Exam 16: Liquids and Solids

Shown below is a phase diagram for sulfur (not drawn to scale). Sulfur can exist in solid modifications, rhombic and monoclinic, denoted by S_R and S_M, respectively. Which of the following statements is incorrect?

Alkali halides commonly have either the sodium chloride structure or the cesium chloride structure. The molar mass of CsCl is 2.88 times the molar mass of NaCl, and the edge length of the unit cell for NaCl is 1.37 times the edge length of the CsCl unit cell. Determine the ratio of the density of CsCl to the density of NaCl.

In cubic closest-packed solids, what percentage of space is occupied by the spheres?

Given the phase diagram shown below, which of the following statements is false?

A certain substance, X, has a triple-point temperature of 20°C at a pressure of 2.0 atm. Which one of the following statements cannot possibly be true?

Shown below is a phase diagram for compound X. How will the melting point of X change with increased pressure?

A liquid placed in a closed container will evaporate until equilibrium is reached. At equilibrium, which of the following statements is not true?

How many grams of ice would be melted by the energy obtained as 18.0 g of steam is condensed at 100°C and cooled to 0°C?

The resistance of a liquid to an increase in its surface area is called

A metal crystallizes in a body-centered unit cell with an edge length of 2.05 × 10² pm. Assume the atoms in the cell touch along the cube diagonal. What will be the percentage of empty volume in the unit cell?

Chromium metal crystallizes as a body-centered cubic lattice. If the atomic radius of Cr is 1.25 angstroms, what is the density of Cr metal in grams per cubic centimeter?

Identify the major attractive force in Cl₂.

Mn crystallizes in the same cubic unit cell as Cu. Assuming that the radius of Mn is 5.6% larger than the radius of Cu and that the density of copper is 8.96 g/cm³, calculate the density of Mn.

Given below are the temperatures at which two different liquid compounds with the same empirical formula have a vapor pressure of 400 torr. Which of the following statements is false?

The unit cell in this two-dimensional crystal contains __________ Xs and __________ Os.

Based on the phase diagram shown below, which of the following statements are correct? I. Sublimation occurs at a point in the transformation that falls along a straight line from point A to point F. II. C and E represent points where the gas and liquid phases are in equilibrium. III. ΔH_vap can be measured at point B. IV. Molecules at point D have a greater average kinetic energy than those at point F. V. The temperature at point E is called the critical temperature of the compound.

Which of the following statements is true about the vapor pressures of methane (CH₄) and ammonia (NH₃)?

Molecular complexity leads to lower viscosity.

The triple point of iodine is at 90 torr and 115°C. This means that liquid I₂

MnO has either a structure like NaCl or a structure like CsCl. The edge length of the MnO unit cell is 4.47 × 10^-8 cm, and the density of MnO is 5.28 g/cm³. A. Does MnO crystallize like NaCl or like CsCl? B. If the ionic radius of oxygen is 140. pm, estimate the ionic radius of manganese. C. Does the calculated ratio of the cation radius to the anion radius for MnO support your answer in part A? Explain.