### All AP Chemistry Resources

## Example Questions

### Example Question #71 : Compounds And Molecules

How many yellow spheres and green spheres are there per unit cell shown?

**Possible Answers:**

8 yellow, 1 green

2 yellow, 1 green

4 yellow, 1 green

1 yellow, 1 green

None of the above

**Correct answer:**

1 yellow, 1 green

For a unit cell, the corners count as 1/8 of a sphere and atoms completely within the unit cell count as 1. This gives us 1 yellow and 1 green sphere in the unit cell shown above.

### Example Question #2 : Structure Of Ionic Solids

Based upon the above image, what type of packing is this?

**Possible Answers:**

Tetragonal close packing (tcp)

Simple cubic packing (scp)

Hexagonal close packing (hcp)

Cubic close packing (ccp)

Body centered packing (bcp)

**Correct answer:**

Cubic close packing (ccp)

The figure above represents ABCABC packing which is cubic close packing.

### Example Question #2 : Structure Of Ionic Solids

Based upon the above image, what type of packing is this?

**Possible Answers:**

Tetragonal close packing (tcp)

Body centered packing (bcp)

Hexagonal close packing (hcp)

Cubic close packing (ccp)

Simple cubic packing (scp)

**Correct answer:**

Hexagonal close packing (hcp)

The figure above represents ABABA packing which is hexagonal close packing.

### Example Question #621 : Ap Chemistry

Zinc Sulfide can be described as a cubic close packed arrangement of Zn with sulfur occupying one-half of the tetrahedral holes. Based upon that description and the figure above, what is the formula for zinc sulfide?

**Possible Answers:**

Zn3S

Zn12S4

ZnS2

Zn2S

ZnS

**Correct answer:**

ZnS

The figure above has 8 Zn atoms on the corners (counting as 1/8) and 6 Zn atoms on the faces (counting as ½). This gives 4 Zn atoms in the unit cell. The Sulfur atoms are completely within the unit cell and count as 1 each for a total of 4 S atoms. This gives the formula Zn_{4}S_{4} which reduces down to ZnS.

### Example Question #1 : Structure Of Ionic Solids

What are the names of the alloy types shown in the figure above:

**Possible Answers:**

A = Pure Meta; B = Substitutional; C = Interstitial

A = Interstitial; B = Pure metal; C = Substitutional

A = Pure Metal; B = Interstitial; C = Substitutional

A = Substitutional; B = Interstitial; C = Pure Metal

None of the above

**Correct answer:**

A = Pure Meta; B = Substitutional; C = Interstitial

An interstitial alloy has a smaller atom inserted into the unit cell, a substitutional alloy has another atom substitute for the main element, and a pure metal is only composed of a single atom type.

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