chapter 8 basic concepts of chemical bonding
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Chapter 8 Basic Concepts of Chemical Bonding. Chemistry, The Central Science , 10th edition Theodore L. Brown; H. Eugene LeMay, Jr.; and Bruce E. Bursten. Troy Wood University of Buffalo Buffalo, NY 2006, Prentice Hall. - PowerPoint PPT PresentationTRANSCRIPT
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Chemistry, The Central Science, 10th edition
Theodore L. Brown; H. Eugene LeMay, Jr.;and Bruce E. Bursten
Chapter 8Basic Concepts of Chemical Bonding
Troy WoodUniversity of BuffaloBuffalo, NY 2006, Prentice Hall
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The electron configuration: 1s22s22p53s23p64s23d
7 is consistent with which atom?
1. Fe2. Co3. Cu4. Ni
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Correct Answer:
The electron configuration [Ar]4s23d
7 corresponds to cobalt.
1. Fe2. Co3. Cu4. Ni
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The electron configuration of Fe3+ is which of the following?
1. 1s22s22p53s23p64s23d6
2. 1s22s22p53s23p64s23d3
3. 1s22s22p53s23p63d5
4. 1s22s22p53s23p64s13d4
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Correct Answer:
1. 1s22s22p53s23p64s23d6
2. 1s22s22p53s23p64s23d3
3. 1s22s22p53s23p63d5
4. 1s22s22p53s23p64s13d4
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Arrange the following ionic compounds in order of increasing lattice energy: LiCl, NaCl, MgCl2
1. NaCl < LiCl < MgCl2
2. LiCl < NaCl < MgCl2
3. MgCl2 < NaCl < LiCl
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Correct Answer:
1. NaCl < LiCl < MgCl2
2. LiCl < NaCl < MgCl2
3. MgCl2 < NaCl < LiCl
Lattice energy depends on size of the ions and their charges. MgCl2 has the highest lattice energy because it has a more positive cation. LiCl is higher than NaCl because the interatomic distance between cation and ion is shorter.
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Which of the following carbon–carbon atom bonds would be expected to be the shortest?
1. CC
2. CC
3. CC
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1. CC
2. CC
3. CC
Correct Answer:
The bond length decreases as the bond enthalpy increases; in general, as the number of bonds between two atoms increases, the bond grows shorter and stronger.
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Based on the electronegativities of the atoms, which of the following bonds would you predict is most polar?
1. CC2. CN3. CO4. CSi5. CBr
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Correct Answer:
The difference in electronegativities is greatest between O (3.5) and C (2.5) for a net difference of 1.0. Each of the other combinations yields a smaller value for electronegativity difference.
1. CC2. CN3. CO4. CSi5. CBr
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Boron (B) has an electronegativity of 2.0; chlorine (Cl) has an electronegativity of 3.0. Which of the following BEST describes a BCl bond? 1. Ionic
2. Polar covalent
3. Nonpolar covalent
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1. Ionic
2. Polar covalent
3. Nonpolar covalent
Correct Answer:
The difference in electronegativities is 1.0 because Cl = 3.0 and B = 2.0. This is too low to be an ionic bond but too high to be a nonpolar covalent bond.
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Which of the following molecules has a zero dipole moment?
1. HF
2. H2O
3. CS2
4. CHCl3
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Correct Answer:
1. HF
2. H2O
3. CS2
4. CHCl3
Even though each C=S bond is polar, their dipole vector quantities cancel each other out, and CS2 has no net dipole.
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Which of the following BEST describes the formal charges on the atoms in the cyanide ion, CN ?
1. C = +1, N = 1
2. C = 1, N = +1
3. C = 0, N = 1
4. C = 1, N = 0
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Correct Answer:
The formal charges are calculated from the difference between number of valence electrons and number of electrons assigned to each atom in the Lewis structure, thus:
C: 4 valence e 5 e = 1N: 5 valence e 5 e = 0
1. C = +1, N = 1
2. C = 1, N = +1
3. C = 0, N = 1
4. C = 1, N = 0
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Which is predicted to have the longest carbon–oxygen bonds: CO, CO2, or CO3
2?
1. CO32
2. CO2
3. CO
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Correct Answer:
In CO, the carbon–oxygen bond is a triple bond, while in CO2 both carbon–oxygen bonds are double bonds. In CO3
2, there are three resonance structures and the average carbon–oxygen bond is 1 1/3.
1. CO32
2. CO2
3. CO
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1. 467 kJ2. +467 kJ3. +17 kJ4. 983 kJ
Calculate H from the following bond enthalpies for the reaction:
2 NCl3 N2 + 3 Cl2D(NCl) = 200, D(NN) = 941, D(ClCl) = 242 (all kJ/mol).
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Correct Answer:
H = (bond enthalpies of bonds broken) ( bond enthalpies of bonds formed)
H = 6(200) [941 + 3(242)]
H = 1200 (1667)
H = 467
1. 467 kJ2. +467 kJ3. +17 kJ4. 983 kJ