CHEM 141 exam 3 2025 Questions and
Answers
Why is nitrogen a gas at room temperature and carbon is a solid? - --CORRECT
ANSWER--the nitrogen molecules interact with each other through LDFs caused
by the momentary fluctuating dipoles. Carbon atoms form localized, strong
interactions between the atoms (covalent bonds). It would take much more energy
to break the bonds between the carbon atoms than it would to overcome the
LDFs between the nitrogen molecules
Using the evidence provided in the table, explain the pattern that you identified in
question 3. - --CORRECT ANSWER--The network solids have higher melting and
boiling points because both metallic bonds and covalent bonds are very strong
interactions. These strong interactions must be broken when the solid melts (or the
liquid boils). It would require a lot of energy (high temperature) to break these
interactions.
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, LDFs are relatively weak interactions. Less energy is required (lower temperatures)
to overcome these interactions. It is the LDFs (not the bonds within the
molecules) that are overcome when the solid melts.
What pattern do you see regarding the melting and boiling points of these elements
relative to the types of bonding and interactions overcome during a phase change?
- --CORRECT ANSWER--Elemental forms with very high melting and boiling
points are extended network solids. The atoms are held together by metallic
bonding or covalent bonds.
Elemental forms with lower melting and boiling points are made of either discrete
atoms or small molecules with LDFs between them.
Define ionization energy. - --CORRECT ANSWER--Ionization energy is the
energy to remove an electron from an atom or an ion.
Which atom has the larger ionization energy, calcium (Ca) or selenium (Se)? (This
is your claim.) - --CORRECT ANSWER--Se
What aspects of atomic structure control the electrostatic forces that determine the
ionization energy? (This is your evidence.) - --CORRECT ANSWER--effective
nuclear charge
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Answers
Why is nitrogen a gas at room temperature and carbon is a solid? - --CORRECT
ANSWER--the nitrogen molecules interact with each other through LDFs caused
by the momentary fluctuating dipoles. Carbon atoms form localized, strong
interactions between the atoms (covalent bonds). It would take much more energy
to break the bonds between the carbon atoms than it would to overcome the
LDFs between the nitrogen molecules
Using the evidence provided in the table, explain the pattern that you identified in
question 3. - --CORRECT ANSWER--The network solids have higher melting and
boiling points because both metallic bonds and covalent bonds are very strong
interactions. These strong interactions must be broken when the solid melts (or the
liquid boils). It would require a lot of energy (high temperature) to break these
interactions.
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, LDFs are relatively weak interactions. Less energy is required (lower temperatures)
to overcome these interactions. It is the LDFs (not the bonds within the
molecules) that are overcome when the solid melts.
What pattern do you see regarding the melting and boiling points of these elements
relative to the types of bonding and interactions overcome during a phase change?
- --CORRECT ANSWER--Elemental forms with very high melting and boiling
points are extended network solids. The atoms are held together by metallic
bonding or covalent bonds.
Elemental forms with lower melting and boiling points are made of either discrete
atoms or small molecules with LDFs between them.
Define ionization energy. - --CORRECT ANSWER--Ionization energy is the
energy to remove an electron from an atom or an ion.
Which atom has the larger ionization energy, calcium (Ca) or selenium (Se)? (This
is your claim.) - --CORRECT ANSWER--Se
What aspects of atomic structure control the electrostatic forces that determine the
ionization energy? (This is your evidence.) - --CORRECT ANSWER--effective
nuclear charge
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