51) Identify the compound with the highest boiling point. A) CH4 B) NH3 C) HF D) H2S E) H2O 52) The boiling point of H2O is much higher than that of the analogous molecule H2S. This is mostly due to A) dispersion forces being much stronger in H2S than in H2O. B) dipole-dipole forces being much stronger in H2S than in H2O. C) hydrogen bonding being much stronger in H2S than in H2O. D) dipole-dipole forces being much stronger in H2O than in H2S. E) hydrogen bonding being much stronger in H2O than in H2S. 53) The normal boiling point of diethyl ether is 34.6°C. At a pressure of 1.3 atm, the boiling point A) > 34.6°C. B) <34.6 °C. C) 34.6°C. D) There is not information given to solve the problem. 54) What happens when the vapor pressure of a liquid is equal to the external pressure? A) An equilibrium exists between the liquid and the solid state. B) The liquid freezes. C) The intermolecular forces become stronger in the liquid. D) The liquid boils. E) Dispersion forces become weaker in the liquid. 55) In which of the following substances should hydrogen bonding contribute to the attractive interactions in the molecules? A) CF4 B) HI C) H2Se D) N(CH3)3 E) None of the above 56) Which of the following must be overcome during the boiling of acetonitrile, CH3CN? 1. dispersion forces 2. dipole-dipole forces 3. hydrogen bonds A) 1 only B) 2 only C) 1 and 2 D) 1 and 3 E) 1, 2, and 3 57) The set of conditions at which point a phase boundary no longer exists is know as the A) freezing point. B) critical point. C) melting point. D) boiling point. E) sublimation point. 58) Calculate the energy that is required to change 50.0 g ice at -30.0°C to a liquid at 73.0°C. The heat of fusion = 333 J/g, the heat of vaporization = 2256 J/g, and the specific heat capacities of ice = 2.06 J /gK and liquid water = 4.184 J /gK. A) 3.50 × 104 J B) 2.14 × 104 J C) 1.31 × 105 J D) 6.59 × 103 J E) 1.66 × 104 J 59) The resistance of a liquid to flow is known as A) surface tension. B) meniscus. C) viscosity. D) capillary action. E) intermolecular forces. 60) Propanol has a normal boiling point of 97.8°C. At 400 torr, it has a boiling point of 82.0°C. What is the heat of vaporization? A) 24.9 kJ/mol B) 38.7 kJ/mol C) 12.3 kJ/mol D) 52.7 kJ/mol E) 44.4 kJ/mol 61) The heat required to melt 1 mol of a solid is known as the A) melting point. B) heat of fusion. C) freezing point. D) heat of vaporization. E) critical point.