CHEM 116

Indicate whether each of the statements below is true or false. Match the words in the left column to the appropriate blanks in the sentences on the right. Make certain each sentence is complete before submitting your answer. ResetHelp FalseFalse: C B r 4 has weaker intermolecular forces than C C l 4 .: CBr4 has weaker intermolecular forces than CCl4. FalseFalse: C B r 4 has a higher vapor pressure at the same temperature than C C l 4 .: CBr4 has a higher vapor pressure at the same temperature than CCl4. TrueTrue: C B r 4 has a higher boiling point than C C l 4 .: CBr4 has a higher boiling point than CCl4. FalseFalse: C B r 4 is more volatile than C C l 4 .: CBr4 is more volatile than CCl4.

Stronger dispersion forces would occur between CBr4 molecules because it has a higher molecular weight than CCl4. Therefore, CCl4 would be more volatile, which results in a higher vapor pressure (when compared at the same temperature) and a lower boiling point than that of CBr4. Volatility describes the tendency for molecules to escape from the liquid phase and into the gas phase, vapor pressure increases with the amount of molecules in the gas phase, and boiling occurs when the vapor pressure matches the surrounding pressure.

Dipole-dipole forces

arise from molecular dipole moments.

London dispersion forces,

found in all substances, result from the motion of electrons. These work to attract both polar and non polar molecules to one another via instantaneous dipole moments.

What mass of this substance must evaporate to freeze 250 g of water initially at 16 ∘C? (The heat of fusion of water is 334 J/g; the specific heat of water is 4.18 J/(g⋅K).)

he refrigerant would need to remove 1.7×104 J of heat to cool 250 g of water to 0∘C (based on water's specific heat), then it would need to remove 8.4×104 J of heat to freeze that amount of water (based on water's heat of fusion). The mass of refrigerant needed to perform both processes is then calculated based on its heat of vaporization. Significant Figures Feedback: Your answer 340 g was either rounded differently or used a different number of significant figures than required for this part.

Hydrogen-bond forces

result from the attraction of a hydrogen atom bonded to a small highly electronegative atom (N, O, and F) and the unshared electron pairs of another electronegative atom Physical properties such as boiling point, melting point, vapor pressure, viscosity, and surface tension are all affected by the strength of the intermolecular forces within a substance.

Ion-dipole forces

result from the interaction of an ion and a molecular dipole.