Atoms, Molecules, Extended Structures and Stoichiometry

158. (Solid solutions; Ch. 3 "Companion") The following trio of metals all form the BCC structure.

Which two metals are most likely to form a solid solution?

V and Mo, V and Na, Mo and Na

Additional example:

Which two elements are most likely to form a solid solution?

C and Si, C and Ge, Si and Ge

175. Hydrogen can occur as H (1 amu), 2H (deuterium, 2 amu), and 3H (tritium, 3 amu) with respective natural abundances of >99.98%, <0.02%, and almost 0, respectively. Do all water molecules have equal masses?

yes, no

Considering only these hydrogen isotopes, how many masses (integer amu) can occur?

3, 5, 9

176. Which member of the following pairs contains more atoms in the formula?

177. Locate the tetrahedral hole inside this unit cell that is defined, in part, by atoms number 4 and 5.

Which other numbered atoms define the tetrahedral hole?

1 and 3, 8 and 9, 13 and 14

At what value of z is its center?

0, 1/4, 1/2, 1

184. When the solid solution CdS0.5Se0.5 is reacted with excess strong acid, H+, the gases H2S and H2Se are released.

Which of the following plots represents the mass of each of the gases vs. mL of acid added, and which represents the volume of each of the gases vs. mL of acid added (i.e., label the y-axis)?

plot A represents the volumes of the two gases (H2S and H2Se) and plot B represents the masses of the two gases
plot A represents masses of the two gases and plot B represents volume of the two gases

Which of the two curves in plot B represents the mass of H2S?

1, 2

In which part of either plot is the acid the limiting reagent?

flat part
rising part

185. Which of the flasks below will contain a mixture when all the hydrogen reacts with oxygen to give water?

Flask A, Flask B

189. Buckyball (C60) crystallizes with the face-centered cubic structure. The layer sequence for a face-centered cubic unit cell is shown below. Each circle represents a buckyball molecule.

How many buckyball molecules are in the unit cell?

4, 6, 8

Potassium reacts with C60 to fill all the tetrahedral and octahedral holes of the FCC structure formed by the C60 molecules. What is x in the formula of the solid, KxC60? [The solid is a superconductor.]


218. Which of the parallelograms in the figure below are unit cells?

A, B, C

How many total heads are included in the correct unit cell?

4, 6, 8

(A digital camera can be used to quickly photograph students in an entire class at the beginning of a course; groups of several students can be photographed at a time, with subsequent computer cropping to produce individual pictures. The collection of class photographs can be distributed to everyone in the course with their preferred name to facilitate communication. These photographs can also be incorporated into a unit cell question, as shown above.)

237. Scanning tunneling microscopy depends upon the flow of electricity (current) between a surface and an atomically-sharp probe tip. Two plots of current vs. tip-to-surface distance are shown. Which is correct?




A, B

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