CHEM PRACTICE EXAM IV CLASS - SPRING 2017 ANSWER KEY

Transcription

1 CHEM PRACTICE EXAM IV CLASS - SPRING 2017 ANSWER KEY 1. When Group 1A (except for H) and Group 17 (7A) elements react with each other, they are most likely to form: A. Covalent or ionic bonds B. Ionic bonds only C. Metallic bonds only D. any of these 2. When Group 16 (6A) and 17 (7A) elements react with each other, they are most likely to form: A. Covalent bonds B. Ionic bonds C. Metallic bonds D. Any of these 3. When forming a chemical bond, which of the following statements is true? A. The potential energy of the bonded atoms is greater than the potential energy of the separate B. The potential energy of the bonded atoms is less than the potential energy of the separate C. The potential energy of the bonded atoms is equal to the potential energy of the separate D. The kinetic energy of the bonded atoms increases. 4. In an ionic bond, which of the following is true? A. Electrons are transferred B. Electrons are shared C. Electrons are pooled D. Electrons are both shared and pooled. 5. In a polar covalent bond, which of the following is true? A. Electrons are transferred B. Electrons are shared unequally C. Electrons are shared equally D. Electrons are both shared and transferred 6. In the CN - ion, the formal charges (FC) on the atoms are A. FCC = 0, FCN = -1 B. FCC -1, FCN = 0 C. FCC =0, FCN = 0 D. FCC +2, FCN = Which salts are ranked correctly in terms of greatest lattice energy? A. NaCl > MgCl2 B. KCl > NaCl C. MgCl2 > CaCl2 D. SrO > CaO 8. Which of the following is the most electronegative atom? A. N B. O C. S D. P 9. Which of the following has a polar covalent bond? A. Cl2 B. HCl C. CsCl D. CH4 1

2 10. The Lewis structure of SO3-2 has A. 9 sets of unpaired electrons, 2 single bonds, 1 double bond B. 10 sets of unpaired electrons, 3 single bonds C. 7 sets of unpaired electrons, 3 double bonds D. 6 sets of unpaired electrons, 3 double bonds 11. NaNO3 contains A. only covalent bonds B. only ionic bonds C. covalent and ionic bonds D. metallic and covalent bonds 12. For the following reaction: CO (g) + 2 H2 (g) CH3OH (g) DC O = 1080 kj/mol; DH-H = 436 kj/mol; DC-H = 415 kj/mol; DC-O = 350 kj/mol; DOH = 464 kj/mol The enthalpy of the reaction is estimated to be: A kj/mol B kj/mol C kj/mol D kj/mol 13. For the reaction in Problem 12, A. The energy needed to break the bonds is greater than the energy released when the bonds form B. The energy needed to break the bonds is less than the energy released when the bonds form C. The energy needed to break the bonds is the same as than the energy released when the bonds form D. The reaction is endothermic 14. Which statement about bond lengths/ bond strengths is incorrect? A. C-C > C = C > C C/the C C is the strongest B. Br-Br > Cl-Cl > F-F/the F-F bond is the strongest C. C-N > C=N > C N/the C-N bond is the strongest D. Br-Br > Cl-Cl > F-F/the Br-Br bond is the weakest 15. Which statement is incorrect? A. The molecule BF3 has an octet around all of the elements B. The molecule NO is a free radical C. The molecule SF6 has an expanded valence shell for one of its atoms D. all of the statements are incorrect 2

3 16. The potential energy curve for the interaction of two hydrogen atoms is shown below. Which statement is incorrect? A. The two hydrogens repel each other in region A B. The two hydrogens do attract each other between regions D and C C. The hydrogen bond length is at C D. The equilibrium distance between the two H atoms is at B 17. The electron geometry of SBr2 is A. linear B. trigonal planar C. tetrahedral D. trigonal bipyramidal 18. The molecular geometry of SBr2 is A. linear B. bent C. tetrahedral D. T-shaped 19. The electronic geometry of IBr4 - is A. trigonal planar B. tetrahedral C. triginal bipyramidal D. octahedral 20. The molecular geometry of IBr4 - is A. bent B. octahedral C. square pyramidal D. square planar 21. Which of the following molecules is nonpolar? A. PF3 B. CCl4 C. CHCl3 D. SCl2 22. What is the hybridization of the C in CCl4? A. sp B. sp 2 C. sp 3 D. sp 4 3

4 23. Which statement about bonds is correct? A. sigma bonds are stronger than pi bonds B. sigma bonds exist between two bonded nuclei C. pi bonds are parallel to each other and perpendicular to the internuclear axis D. all are true 24. Which of the following molecules has a zero net dipole moment? A. B. C. D. all have a net zero dipole 25. Acetonitrile CH3-CN has A.4 sigma bonds and 1 pi bond B. 5 sigma bonds and 2 pi bonds C. 3 sigma bonds and 2 pi bonds D. 4 pi bonds and 1 sigma bond 4

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