CHEM 101 WINTER 08-09 EXAM III On the answer sheet (Scantron) write you name, student ID number, and recitation section number. Choose the best (most correct) answer for each question and enter it on your answer sheet. Avogadro s Number: 6.022 10 23 mol -1 Speed of Light: c = 3.00 x 10 8 m s -1 Planck s Constant: h = 6.626 x 10-34 J s Rydberg Constant: R = 2.179 x 10-18 J E = hc/λ = hυ q = m c T 1 cal = 4.184 J 1. Please choose the letter a as your answer for this question. 2. The temperature of 3.50 kg of water is raised by 1.17 C when 1.00 g of hydrazine N 2 H 4 is burned in a bomb calorimeter. The calorimeter has a heat capacity of 883 J/ C. How much heat is given off by the sample? a. 0.944 kj b. 16.3 kj c. 17.1 kj d. 18.2 kj e. 21.5 kj 3. Based on the following thermochemical equation below, which statement is false? N 2 (g) + 3 H 2 (g) 2 NH 3 (g) H = 46.11 kj a. For the reverse process, H = + 46.11 kj. b. The value of 46.11 kj applies to the formation of two moles of NH 3. c. The value of 92.22 kj applies to the reaction of two moles of N 2 and three moles of H 2. d. Per mole of N 2, H = 46.11 kj. e. Per mole of H 2, H = 15.37 kj. 4. Determine the heat of reaction for the process TiO 2 (s) + 4HCl(g) TiCl 4 (l) + 2H 2 (g) + O 2 (g) using the information given below: Ti(s) + O 2 (g) TiO 2 (s) H = 939.7 kj 2HCl(g) H 2 (g) + Cl 2 (g) H = 184.6 kj Ti(s) + 2Cl 2 (g) TiCl 4 (l) H = 804.2 kj a. 320.1 kj b. 233.7 kj c. 233.7 kj d. 320.1 kj e. 504.7 kj
5. The standard enthalpies of formation for several substances are given below: CO(g) 110.5 kj/mol CO 2 (g) 393.5 kj/mol H 2 O(l) 285.8 kj/mol H 2 O(g) 241.8 kj/mol H 2 O 2 (l) 187.8 kj/mol CH 3 OH(g) 200.7 kj/mol C 2 H 5 OH(l) 277.7 kj/mol C 2 H 5 OH(g) 235.1 kj/mol Determine the heat of vaporization for H 2 O and C 2 H 5 OH. a. 241.8 and 235.1 kj b. 241.8 and 325.1 kj c. 44.0 and 42.6 kj d. 54.0 and 42.6 kj e. 44.0 and 42.6 kj 6. The standard enthalpies of formation for several substances are given below: FeS 2 (s) = 178.2 kj/mol FeCl 2 (s) = 341.8 kj/mol FeCl 3 (s) = 399.5 kj/mol HCl(g) = 92.3 kj/mol HCl(aq) = 167.1 kj/mol H 2 S(g) = 20.6 kj/mol H 2 O(g) = 271.8 kj/mol Calculate the H for the reaction below. 2FeCl 2 (s) + 2HCl(g) 2FeCl 3 (s) + H 2 (g) a. 219.0 kj b. 69.2 kj c. 34.6 kj d. 69.2 kj e. 219.0 kj 7. Which traits make for the best fuel? a. low fuel value and high energy density b. high fuel value and low energy density c. weak bonds in the fuel and weak bonds in the combustion products d. weak bonds in the fuel and strong bonds in the combustion products e. strong bonds in the fuel and strong bonds in the combustion products 8. Which statement concerning the interaction between two atoms is incorrect? a. If two atoms are widely separated, there is very little attraction between them. b. When two atoms are one bond length apart, the electrons on one atom are attracted to the nucleus of the other atom. c. When two atoms have very little separation between them, repulsion occurs. d. A covalent bond occurs when electrons are shared between two nuclei. e. As atoms get closer together, their electrons attract each other. 9. Which statement about covalent bonds is false? a. Covalent bonds allow atoms to achieve a filled outermost electron shell. b. Covalent bonds are unreactive. c. Covalent bonds occur in molecular compounds. d. Covalent bonds involve valence electrons. e. Covalent bonds form between non-metal atoms.
10. Which element will have four electrons in its Lewis symbol? a. aluminum b. beryllium c. carbon d. magnesium e. oxygen 11. How many electrons will be in the correctly drawn Lewis Structure for CCl 4? a. 32 b. 74 c. 35 d. 8 e. 11 12. Which of the following statements could not describe a covalent bond? a. The sharing of two electrons between two atoms b. The sharing of four electrons between two atoms c. An electrostatic interaction between two oppositely charged ions d. The sharing of two or more electrons equally between two atoms e. The sharing of two or more electrons unequally between two atoms 13. Determine the number of electrons that the four elements below require to achieve an octet of electrons. nitrogen oxygen carbon fluorine a. 1 3 2 4 b. 3 4 2 2 c. 3 2 4 1 d. 4 3 5 2 e. 5 6 4 7 14. Which statement about hydrocarbons is false? a. Hydrocarbons can be straight-chain alkanes or branch-chain alkanes. b. Methane is the simplest hydrocarbon. c. Saturated hydrocarbons contain only C H and C C single covalent bonds. d. Hydrocarbons contain hydrogen, carbon, and other non-metals, such as oxygen. e. Hydrocarbons can contain carbon atoms joined in a ring. 15. Which molecule does not contain a multiple bond? a. H 2 O 2 b. C 2 H 2 c. CH 2 O d. CO 2 e. O 2 16. Write the correct Lewis dot structure for CCl 2 O. Which statement correctly describes the structure? a. The structure contains 3 single bonds, 1 double bond, and 2 lone pairs. b. The structure contains 3 single bonds, 1 triple bond, and 8 lone pairs. c. The structure contains 2 single bonds, 1 double bond, and 2 lone pairs. d. The structure contains 2 single bonds, 1 double bond and 8 lone pairs. e. The structure contains 1 single bond, 1 triple bond, and 2 lone pairs.
17. Assume all hydrocarbons given are linear. Which compound will contain a double bond? a. C 3 H 6 b. C 6 H 10 c. C 2 H 2 d. CH 4 e. C 5 H 12 18. Which of the following compounds can exhibit cis-trans isomerism? a. CH 2 =CH 2 b. CH 3 CH 3 c. H 2 C=O d. ClHC=CHCl e. Cl 2 C=CH 2 19. Which bond is shortest? a. carbon oxygen single bond b. carbon hydrogen single bond c. hydrogen hydrogen single bond d. carbon carbon double bond e. carbon oxygen triple bond 20. Which bond is strongest? a. carbon nitrogen triple bond b. carbon nitrogen double bond c. carbon hydrogen bond d. carbon oxygen triple bond e. carbon carbon single bond 21. Which bond is least polar? a. C C b. C N c. N H d. C F e. C O 22. Which element is the most electronegative? a. sulfur b. iodine c. nitrogen d. aluminum e. carbon 23. What is the formal charge on carbon in HCN? a. 2 b. 1 c. 0 d. +1 e. +2
24. Which of the following species does not have resonance structures? a. CO b. SO 2 c. H 2 O d. NO e. O 3 25. Write the singly bonded Lewis dot structure for BF 3. Which of the following statements best describes this structure? a. It obeys the octet rule on all atoms. b. It has less than an octet on at least one atom. c. It has a lone pair of electrons on the boron atom. d. It has less than an octet of electrons on all atoms. e. It exceeds the octet rule. 26. A list of non-metals is given below. Which entire set of elements cannot exceed the octet rule? B Si N P O S F Cl a. Si, P, S, Cl b. B, N, O, F c. O, S, F, Cl d. B, Si, N, P e. All eight elements can exceed the octet rule.
EXAM 3 WINTER 08-09 SHORT ANSWER 1. ANS: A MULTIPLE CHOICE 2. ANS: D PTS: 1 TOP: 6.8 Measuring Enthalpy Changes: Calorimetry 3. ANS: C PTS: 1 TOP: 6.9 Hess's Law 4. ANS: B PTS: 1 TOP: 6.9 Hess's Law 5. ANS: C PTS: 1 TOP: 6.10 Standard Molar Enthalpies of Formation 6. ANS: D PTS: 1 TOP: 6.10 Standard Molar Enthalpies of Formation 7. ANS: D PTS: 1 TOP: 6.11 Chemicals Fuels for Home and Industry 8. ANS: E PTS: 1 TOP: 8.1 Covalent Bonding 9. ANS: B PTS: 1 TOP: 8.1 Covalent Bonding 10. ANS: C PTS: 1 TOP: 8.2 Single Covalent Bonds and Lewis Structures 11. ANS: A PTS: 1 TOP: 8.2 Single Covalent Bonds and Lewis Structures 12. ANS: C PTS: 1 TOP: 8.2 Single Covalent Bonds and Lewis Structures 13. ANS: C PTS: 1 TOP: 8.2 Single Covalent Bonds and Lewis Structures 14. ANS: D PTS: 1 TOP: 8.3 Single Covalent Bonds in Hydrocarbons 15. ANS: A PTS: 1 TOP: 8.4 Multiple Covalent Bonds 16. ANS: D PTS: 1 TOP: 8.4 Multiple Covalent Bonds 17. ANS: A PTS: 1 TOP: 8.5 Multiple Covalent Bonds in Hydrocarbons 18. ANS: D PTS: 1 TOP: 8.5 Multiple Covalent Bonds in Hydrocarbons 19. ANS: C PTS: 1 TOP: 8.6 Bond Properties: Bond Length and Bond Energy 20. ANS: D PTS: 1 TOP: 8.6 Bond Properties: Bond Length and Bond Energy 21. ANS: A PTS: 1 TOP: 8.7 Bond Properties: Bond Polarity and Electronegativity 22. ANS: C PTS: 1 TOP: 8.7 Bond Properties: Bond Polarity and Electronegativity 23. ANS: C PTS: 1 TOP: 8.8 Formal Charge 24. ANS: C PTS: 1 TOP: 8.9 Lewis Structure and Resonance 25. ANS: B PTS: 1 TOP: 8.10 Exceptions to the Octet Rule 26. ANS: B PTS: 1 TOP: 8.10 Exceptions to the Octet Rule