CEM 141 EXAM 3 QUESTIONS AND
ANSWERS WITH SOLUTIONS 2024
change of state from solid -> liquid -> gas ________ energy - ANSWER requires
energy needed to phase change from solid --> liquid --> gas comes from: - ANSWER the surroundings
when phases change from solid --> liquid --> gas, interactions are _______ between molecules - ANSWER
overcome
change of state from gas --> liquid --> solid ______ energy - ANSWER releases
what happens to the energy from a phase change from gas --> liquid --> solid? - ANSWER released to
surroundings
when phases change from gas --> liquid --> solid, interactions are _______ between molecules - ANSWER
formed
what happens when a substance melts? - ANSWER the interactions between the particles have to be
overcome -- so that they can remove relative to each other (that's what allows a liquid to flow)
melting and boiling points provide an estimate of: - ANSWER the strength of the attractive interactions
between particles
which is stronger?? covalent bond/LDF - ANSWER covalent bond
in a covalent bond, what is formed? - ANSWER a new molecule
what is a LDF caused by? - ANSWER fluctuating charge distribution
covalent bonds are the sharing of: - ANSWER valence electrons
,LDF's increase with.... - ANSWER the size of electron cloud
covalent bonds are caused by: - ANSWER attraction between electrons of one atom and the nucleus of
another
LDFs are present where??? - ANSWER between all molecular species
is it hard or easy to predict covalent bond strength? - ANSWER hard
when are covalent bonds present? - ANSWER when atomic orbitals interact constructively
covalent bonds are located: - ANSWER between molecules/networks
LDFs occur between: - ANSWER separate molecules
diamond has a high/low melting point??? - ANSWER high
graphite has a high/low melting point?? - ANSWER high
diamond is hard/soft? - ANSWER hard
graphite is hard/soft? - ANSWER soft
diamond's physical properties - ANSWER brittle, translucent
diamond does/does not conduct electricity?? - ANSWER does not
graphite's physical properties - ANSWER slippery, shiny, grey
, graphite does/does not conduct electricity? - ANSWER does
in diamond, each carbon forms how many bonds to how many carbons??? - ANSWER 4 bonds to 4
identical carbons
in diamond, the bonds between carbons arrange themselves towards: - ANSWER the corners of a 4-sided
figure (tetrahedron)
what is the C-C-C bond angle in diamond? - ANSWER 109°
what model of bonding is used to explain the bonding in carbon? - ANSWER Valence Bond Theory
Valence Bond Theory - ANSWER atomic orbitals overlap to form bonds
how are bonds often shown in the valence bond theory? - ANSWER as "sticks"
in the Molecular Orbital Theory, atomic orbitals combine to form: - ANSWER an equal # of molecular
orbitals
in MO Theory, each orbital can contain up to ____ electrons - ANSWER 2
in MO theory, electrons in bonding orbitals (stabilized/destabilized) the system?? - ANSWER stabilized
in MO theory, each bond is made up of how many electrons? - ANSWER 2 electrons
in MO theory, electrons are localized where? - ANSWER the bond
in the Valence Bond Theory, atomic orbitals _____ to form a bond - ANSWER overlap
ANSWERS WITH SOLUTIONS 2024
change of state from solid -> liquid -> gas ________ energy - ANSWER requires
energy needed to phase change from solid --> liquid --> gas comes from: - ANSWER the surroundings
when phases change from solid --> liquid --> gas, interactions are _______ between molecules - ANSWER
overcome
change of state from gas --> liquid --> solid ______ energy - ANSWER releases
what happens to the energy from a phase change from gas --> liquid --> solid? - ANSWER released to
surroundings
when phases change from gas --> liquid --> solid, interactions are _______ between molecules - ANSWER
formed
what happens when a substance melts? - ANSWER the interactions between the particles have to be
overcome -- so that they can remove relative to each other (that's what allows a liquid to flow)
melting and boiling points provide an estimate of: - ANSWER the strength of the attractive interactions
between particles
which is stronger?? covalent bond/LDF - ANSWER covalent bond
in a covalent bond, what is formed? - ANSWER a new molecule
what is a LDF caused by? - ANSWER fluctuating charge distribution
covalent bonds are the sharing of: - ANSWER valence electrons
,LDF's increase with.... - ANSWER the size of electron cloud
covalent bonds are caused by: - ANSWER attraction between electrons of one atom and the nucleus of
another
LDFs are present where??? - ANSWER between all molecular species
is it hard or easy to predict covalent bond strength? - ANSWER hard
when are covalent bonds present? - ANSWER when atomic orbitals interact constructively
covalent bonds are located: - ANSWER between molecules/networks
LDFs occur between: - ANSWER separate molecules
diamond has a high/low melting point??? - ANSWER high
graphite has a high/low melting point?? - ANSWER high
diamond is hard/soft? - ANSWER hard
graphite is hard/soft? - ANSWER soft
diamond's physical properties - ANSWER brittle, translucent
diamond does/does not conduct electricity?? - ANSWER does not
graphite's physical properties - ANSWER slippery, shiny, grey
, graphite does/does not conduct electricity? - ANSWER does
in diamond, each carbon forms how many bonds to how many carbons??? - ANSWER 4 bonds to 4
identical carbons
in diamond, the bonds between carbons arrange themselves towards: - ANSWER the corners of a 4-sided
figure (tetrahedron)
what is the C-C-C bond angle in diamond? - ANSWER 109°
what model of bonding is used to explain the bonding in carbon? - ANSWER Valence Bond Theory
Valence Bond Theory - ANSWER atomic orbitals overlap to form bonds
how are bonds often shown in the valence bond theory? - ANSWER as "sticks"
in the Molecular Orbital Theory, atomic orbitals combine to form: - ANSWER an equal # of molecular
orbitals
in MO Theory, each orbital can contain up to ____ electrons - ANSWER 2
in MO theory, electrons in bonding orbitals (stabilized/destabilized) the system?? - ANSWER stabilized
in MO theory, each bond is made up of how many electrons? - ANSWER 2 electrons
in MO theory, electrons are localized where? - ANSWER the bond
in the Valence Bond Theory, atomic orbitals _____ to form a bond - ANSWER overlap
