Chapter 12 Practice Test

Question 1

Water molecules are bent as shown in the diagram below. Suppose, however, that water molecules were linear. How would this change in structure most likely affect the polarity of the water molecule?

Answer 1

The water molecule would be nonpolar

Question 2

Which of the following molecules has the smallest dipole moment?

Answer 2

G

Question 3

What are the forces that cause molecules to attract other molecules called?

Answer 3

Intermolecular forces

Question 4

London (dispersion) forces are due to what?

Answer 4

temporary dipole moments

Question 5

Here is a list of substances and the type of force holding the substance together in the condensed state. What is the order of the substances from lowest boiling point to highest boiling point?

Answer 5

He, Cl2, PH3, NaCl

Question 6

The following table shows the name, formula, and phase at room temperature of three substances. All three are held together by London dispersion forces. What property accounts for the difference in the phase?

Answer 6

The electron clouds around bromine and iodine are larger and easier to distort, so it is easier to induce temporary dipole moments.

Question 7

The density of the steel of which a razor blade is composed is approximately seven times higher than water. Why does the razor blade float on the surface of water?

Answer 7

In maintaining the minimal surface area, the cohesion of the water molecules prevents the razor from dropping through the water.

Question 8

What makes fats and oils viscous?

Answer 8

The London forces experienced by the long nonpolar hydrocarbon chains

Question 9

The molecular weight (MW) of of water, methane and neon are very similar (see below), however, the boiling point of water is significantly higher than methane (CH4 ) and neon (Ne). What accounts for the relatively high boiling point of water?

Answer 9

The intermolecular interactions in water molecules are stronger than those in methane and neon and these causes the boiling point to be higher than would be expected from the molecular weight

Question 10

What do you need to add into a liquid system that has a higher intermolecular attraction to cause it to boil?

Answer 10

Energy

Question 11

What happens to vapor pressure when the surface area is increased?

Answer 11

Surface area has no effect on vapor pressure.

Question 12

When does boiling occur?

Answer 12

When vapor pressure is high enough to lift the atmosphere

Question 13

How can the Clausius-Clapeyron equation be used to determine the heat of vaporization of a substance? The equation is:

Answer 13

Plot a graph of ln (Pvap ) versus 1 / T and find the slope

Question 14

Iodine and frozen carbon dioxide pass directly from the solid phase to the gas phase. What is the phase change from solid to gas is called?

Answer 14

Sublimation

Question 15

The triple point for carbon dioxide is around 5.0 atmospheres, while the triple point for water is far below one atmosphere. What does this tell us about the behavior of water and carbon dioxide near atmospheric pressure?

Answer 15

Liquid CO2 cannot exist at one atmosphere so frozen carbon dioxide sublimates while ice melts

Question 16

There are three general categories of crystal. What characteristics distinguish the three categories?

Answer 16

Kind of particle: ion, atom, molecule

Question 17

In a covalent network solid, the lattice sites are occupied by atoms that have what?

Answer 17

Small differences in electronegativity

Question 18

There are seven primitive unit cells of crystal lattice structures. Which of the following is not one of the seven primitive unit cells?

Answer 18

Biclinic

Question 19

What is the difference between a crystal lattice and a unit cell?

Answer 19

A unit cell is the smallest portion of the crystal lattice that reveals the three-dimensional pattern of the lattice. A crystal lattice is the entire array.

Question 20

In a face centered cubic crystal lattice, each corner atom is shared between how many cells?

Answer 20

eight

Question 21

The length of the edge of a face-centered cubic cell of iridium is 383 pm. What is the radius of an atom of iridium?

Answer 21

135 pm

Question 22

What are the two different cells that can be produced by hexagonal close packing?

Answer 22

hexagonal and face-centered cubic

Question 23

In a body-centered cubic lattice, each atom has 8 nearest neighbors. How many nearest neighbors does an atom in a face-centered cubic lattice have?

Answer 23

12

Question 24

Which of the following is not a characteristic of ceramics?

Answer 24

They melt at low temperature

Question 25

The seven types of unit cell discussed are known as what?

Answer 25

Primitive unit cells