UNE CHEM 1011 - MIDTERM STUDY GUIDE
ACTUAL 2026 QUESTIONS AND VERIFIED
ANSWERS
SECTION 1: INTERMOLECULAR FORCES AND
PROPERTIES OF LIQUIDS
1. A hydrogen bond is characterized by:
A. The attraction of temporary dipoles produced by the
random asymmetries in electron motion
B. The electrostatic attraction between the permanent
dipoles in any polar molecule
C. The highly concentrated partial charge between an H atom
and F, O, or N atoms
D. The covalent sharing of electrons between two atoms in a
molecule
Answer: C
Rationale: A hydrogen bond is a special type of dipole-dipole
interaction that occurs when a hydrogen atom is bonded to a
highly electronegative atom (F, O, or N). The partial positive
charge on the hydrogen is highly concentrated, allowing it to
,interact strongly with lone pairs on electronegative atoms of
neighboring molecules. Option A describes London dispersion
forces, Option B describes general dipole-dipole forces, and
Option D describes covalent bonds .
2. Which of the following will have the strongest dipole-
dipole attractions?
A. NCl₃
B. CCl₄
C. BCl₃
D. Cl₂
Answer: A
Rationale: Dipole-dipole attractions occur in polar molecules.
NCl₃ is polar because nitrogen is more electronegative than
chlorine, and the molecule has a trigonal pyramidal shape
(asymmetrical) with a net dipole moment. CCl₄ is nonpolar due
to its symmetrical tetrahedral geometry, BCl₃ is nonpolar with
trigonal planar symmetry, and Cl₂ is nonpolar as a diatomic
molecule .
3. A cohesive force is:
,A. The result of the intermolecular forces that attract
identical molecules
B. The result of the intermolecular forces that attract
different molecules together
C. The result of covalent interactions between atoms in a
molecule
D. Always stronger than an adhesive force
Answer: A
Rationale: Cohesive forces are intermolecular attractions
between identical molecules. "Co-" means mutual or together,
so cohesive forces act between molecules of the same
substance. Adhesive forces (Option B) occur between
different molecules. The strength of cohesive versus adhesive
forces determines phenomena like meniscus formation .
4. ΔHᵥₐₚ is:
A. The energy change when a substance changes from the
liquid phase to the gas phase
B. The energy change when a substance changes from the
solid phase to the liquid phase
C. The energy change when a substance changes from the
liquid phase to the solid phase
, D. The energy change when a substance changes from the
solid phase directly to the gas phase
Answer: A
Rationale: ΔHᵥₐₚ (enthalpy of vaporization) is the energy
required to convert one mole of a substance from the liquid
phase to the gas phase. Vaporization is an endothermic
process (requires energy input). Option B describes ΔH_fus
(enthalpy of fusion/melting), Option C describes ΔH_freezing
(negative of fusion), and Option D describes ΔH_sub
(enthalpy of sublimation) .
5. A liquid in a tube will form a convex meniscus when:
A. The adhesive forces are stronger than the cohesive forces
B. The cohesive forces are stronger than the adhesive forces
C. The adhesive forces are equal to the cohesive forces
D. It's impossible to predict
Answer: B
Rationale: A convex meniscus forms when the cohesive forces
(attractions between identical molecules) are stronger than
the adhesive forces (attractions between the liquid and the
tube surface). This causes the liquid to minimize contact with
the tube wall, as seen with mercury in a glass tube. A concave
ACTUAL 2026 QUESTIONS AND VERIFIED
ANSWERS
SECTION 1: INTERMOLECULAR FORCES AND
PROPERTIES OF LIQUIDS
1. A hydrogen bond is characterized by:
A. The attraction of temporary dipoles produced by the
random asymmetries in electron motion
B. The electrostatic attraction between the permanent
dipoles in any polar molecule
C. The highly concentrated partial charge between an H atom
and F, O, or N atoms
D. The covalent sharing of electrons between two atoms in a
molecule
Answer: C
Rationale: A hydrogen bond is a special type of dipole-dipole
interaction that occurs when a hydrogen atom is bonded to a
highly electronegative atom (F, O, or N). The partial positive
charge on the hydrogen is highly concentrated, allowing it to
,interact strongly with lone pairs on electronegative atoms of
neighboring molecules. Option A describes London dispersion
forces, Option B describes general dipole-dipole forces, and
Option D describes covalent bonds .
2. Which of the following will have the strongest dipole-
dipole attractions?
A. NCl₃
B. CCl₄
C. BCl₃
D. Cl₂
Answer: A
Rationale: Dipole-dipole attractions occur in polar molecules.
NCl₃ is polar because nitrogen is more electronegative than
chlorine, and the molecule has a trigonal pyramidal shape
(asymmetrical) with a net dipole moment. CCl₄ is nonpolar due
to its symmetrical tetrahedral geometry, BCl₃ is nonpolar with
trigonal planar symmetry, and Cl₂ is nonpolar as a diatomic
molecule .
3. A cohesive force is:
,A. The result of the intermolecular forces that attract
identical molecules
B. The result of the intermolecular forces that attract
different molecules together
C. The result of covalent interactions between atoms in a
molecule
D. Always stronger than an adhesive force
Answer: A
Rationale: Cohesive forces are intermolecular attractions
between identical molecules. "Co-" means mutual or together,
so cohesive forces act between molecules of the same
substance. Adhesive forces (Option B) occur between
different molecules. The strength of cohesive versus adhesive
forces determines phenomena like meniscus formation .
4. ΔHᵥₐₚ is:
A. The energy change when a substance changes from the
liquid phase to the gas phase
B. The energy change when a substance changes from the
solid phase to the liquid phase
C. The energy change when a substance changes from the
liquid phase to the solid phase
, D. The energy change when a substance changes from the
solid phase directly to the gas phase
Answer: A
Rationale: ΔHᵥₐₚ (enthalpy of vaporization) is the energy
required to convert one mole of a substance from the liquid
phase to the gas phase. Vaporization is an endothermic
process (requires energy input). Option B describes ΔH_fus
(enthalpy of fusion/melting), Option C describes ΔH_freezing
(negative of fusion), and Option D describes ΔH_sub
(enthalpy of sublimation) .
5. A liquid in a tube will form a convex meniscus when:
A. The adhesive forces are stronger than the cohesive forces
B. The cohesive forces are stronger than the adhesive forces
C. The adhesive forces are equal to the cohesive forces
D. It's impossible to predict
Answer: B
Rationale: A convex meniscus forms when the cohesive forces
(attractions between identical molecules) are stronger than
the adhesive forces (attractions between the liquid and the
tube surface). This causes the liquid to minimize contact with
the tube wall, as seen with mercury in a glass tube. A concave
