A student is given four solid samples labeled W, X, Y, and Z. All have a metallic luster. She is told that the solids could be gold, lead sulfide (PbS), quartz which is SiO2,  and iodine. The results of her investigations are: (a) W is a good electrical conductor; X, Y, and Z are poor electrical conductors. (b) When the solids are hit with a hammer, W flattens out, X shatters into many pieces, Y is smashed into a powder, and Z is not affected. (c) When the solids are heated with a Bunsen burner, Y melts with some sublimation, but X, W, and Z do not melt. (d) In treatment with 6 M HNO3, X dissolves; there is no effect on W, Y, or Z. On the basis of these test results, which samples are; Au, PbS, SiO2, and I2

The P=T phase diagram of iron(Fe) is shown below, where the - Fe and -Fe phases are in body-centered cubic(bcc) structure, while the - Fe is in Face-centered cubic(fcc) structure. (a) Draw schematic G-T diagrams of Fe at 1 and 10^-8 atm and the G-P diagram at 1500 C. (b) Please draw schematic H-T and S-T diagrams of Fe at 1 atm. (d) Please draw schematic G-T and G-P diagrams of Fe at the fcc-liquid-Vapor triple point. (e) Please estimate the enthalpy change and entropy change of one mole of Fe being heated from 30 to 1500 °°℃. (f) Please estimate the enthalpy changes of one mole of fe under the → phase transformation at 500 and 1200 °C. (e) Please calculate the heat of evaporation of Fe at the normal boiling temperature. (h) Please explain why the phase boundaries of,, and /liquid equilibria are much steeper than those with the vapor phase in the phase diagram. Note: Please make sure the slopes and curvatures are with physical meanings

(a) Magnesium (Mg) has a hexagonal close-packed (HCP) crystal structure with the lattice parameter of a = 0.321 nm and c= 0.521 nm and the atomic radius is 0.173 nm. (i) What is the number of atoms per unit cell in HCP structure? (ii) Determine the atomic packing factor of the Mg unit cell. (iii) Is Mg containing an ideal atomic packing factor? You may justify your answer by evaluating the HCP c/a ratio. Subsequently, will slip be harder in Mg compared to the ideal HCP structure? Justify your answer.

(a) The unit cells of three structural types of ionic solids are shown below (the anions appear light and the cations dark). The anions occupy the lattice positions. X (B) (A) (i) Name the common structural type for (A), (B) and (C). (Hint: a typical structural type is rutile (T1O₂).] (C) (ii) The structures (A), (B) and (C) can be considered as packing of anlons with the cations occupying specific types of hole. For each structure: state the unit cell that the packing of anions is based on. state which holes are occupied by the cations and what fraction of them are occupied. State the coordination numbers of the cations and anions for (A), (B) and (C).