Q: A crystal is irradiated with X-rays of wavelength $\lambda = 154$ pm. The first-order reflection ($n=1$) is observed at an angle $\theta = 30.0^\circ$. What is the separation $d$ between the planes in the crystal?

$d = \frac{154}{2 \sin 30.0^\circ} = 154\,\text{pm}$

Question 1

Which equation is used to determine the distance between atomic planes in a crystal using X-ray diffraction?

Accepted Answer

$n\lambda = 2d\sin(	heta)$

Question 2

A crystal is irradiated with X-rays of wavelength $\lambda = 154$ pm. The first-order reflection ($n=1$) is observed at an angle $	heta = 30.0^\circ$. What is the separation $d$ between the planes in the crystal?

Accepted Answer

$d = \frac{154}{2 \sin 30.0^\circ} = 154\,	ext{pm}$

Question 3

Which of the following best describes a unit cell?

Accepted Answer

The smallest repeating unit that shows the pattern of arrangement for all the particles in a crystal lattice.

Question 4

How many atoms are present in a body-centered cubic (BCC) unit cell?

Accepted Answer

2

Question 5

A metal crystallizes in a face-centered cubic (FCC) structure with a unit cell volume $V = 64.0\,	ext{\AA}^3$. What is the edge length $a$ of the unit cell?

Accepted Answer

$a = 4.00\,	ext{\AA}$

Question 6

Which of the following solids is held together primarily by dispersion forces?

Accepted Answer

Solid xenon (Xe)

Question 7

Which of the following substances would you expect to have the highest melting point: Xe, Br$_2$, C$_5$H$_{12}$, CO, or CaO?

Accepted Answer

CaO

Question 8

Which of the following statements about metallic bonding is correct?

Accepted Answer

Metal atoms are held together by a sea of mobile electrons.

Question 9

What is the coordination number of a cation in the cesium chloride (CsCl) structure?

Accepted Answer

8

Question 10

Which of the following best explains why graphite is a good electrical conductor parallel to its sheets?

Accepted Answer

Delocalized electrons can move freely within the planes of carbon atoms.

Question 11

A simple cubic unit cell has an edge length $a = 300$ pm. What is the radius $r$ of the atom in this unit cell?

Accepted Answer

$r = 150$ pm

Question 12

Which of the following is a network covalent solid?

Accepted Answer

Diamond

Question 13

Which property is most characteristic of ionic solids?

Accepted Answer

High melting points due to strong coulombic forces

Question 14

Which of the following best describes the difference between hexagonal closest packing (hcp) and cubic closest packing (ccp)?

Accepted Answer

hcp has ABAB stacking, ccp has ABCABC stacking

Question 15

Which of the following statements about the packing efficiency of unit cells is correct?

Accepted Answer

Face-centered cubic unit cells have higher packing efficiency than body-centered cubic unit cells.

Question 16

Which of the following is a property of ceramics such as Al$_2$O$_3$ and MgO?

Accepted Answer

They are physically and chemically stable at high temperatures.

Question 17

Which of the following best describes a polymer?

Accepted Answer

A very large molecule made by repeated linking together of monomers.

Question 18

Which type of solid is most likely to be a good thermal and electrical conductor?

Accepted Answer

Metallic solid

Question 19

Which of the following statements about the band theory of solids is correct?

Accepted Answer

The valence band is the band of bonding molecular orbitals.

Question 20

Which of the following best describes the effect of doping a semiconductor with an electron-deficient impurity?

Accepted Answer

It creates a p-type semiconductor with electron holes in the valence band.

Chapter 13: Solids and Modern Materials – Study Notes

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