Question 1:

Neon and HF have approximately the same molecular masses.

(a) Explain why the boiling points of Neon and HF differ.
(b) Compare the change in the boiling points of Ne, Ar, Kr, and Xe with the change of the boiling points of HF, HCl, HBr, and HI, and explain the difference between the changes with increasing atomic or molecular mass.

Question 2: It is often recommended that you let your car engine run idle to warm up before driving, especially on cold winter days. While the benefit of prolonged idling is dubious, it is certainly true that a warm engine is more fuel efficient than a cold one. Explain the reason for this.

Question 3: At 25 °C, how high will water rise in a glass capillary tube with an inner diameter of 0.63 mm? Refer to Example 10.4 for the required information.

Example 10.4:
Capillary Rise
At 25 °C, how high will water rise in a glass capillary tube with an inner diameter of 0.25 mm? For water, T = 71.99 mN/m and ρ = 1.0 g/cm³.

Solution

The liquid will rise to a height h given by: h = (2Tcos θ)/rpg
The Newton is defined as a kg m/s2, and so the provided surface tension is equivalent to 0.07199 kg/s2. The provided density must be converted into units that will cancel appropriately: ρ = 1000 kg/m3. The diameter of the tube in meters is 0.00025 m, so the radius is 0.000125 m. For a glass tube immersed in water, the contact angle is θ = 0°, so cos θ = 1. Finally, acceleration due to gravity on the earth is g = 9.8 m/s2. Substituting these values into the equation, and cancelling units, we have: h = 2??0.07199 kg/s2?? = 0.12 m =

h = (2(0.07199 kg/s2))/((0.000125 m)(1000 kg/m3)(9.8 m/s2)) = 0.12 m = 12 cm

Question 4: What is the relationship between the intermolecular forces in a solid and its melting temperature?

Question 5: Determine the state of water at:
(a) 35 °C and 85 kPa
(b) -15 °C and 40 kPa
(c) -15 °C and 0.1 kPa
(d) 75 °C and 3 kPa
(e) 40 °C and 0.1 kPa
(f) 60 °C and 50 kPa

Question 6: Pressure cookers allow food to cook faster because the higher pressure inside the pressure cooker increases the boiling temperature of water. A particular pressure cooker has a safety valve that is set to vent steam if the pressure exceeds 3.4 atm. What is the approximate maximum temperature that can be reached inside this pressure cooker? Explain your reasoning.

Question 7: Dry ice, CO₂(s), does not melt at atmospheric pressure. It sublimes at a temperature of -78 °C. What is the lowest pressure at which CO₂(s) will melt to give CO₂(l)? At approximately what temperature will this occur?

Question 8: Identify the type of crystalline solid (metallic, network covalent, ionic, or molecular) formed by each of the following substances:
(a) SiO₂
(b) KCl
(c) Cu
(d) CO₂
(e) C (diamond)
(f) BaSO₄
(g) NH₃
(h) NH₄F
(i) C₂H₅OH