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CEM 141 Final Exam pt 3 (Real Exam 3, Mock Exam 3, PP Lecture 26-35) (1)
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CEM 141 Final Exam pt 3 (Real Exam 3, Mock Exam 3, PP Lecture 26-35) (1)
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CEM 141 Final Exam pt 3 (Real Exam 3, MockExam 3, PP Lecture 26-35)
Yes because Graphite exists as 2D sheets of sp3 hybridized C atoms. Un hybridized p orbitals
can interact to form delocalized pi orbitals that extend throughout the sheet. Electrons in the pi
network can move freely - ANS-Can graphite conduct electricity? Why or why not?
True - ANS-T/F Pi bonds form from side to side overlap of atomic orbitals and free rotation is not
allowed around the bond
True - ANS-T/F Sigma bonds form from end to end overlap of atomic/hybrid orbitals and free
rotation is allowed around the bond
An extended network of boron and nitrogen atoms held together by covalent bonds -
ANS-Boron nitride is the second hardest substance known (after diamond) It has a very high
melting point, but does not conduct electricity. What types of bonding do you think are present in
boron?
high - ANS-diamond has a high/low melting point?
high - ANS-graphite has a high/low melting point??
hard - ANS-diamond is hard/soft?
soft - ANS-graphite is hard/soft?
brittle, translucent - ANS-diamond's physical properties
does not - ANS-diamond does/does not conduct electricity?
slippery, shiny, grey - ANS-graphite's physical properties
does - ANS-graphite does/does not conduct electricity?
4 bonds to 4 identical carbons - ANS-in diamond, each carbon forms how many bonds to how
many carbons?
the corners of a 4-sided figure (tetrahedron) - ANS-in diamond, the bonds between carbons
arrange themselves towards:
Formal charge= valence electrons-bonds-lone electrons - ANS-formal charge equation
, sp3 - ANS-The electron center geometry is tetrahedral what is the hybridization?
sp2 - ANS-The electron center geometry is trigonal planar what is the hybridization?
sp - ANS-The electron center geometry is linear what is the hybridization?
the bond angle (109.5) formed by an sp3 hybridized central atom - ANS-Tetrahedral bond angle
180 degrees - ANS-linear bond angle
120 degrees - ANS-trigonal planar bond angle
True - ANS-T/F when finding the molecular shape of a central atom you ignore the lone pairs
around that atom
2 because the London dispersion forces are stronger because the molecule is larger, so more
energy is required to overcome them - ANS-Which do you predict to have a higher boiling point
and why?
1. CH3OH
2.CH3CH2CH2OH
CR2H2 because it is a n unipolar molecule that can form stronger LDFs than CH4 - ANS-Would
you expect methane (CH4) or difluoromethane (CF2H2) to have the higher boiling point? why?
MgBr2 - ANS-What is the most likely formula for a compound formed between magnesium and
bromine?
NaF, because the ions are smaller making the attraction between them stronger so that more
energy is required to overcome these interactions - ANS-Which of the following compounds
would most likely have the higher melting point, NaF or CsBr? Why?
The electronegativity difference between the atoms because if the atoms have similar
electronegativities, valance electrons will be shared between nuclei and when the
electronegativities are very different the valence electrons will be completely transferred from
the less electronegative atom to the more electronegative atom - ANS-What can we use to
predict whether atoms interact through covalent binds or ion-ion interactions? and why?
KBr because charged ions are free to move relative to one another in the liquid state, but not in
the solid state - ANS-Which of the following substances conducts electricity in the liquid state,
but not the solid state?
1. KBr
2. Na
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