Liquid Chromatography

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9.1 Orbitals and Theories of Chemical Bonding

1. Which one of the statements concerning valence bond (VB) and molecular orbital (MO) bond theories is correct? a) MO theory predicts that electrons are localized between pairs of atoms. b) In VB theory, bonding electrons are delocalized over the molecule. c) MO theory accurately describes bonding in O2 and NO, VB theory does not. d) VB theory can describe molecular bonding in excited states. e) MO theory is used to accurately predict the colors of compounds.

Answer: c

9.2 Valence Bond Theory

2. Which of the following statements is/are CORRECT? 1. The overlap between an s orbital and a p orbital is called a pi-bond. 2. The overlap of two s orbitals in H2 is
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a) tetrahedral b) trigonal-bipyramidal c) square-planar d) square-pyramidal e) see-saw

Answer: d

21. What is the molecular geometry around a central atom that is sp2 hybridized, has three sigma bonds, and one pi bond? a) trigonal-planar b) trigonal-pyramidal c) bent d) T-shaped e) tetrahedral

Answer: a

22. What is the molecular geometry around a central atom that is sp3d hybridized and has one lone pair of eletrons? a) trigonal bipyramidal b) trigonal-pyramidal c) see-saw d) tetrahedral e) square-planar

Answer: c

23. What is the hybridization of a central atom that has four sigma bonds and has no lone pairs of electrons? a) sp b) sp2 c) sp3 d) sp3d e) sp3d2

Answer: c

24. Upon heating, CaCO3 decomposes to CaO and CO2. What change in the hybridization of carbon occurs in this reaction? a) sp to sp2 b) sp2 to sp3 c) sp3 to sp d) sp2 to sp e) no change

Answer: d

25. One product of the combustion of ethane, C2H6, is carbon dioxide. What change in hybridization of the carbon occurs in this reaction? a) sp3 to sp2 b) sp3 to sp c) sp2 to sp3 d) sp2 to sp3d2 e) sp2 to sp

Answer: b

26. Nitric acid, HNO3, dissociates in water to form nitrate ions and hydronium ions. What change in hybridization of the nitrogen atom occurs in this dissociation? a) sp2 to sp3 b) sp2 to sp c) sp3 to sp d) sp to sp3
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