Intermolecular Forces Quiz
Questions: 16 · 10 minutes
1. Ethanol and dimethyl ether have the same molecular formula, C₂H₆O. At the same temperature, why does dimethyl ether generally have the higher vapor pressure?
Dimethyl ether is ionic, so it enters the vapor more easily
Dimethyl ether cannot hydrogen-bond with itself, so its overall attractions are weaker
Ethanol has a substantially larger molar mass
Ethanol has no permanent molecular dipole
2. Both ammonia and water can form hydrogen bonds, but water has the higher boiling point. Which explanation is best?
Ammonia has no lone pair available for intermolecular attraction
Water molecules are ionic, whereas ammonia molecules are covalent
Water forms especially strong, extensive hydrogen-bonding interactions through its O–H bonds and oxygen lone pairs
Only water experiences London dispersion forces
3. Methanol, CH₃OH, has a higher boiling point than methanethiol, CH₃SH, even though their molar masses are similar. What best explains this difference?
Methanol is ionic, while methanethiol is molecular
Methanol molecules form stronger hydrogen bonds with one another
Methanethiol has no intermolecular attractions
Methanol has more electrons and therefore stronger dispersion forces
4. In addition to London dispersion forces, which attraction occurs between HCl molecules?
Ion–ion attraction
Conventional hydrogen bonding
Ion–dipole attraction
Dipole–dipole attraction
5. Straight-chain pentane generally has a higher boiling point than its compact, highly branched isomer neopentane. What is the best explanation?
Neopentane forms stronger hydrogen bonds
Pentane has a larger molar mass
Pentane has more surface contact, allowing stronger overall dispersion attractions
Neopentane is nonpolar, while pentane is polar
6. Which type of attraction is present between all atoms and molecules?
London dispersion forces
Dipole–dipole attractions
Hydrogen bonding
Ion–dipole attractions
7. HF has a much higher boiling point than HCl. Which difference contributes most directly?
HCl is nonpolar and has no intermolecular attractions
HF is ionic in its pure liquid state
HF molecules form conventional hydrogen bonds
HF has more electrons and stronger dispersion forces
8. During boiling, a pure molecular liquid absorbs energy while its temperature remains constant. What is that energy primarily doing?
Breaking covalent bonds within each molecule
Increasing the molecular mass of the vapor
Converting nonpolar molecules into permanent ions
Overcoming intermolecular attractions so molecules can enter the gas phase
9. What is the principal intermolecular attraction between methane, CH₄, molecules?
Hydrogen bonding
London dispersion forces
Ion–dipole attraction
Dipole–dipole attraction
10. Which molecular feature allows conventional hydrogen bonding between molecules of a pure substance?
Hydrogen bonded to N, O, or F, with an available lone pair nearby
Hydrogen bonded to any nonmetal atom
A carbon–carbon double bond and a permanent dipole
At least one hydrogen atom and a symmetrical shape
11. Which pure substance cannot form conventional hydrogen bonds between its own molecules?
Water, H₂O
Ethanol, CH₃CH₂OH
Methylamine, CH₃NH₂
Dimethyl ether, CH₃OCH₃
12. When a sodium ion is surrounded by water molecules, what attraction occurs between Na⁺ and the partially negative oxygen ends of the water molecules?
Ion–dipole attraction
London dispersion force only
Ion–ion attraction
Dipole-induced dipole attraction
13. When acetone is mixed with water, what strong attraction can form between the carbonyl oxygen of acetone and a water molecule?
An ion–ion attraction
A covalent bond between the two oxygen atoms
A hydrogen bond in which the acetone oxygen acts as an acceptor
A hydrogen bond in which acetone donates an O–H hydrogen
14. Why are London dispersion forces generally stronger between I₂ molecules than between Br₂ molecules?
I₂ molecules form conventional hydrogen bonds
I₂ has a larger, more polarizable electron cloud
Iodine atoms carry permanent ionic charges
I₂ is polar, whereas Br₂ is nonpolar
15. Liquids A and B are compared at the same temperature. If A has stronger intermolecular attractions, which property is generally expected for A?
A higher vapor pressure
A lower boiling point
The same vapor pressure because the temperatures match
A lower vapor pressure
16. Each C=O bond in carbon dioxide is polar, yet CO₂ has no permanent molecular dipole. Why?
Its linear, symmetrical geometry makes the bond dipoles cancel
Dispersion forces remove the bond dipoles
The molecule rapidly changes between positive and negative charges
Carbon–oxygen bonds are actually nonpolar