Use the phase diagram of Substance X below to find the boiling point of X when the pressure on the liquid is 2.8 atm. pressure (atm) solid °C 200 liquid 400 X gas temperature (K) Note: your answer must be within 25 °C of the exact answer to be graded correct. 600

In each of the following groups of substances, pick the one that has the given property. Justify your answer. a. highest boiling point: HBr, Kr, or Cl2 b. highest freezing point: H2O, NaCl, or HF c. lowest vapor pressure at 25C: Cl2, Br2, or I2 d. lowest freezing point: N2, CO, or CO2 e. lowest boiling point: CH4, CH3CH3, or CH3CH2CH3 f. highest boiling point: HF, HCl, or HBr g.

What types of solids are these substances? (a) The hydrocarbon decane, C10H22, has a melting point of 31 C and is a poor electrical conductor. (b) Solid MgCl2 has a melting point of 714 C and conducts electricity only when melted.

A tank of gas at 21C has a pressure of 1.0 atm. Using the data in the table, answer the following questions. Explain your answers. a If the tank contains carbon tetrafluoride, CF4, is the liquid state also present? b If the tank contains butane, C4H20, is the liquid state also present?

In an experiment, 20.00 L of dry nitrogen gas, N2, at 20.0C and 750.0 mmHg is slowly bubbled into water in a flask to determine its vapor pressure (see the figure on next page). The liquid water is weighed before and after the experiment, from which the experimenter determines that it loses 353.6 mg in mass. Answer the following questions. a How many moles of nitrogen were bubbled into the water? b The liquid water diminished by how many moles? What happened to the liquid? c How many moles of gas exit the flask during the experiment? What is the partial pressure of nitrogen gas exiting? The total gas pressure is 750.0 mmHg. d From these data, calculate the vapor pressure of water at 20C. Does this agree with what you expect?

Which of the following substances can be liquefied by applying pressure at 25C? For those that cannot, describe the conditions under which they can be liquefied. Substance Critical Temperature Critical Pressure Sulfur dioxide, SO2 158C 78 atm Acetylene, C2H2 36C 62 atm Methane. CH4 82C 46 atm Carbon monoxide, CO 140C 35 atm

What are intermolecular forces? How do they differ from intramolecular forces? What are dipole-dipole forces? How do typical dipole-dipole forces differ from hydrogen bonding interactions? In what ways are they similar? What are London dispersion forces? How do typical London dispersion forces differ from dipole-dipole forces? In what ways are they similar? Describe the relationship between molecular size and strength of London dispersion forces. Place the major types of intermolecular forces in order of increasing strength. Is there some overlap? That is, can the strongest London dispersion forces be greater than some dipole-dipole forces? Give an example of such an instance.

The halogens form a series of compounds with each other, which are called interhalogens. Examples are bromine chloride (BrCl), iodine bromide (IBr), bromine fluoride (BrF), and chlorine fluoride (ClF). Which compound is expected to have the highest boiling point at any given pressure? Explain.

What term is used to describe a substance that readily evaporates at room temperature because of a high vapor pressure?

Classify each of the following statements as true or false. a Intermolecular attractions are stronger in liquids than in gases. b Substances with weak intermolecular attractions generally have low vapor pressures. c Liquids with high molar heats of vaporization usually are more viscous than liquids with low molar heats of vaporization. d A substance with a relatively high surface tension usually has a very low boiling point. e All other things being equal, hydrogen bonds are weaker than induced dipole or dipole forces. f Induced dipole forces become very strong between large molecules. g Other things being equal, nonpolar molecules have stronger intermolecular attractions than polar molecules. h The essential feature of a dynamic equilibrium is that the rates of opposing changes are equal. i Equilibrium vapor pressure depends on the concentration of a vapor above its own liquid. j The heat of vaporization is equal to the heat of fusion, but with opposite sign. k The boiling point of a liquid is a fixed property of the liquid. l If you break shatter an amorphous solid, it will break in straight lines, but if you break a crystalline solid, it will break in curved lines. m Ionic crystals are seldom soluble in water. n Molecular crystals are nearly always soluble in water. o The numerical value of heat of vaporization is always larger than the numerical value of heat of condensation. p The units of heat of fusion are kJ/gC. q The temperature of water drops while it is freezing. r Specific heat is conerned with a change in temperature.