Worksheet: Physical Effects of Intermolecular Forces

In this worksheet, we will practice describing the effect of intermolecular forces on properties such as hardness, solubility, and melting and boiling points.

Q1:

In which of the following sequences are the compounds arranged in order of increasing boiling point?

  • A C H < C H < C H 4 3 8 2 6
  • B C H < C H < C H 3 8 2 6 4
  • C C H < C H < C H 3 8 4 2 6
  • D C H < C H < C H 4 2 6 3 8
  • E C H < C H < C H 2 6 4 3 8

Q2:

The boiling points of the hydrogen halides increases in the order H C l < H B r < H I < H F .

Which interactions are responsible for the difference between the boiling points of H C l and H F ?

  • ADipole-dipole attractions
  • BDispersion forces
  • CIonic bonds
  • DHydrogen bonds
  • EIon-dipole attractions

Which interactions are responsible for the difference between the boiling points of H C l and H B r ?

  • ADispersion forces
  • BIonic bonds
  • CDipole-dipole attractions
  • DHydrogen bonds
  • EIon-dipole attractions

Q3:

Vegetable oil is immiscible with water. Based on the intermolecular interactions, why is this?

  • AWater only dissolves ionic substances.
  • BMolecules of oil pack more efficiently with each other, as they are much larger in size than molecules of water.
  • CMixing of oil and water is entropically unfavorable, as water molecules must form highly ordered shells around dissolved oil molecules.
  • DThe water-oil interactions are weaker than the sum of the water-water and oil-oil interactions.
  • EThe formation of an oil layer at the surface of the liquid is favorable, as the surface energy of oil is lower than that of water.

Q4:

Which of the following molecules forms the strongest hydrogen bonds?

  • A H B r
  • B H C l
  • C H I
  • D H F
  • E H 2

Q5:

Two diatomic molecules interact via dispersion forces. In general, which of the following quantities could be increased to increase the strength of the dispersion forces?

  • ABond polarity
  • BMolecular charge
  • CTemperature
  • DAtomic size
  • EBond energy

Q6:

Which of the following noble gases has the highest boiling point?

  • A N e
  • B H e
  • C A r
  • D X e
  • E K r

Q7:

In which of the following sequences are the compounds arranged in order of increasing boiling point?

  • A H C l < S i H < H O 4 2
  • B S i H < H O < H C l 4 2
  • C H C l < H O < S i H 2 4
  • D S i H < H C l < H O 4 2
  • E H O < H C l < S i H 2 4

Q8:

Why does the viscosity of a liquid decrease with heating?

  • AThe vapor pressure of the liquid increases.
  • BThe conformations of molecules become more linear.
  • CIntramolecular bonds are weakened.
  • DIntermolecular bonds are weakened.
  • EIntramolecular bonds vibrate more rapidly.

Q9:

What happens to the surface tension and viscosity of water with increasing temperature?

  • AViscosity increases and surface tension decreases.
  • BViscosity and surface tension both increase.
  • CViscosity decreases and surface tension increases.
  • DViscosity and surface tension both decrease.
  • EViscosity and surface tension are both constant.

Q10:

The density of liquid diethyl ether at standard temperature and pressure is 0.713 g/cm3. The density of gaseous diethyl ether vapor under the same conditions is 0.003 g/cm3. Which interactions are mainly responsible for the difference between the densities of the two phases?

  • ADipole-dipole attractions
  • BHydrogen bonds
  • CIonic bonds
  • DDispersion forces
  • EIon-dipole attractions

Q11:

The density of liquid phosphine ( P H ) 3 at 9 0 C and a pressure of 1 bar is 0.746 g/cm3. The density of gaseous diethyl ether vapor under the same conditions is 0.002 g/cm3. Which interactions are mainly responsible for the difference between the densities of the two phases?

  • ADipole-dipole attractions
  • BDispersion forces
  • CIonic bonds
  • DHydrogen bonds
  • EIon-dipole attractions

Q12:

Why is the enthalpy of vaporization of ethane higher than that of methane?

  • AThe ethane molecule has a larger area to interact with neighboring molecules via hydrogen bonding.
  • BThe ethane molecule has a larger dipole moment so it interacts more strongly with neighboring molecules via dipole–dipole attractions.
  • CThe more elongated shape of the ethane molecule allows for more densely packed molecular arrangements.
  • DThe ethane molecule has a larger area to interact with neighboring molecules via dispersion forces.
  • EThe lower symmetry of the ethane molecule destabilizes molecular clusters removed from the liquid surface during vaporization.

Q13:

The boiling point of ethanoic acid is greater than that of 1-propanol. Which interactions are mainly responsible for this difference?

  • ADipole-dipole attractions
  • BDispersion forces
  • CIonic bonds
  • DHydrogen bonds
  • EIon-dipole attractions

Q14:

For which of the following pairs of compounds is the difference in melting point mostly due to differences in the strength of hydrogen bonding?

  • ALithium hydride and sodium hydride
  • B 𝑛 -Hexane and cyclohexane
  • CDichloromethane and chloroflorm
  • D 𝑛 -Butane and 1-butanol
  • E1-Chloropropane and 2-chloropropane

Q15:

How does increasing the strength of intermolecular forces typically affect the surface tension and vapor pressure of a liquid?

  • ASurface tension decreases and vapor pressure increases.
  • BBoth quantities increase.
  • CBoth quantities decrease.
  • DSurface tension increases and vapor pressure decreases.
  • EBoth quantities remain constant.

Q16:

In which of the following sequences are the compounds arranged in order of increasing boiling point?

  • A C l < B r < F 2 2 2
  • B B r < C l < F 2 2 2
  • C F < B r < C l 2 2 2
  • D F < C l < B r 2 2 2
  • E C l < F < B r 2 2 2

Q17:

In which of the following sequences are the compounds arranged in order of increasing boiling point?

  • A S i H < H S < P H 4 2 3
  • B H S < P H < S i H 2 3 4
  • C P H < S i H < H S 3 4 2
  • D S i H < P H < H S 4 3 2
  • E P H < H S < S i H 3 2 4

Q18:

Which of the following properties of a liquid solution is not a consequence of evaporation?

  • AThe liquid volume in an open container decreases over time.
  • BThe liquid has a detectable smell.
  • CDroplets form on the side of the container above the liquid surface.
  • DThe liquid rises in a capillary tube.
  • ESolute crystals form on the side of the container above the liquid surface.

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