3.6: Quiz 1B Key

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1. Please indicate true (T) or false (F) for the following statements based on lecture materials (2 pts each):
  __T__ LiCl contains an ionic bond.
  __F__ Based on the number of valence electrons, a carbon atom can have either three, four or five bonds.
  __F__ If a carbon atom is sp² hybridized, then the bond angles will be 180˚.
2. For each of the following condensed structures, indicate how many lone pairs each molecule has. (1 pt each, put your numerical answer in the box provided)

CH₃Cl	CH₃CH₂CH₃	HONH₂	CH₃CH₂OH
3	0	3	2

(3 pts each) Draw a Lewis structure for the following species (including any lone pairs):

a) H₂CO	b) [CH₃NH₃]⁺

1. (2 pts) Covalent bonds may be polar or nonpolar. What property of the atoms forming a given bond determines this?
  electronegativity
2. Give an example for each of the following bond types (2 pts each):
  (Note: your answer does not need to be a valid Lewis structure, you can just show two atoms in a bond.)

polar covalent bond

non-polar covalent bond

C-F

C-Cl

C-Br

C-O

F-H

O-H

N-H

C-C

F-F

Br-Br

H-H

Based on the lecture notes and textbook page 8, C-H is also ok.

1. (4 pts) Briefly explain why a carbon atom cannot have more than 4 bonds?
  Carbon has 4 valence electrons and 4 orbitals that can each accept an electron to make 4 bonds (2 e^- each). More than 4 bonds would violate the octet rule because all orbitals are full.
2. (4 pts) Draw a structure of a molecule that has an sp-hybridized carbon that is directly attached to an sp²-hybridized carbon and clearly label these two carbon atoms with the hybridization. (Note: Your molecule can have any atoms in addition to these two carbon atoms. There are several possible answers, but make sure that your answer is a valid structure showing any hydrogens or lone pairs for full credit.)

These are several options.

Multiple choice (2 pts each, put your letter answer in the box provided)
What is the approximate value of the Br-C-Br bond angles in carbon tetrabromide, CBr₄?
1. 109˚
2. 120˚
3. 180˚
4. 90˚