Ans_Ex1 - Nielsen CHM1041 Answer to Exercise Set 1 Liquids...

Info iconThis preview shows pages 1–3. Sign up to view the full content.

View Full Document Right Arrow Icon
Nielsen 1 CHM1041 Answer to Exercise Set 1 Liquids and Solids 1. a) Extent of intermolecular attractions: Gas < Liquid < Solid. In the gas phase the average intermolecular distance is beyond the range of significant intermolecular attraction. In the liquid phase the mobile molecules are in continuous contact, but they are less efficiently organized compared to the rigid geometry of the crystal lattice of the solid phase. b) Increasing molecular disorder: Solid < Liquid < Gas. The greater the freedom of motion at a given temperature, the greater is the disorder, or randomness, or entropy of the system. Independent gas molecules clearly have greater freedom than associated liquid molecules. Liquid molecules are still mobile and more random than the rigid placement of molecules within the solid crystal. c) At high pressures molecules are close to one another and at low temperatures they have less kinetic energy to resist intermolecular attractive forces. Liquid State 2. a) Strong intermolecular attractions will retard vaporization. The greater the attractions, the greater the energy required to free the molecules into the gaseous state. At any given temperature, only a fraction of the molecules has this kinetic energy, and this fraction of high energy molecules will decrease as the intermolecular forces increase. b) The boiling point is the temperature at which the vapor pressure of a liquid equals the external pressure. As stated above, the fraction of high energy molecules that may escape decreases as the intermolecular forces increase. If intermolecular forces increase, the boiling temperature would have to increase. Raising the temperature would be required to increase the fraction of high energy molecules that would again establish a vapor pressure equal to the external pressure. c) Recall that the enthalpy heat of vaporization, H vap , is the heat energy required to vaporize one mole of liquid at constant temperature. The greater the intermolecular attractions, the greater the energy required to free the molecules to the gaseous state. 3. The area under the curve at the high end of the Maxwell-Boltzmann distribution represents the fraction of molecules with the energy necessary to overcome the intermolecular attractions and escape to the vapor state. The average energy of the system is near the middle of the curve where the larger fractions are located. If the high energy molecules vaporize (are removed), the average kinetic energy of the remaining molecules will decrease and the temperature of the liquid will decrease.
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Nielsen 2 4. The entropy of vaporization is greater than the entropy of fusion because the change in the degrees of freedom of molecules going from the liquid phase to the highly random gas phase is significantly larger than the increase in disorder that occurs when solid particles become mobile liquid particles (molecular contact is maintained).
Background image of page 2
Image of page 3
This is the end of the preview. Sign up to access the rest of the document.

Page1 / 10

Ans_Ex1 - Nielsen CHM1041 Answer to Exercise Set 1 Liquids...

This preview shows document pages 1 - 3. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online