AP Chemistry IMF Quiz & Test Review

What is the state of matter characterized by definite shape, definite volume, and fixed particle positions?

Solid.

What are the forces that exist within a molecule, holding atoms together?

Intramolecular bonding.

What are the forces that exist between particles (atoms, molecules, or ions)?

Intermolecular forces (IMF).

Which type of force is generally much weaker: ionic/covalent bonds or intermolecular forces?

Intermolecular forces.

What is the strongest type of intermolecular force listed?

Hydrogen Bond (inter).

What are the weakest attractive forces listed?

London Dispersion Forces (inter).

What is the mechanism that causes London Dispersion Forces?

Momentary electron imbalance leading to a temporary dipole.

What type of attraction exists between polar molecules that possess permanent dipole moments?

Dipole-dipole attraction.

What are the three highly electronegative atoms that, when bonded to hydrogen, result in hydrogen bonding?

Fluorine, Oxygen, or Nitrogen.

What is the force of attraction that exists between a fully charged ion and the partial charges on a polar molecule?

Ion-dipole force.

When an ionic compound dissolves, many ion-dipole attractions overcome which type of strong bond?

Ionic bonds (Coulombic forces).

What is the molecular property related to how easily an electron cloud can be distorted?

Polarizability.

What is the physical property defined as the resistance of a liquid to an increase in its surface area?

Surface tension.

What is the physical property defined as the resistance of a liquid to flow?

Viscosity.

What is the process by which a solid changes directly to a gas?

Sublimation.

What is the process by which a liquid changes to a gas?

Vaporization (evaporation).

What is the process by which a vapor changes to a liquid?

Condensation.

What is the temperature at which the vapor pressure of a liquid equals the external pressure?

Boiling point.

What is the temperature at which the solid and liquid phases have the same vapor pressure at 1 atm?

Normal melting point.

What is the energy required to vaporize 1 mole of a liquid at 1 atm pressure called?

Heat of vaporization (ΔHvap).

What is the pressure exerted by a vapor in equilibrium with its liquid or solid phase?

Vapor pressure.

What distinguishes a crystalline solid from an amorphous solid?

Crystalline solids have a regular, ordered arrangement of particles; amorphous solids do not.

What is the smallest repeating pattern of a crystalline solid called?

Unit cell.

What type of solid is held together by electrostatic attractions between positive and negative ions?

Ionic solid.

What type of solid is made up of atoms or molecules held together by weak IMFs?

Molecular solid.

What type of solid has atoms connected by extensive covalent bonds forming a network?

Covalent network solid.

What type of solid is made up of metal atoms held together by metallic bonds?

Metallic solid.

What are the constituent particles in an ionic solid?

Positive and negative ions.

What are the constituent particles in a metallic solid?

Positive metal cations and valence electrons.

What are the constituent particles in a molecular solid?

Molecules.

What are metallic solids like physically (other than shiny)?

Malleable and ductile.

What holds the sheets of graphite together?

Weak London dispersion forces.

What state of matter is incompressible and flows, with indefinite shape but definite volume?

Liquid.

What are gases assumed to have negligible volume and no attractive or repulsive forces between particles?

Ideal gases.

According to Coulomb's Law, the attractive force between two ions is directly proportional to what?

The product of the ionic charges (q₁q₂).

According to Coulomb's Law, it’s inversely proportional to what?

The square of the distance (r²) between ion centers.

Why are metals good electrical conductors?

Valence electrons are delocalized and free to move.

What type of alloy forms when atoms of comparable radius substitute for each other?

Substitutional alloy.

What type of alloy forms when smaller atoms fill the spaces between larger ones?

Interstitial alloy.

What type of solid is generally brittle, hard, and has a very high melting point?

Ionic solid.

What type of solid is generally soft, flexible, and has a low melting point?

Molecular solid.

What type of solid is often described as a single macroscopic molecule with continuous bonding?

Covalent network solid.

What are the two IMFs common to both polar and nonpolar molecules?

London dispersion and dipole-induced dipole forces.

What force mainly causes glucose to dissolve in water?

Hydrogen bonding or dipole-dipole interactions.

What bonding is present in a molecular solid like I₂(s)?

London dispersion forces.

Which two phases have particles in close contact with similar molar volume?

Solid and liquid.

What is the formula for total pressure of a gas mixture (ideal)?

Ptotal = PA + PB + PC + …

If IMF strength increases, what happens to boiling point and vapor pressure?

Boiling point increases, vapor pressure decreases.

Why does increasing the size of a nonpolar molecule raise its boiling point?

Larger molecules are more polarizable, increasing LDF strength.

If Compound A has lower vapor pressure than Compound B, which has stronger IMFs?

Compound A.

Why don’t ionic solids conduct in solid form but do when molten or dissolved?

Ions are fixed in solids but mobile in liquid or solution.

Why are ionic solids brittle?

Shifting layers cause like charges to align, creating repulsion and breaking the crystal.

Why does MgO have a higher melting point than NaCl?

Higher ionic charges → stronger Coulombic forces → more energy needed.

Why does LiF have higher lattice energy than NaF?

Li⁺ is smaller, so ions are closer and attraction is stronger.

Why does CH₄ have a lower boiling point than SiH₄?

SiH₄ has more electrons → stronger LDFs.

Why do H-bonding molecules have higher boiling points than those with only DDFs?

H-bonds are stronger due to high polarity and closeness of atoms.

What effect does adding an interstitial atom like C in Fe have?

Makes lattice rigid, decreases malleability and ductility.

Why are metals malleable and ductile?

Shifting layers don’t break metallic bonds due to mobile electrons.

Why does H₂O have a higher boiling point than H₂S?

H₂O has H-bonds; H₂S only has DDF and LDF.

Why is graphite soft?

Weak LDFs between layers let them slide easily.

Why does a compound with H-bonds have higher BP than one with only DDF/LDF?

Stronger total IMF strength.

Why does water form a concave meniscus?

Adhesive forces to glass are stronger than cohesive forces among water molecules.

Why can a larger nonpolar molecule have a higher BP than a smaller polar one?

Stronger LDFs from larger electron cloud.

Why is ice less dense than liquid water?

H-bonding creates an open lattice structure when frozen.

Which has higher BP: Br₂ or HCl?

Br₂, because its stronger LDFs dominate despite HCl’s polarity.

Why is glucose soluble in water but cyclohexane isn’t?

Glucose is polar; cyclohexane is nonpolar. Like dissolves like.

What forces are broken when water boils?

Intermolecular (H-bonds, DDF).

What forces are broken when water decomposes into H₂ and O₂?

Intramolecular (covalent bonds).

Why does HF(l) have higher ΔHvap than HBr(l)?

HF has strong H-bonding; HBr doesn’t.

Why is H–Br bond longer than H–F?

Br has more electron shells → greater atomic radius.

A crystalline substance melts low and doesn’t conduct — what solid is it?

Molecular solid.

Why does CS₂ have higher BP than COS?

Larger, more polarizable electron cloud → stronger LDFs.

Why is pentane a liquid and propane a gas at 298 K?

Pentane is larger → stronger LDFs → higher BP.

Why is methanol liquid but propane gas at 298 K?

Methanol has H-bonds; propane only LDFs.

Which has lower vapor pressure: C₅H₁₂ at 299 K or C₆H₁₄ at 275 K?

C₆H₁₄ — larger and cooler → lower vapor pressure.

Why does increasing temp raise vapor pressure?

Higher KE lets more particles escape to gas phase.

Why does CCl₄ behave more ideally than SiCl₄?

Smaller, weaker LDFs → less deviation from ideal.

A white solid melts at 320°C and conducts in solution — what is it?

Ionic solid.

Why is a Cu-Au alloy harder than pure gold?

Smaller Cu atoms disrupt lattice movement.

Why are ionic crystals brittle when layers shift?

Like charges align and repel.

If two compounds both have H-bonds but one has higher BP, why?

It has more H-bonding sites.

Compare viscosity at 25°C vs 75°C.

Lower at 75°C — more KE → weaker IMF hold.

Compare bond strength of Al₂S₃ and NaCl.

Al₂S₃ stronger — higher ionic charges.

If a liquid has a convex meniscus, what’s stronger: cohesion or adhesion?

Cohesion.

Which alcohol has higher BP: C₄H₉OH or C₂H₅OH?

C₄H₉OH — longer chain → stronger LDFs.

What forces are overcome when NaCl dissolves in water?

Ionic bonds and H-bonds/dipole forces in water.

When He condenses, what IMF acts?

LDFs only.

How do you find the partial pressure of a gas collected over water?

Pgas = Ptotal - PH₂O.

Why is C–O bond length in HCO₂⁻ intermediate?

Resonance averages single and double bond.

Why is I₂(s) a poor conductor?

Electrons are localized within molecules.

Why is PVC denser than PP?

Cl atom in PVC adds mass.

Why does vinyl chloride have a higher BP than propene?

Has Cl → dipole + LDFs → stronger IMFs.

What’s the weakest and strongest IMF pentane can experience?

Only LDFs.

Why is CCl₄ nonpolar despite polar bonds?

Symmetry cancels dipoles.

Which behaves more ideally: Kr or HCl gas?

Kr — nonpolar, weaker IMFs.

Why is glycerol’s viscosity so high?

Multiple H-bonding sites + tangled molecules.