characteristic of a substance that has a high melting point and electrical conductivity only in the liquid phase? one pair of electrons one pair of protons ionic metallic 24. The nitrogen atoms in a molecule of N2 share a total of 25. Given a formula for oxygen: three pairs of electrons three pairs of protons What is the total number of electrons shared between the atoms represented in this formula? 1 2 8 4 26. Given the formula of a substance: sulfur copper fluorine carbon 30. Which molecule has a nonpolar covalent bond? 31. Which electron-dot formula represents a substance that contains a nonpolar covalent bond? 32. Which statement explains why a CO2 molecule is nonpolar? Carbon and oxygen are both nonmetals. Carbon and oxygen have different electronegativities. The molecule has a symmetrical distribution of charge. The molecule has an asymmetrical distribution of charge. 33. Given the formula representing a molecule: H C C H The molecule is What is the total number of shared electrons in a molecule of this substance? 22 11 9 6 symmetrical and polar symmetrical and nonpolar asymmetrical and polar asymmetrical and nonpolar Page 2
Base your answers to questions 34 and 35 on the information below and on your knowledge of chemistry. Silver-plated utensils were popular before stainless steel became widely used to make eating utensils. Silver tarnishes when it comes in contact with hydrogen sulfide,, which is found in the air and in some foods. However, stainless steel does not tarnish when it comes in contact with hydrogen sulfide. 34. In the ground state, an atom of which noble gas has the same electron configuration as the sulflde ion in? 35. Draw a Lewis electron-dot diagram for the compound that tarnishes silver. Base your answers to questions 36 and 37 on the information below and on your knowledge of chemistry. Before atomic numbers were known, Mendeleev developed a classification system for the 63 elements known in 1872, using oxide formulas and atomic masses. He used an R in the oxide formulas to represent any element in each group. The atomic mass was listed in parentheses after the symbol of each element. A modified version of Mendeleev's classification system is shown in the table below. 36. Explain, in terms of chemical reactivity, why the elements in Group 18 on the modern Periodic Table were not identified by Mendeleev at that time. 37. Based on Mendeleev's oxide formula, what is the number of electrons lost by each atom of the elements in Group III? 38. Explain, in terms of electronegativity difference, why the bond in a molecule of HF is more polar than the bond in a molecule of HI. 39. Explain, in terms of valence electrons, why the bonding in magnesium oxide, MgO, is similar to the bonding in barium chloride, BaCl2. 40. Base your answer to the following question on the information below. At STP, iodine, I2, is a crystal, and fluorine, F2, is a gas. Iodine is soluble in ethanol, forming a tincture of iodine. A typical tincture of iodine is 2% iodine by mass. Draw a Lewis electron-dot diagram for a molecule of I2. Page 3
Base your answers to questions 41 and 42 on the information below. The particle diagrams below represent the reaction between two nonmetals, A2 and Q2. 41. Identify the type of chemical bond between an atom of element A and an atom of element Q. 42. Using the symbols A and Q, write the chemical formula of the product. 43. Draw a Lewis electron-dot diagram for a molecule of phosphorus trichloride, PCl3 Page 4
Answer Key PRACTICE Exam 2015 1. 4 2. 1 3. 3 4. 4 5. 1 6. 2 7. 4 8. 2 9. 1 10. 3 11. 2 12. 4 13. 3 14. 4 15. 1 16. 2 17. 4 18. 2 19. 4 20. 4 21. 2 22. 1 23. 3 24. 3 25. 4 26. 1 27. 4 28. 3 29. 2 30. 1 31. 2 32. 3 33. 2 34. Ar argon element 18 35. 36. Since the Group 18 elements tend not to react with other elements, there were no oxide compounds for Mendeleev to study. Group 18 elements are generally unreactive. 37. three electrons three 3 38. Acceptable responses include, but are not limited to: The electronegativity difference between H and F is greater than the electronegativity difference between H and I. The difference for HF is 1.9, and the difference for HI is 0.6. 39. The bonding in each compound involves a transfer of valence electrons from the metal to the nonmetal. Both metals lose all of their valence electrons. 40. 41. Examples: polar covalent covalent 42. Examples: AQ2 Q2A 43. Page 5