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Chemistry and Our Universe > Chapters 25-30 > Flashcards

Chapters 25-30 Flashcards

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1
Q

What is a crystal lattice?

A

A repeating geometric arrangement of atoms or molecules in space.

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2
Q

What is a unit cell?

A

The simplest repeating arrangement of atoms that can describe a crystal lattice unambiguously.

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3
Q

Approximately how much of the periodic table is metals?

A

3/4s

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4
Q

In 2-dimensional unit cells, what variables are of necessary?

A

2 sides, a and b. And the angle between them, alpha.

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5
Q

What are the a, b and alpha values in a square 2-D unit cell?

A

a = b, alpha = 90 degs.

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6
Q

What are the a, b and alpha values in a hexagonal 2-D unit cell?

A

a = b, alpha = 120 degs.

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7
Q

What are the a, b and alpha values in a rectangular 2-D unit cell?

A

a not = b, alpha = 90 degs.

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8
Q

What are the a, b and alpha value in an oblique 2-D unit cell?

A

a not = b, alpha not = to 90 or to 120 degs.

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9
Q

What are the a, b and alpha values in a centered rectangular 2-D unit cell?

A

a not = b, alpha = 120 degs.

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10
Q

How many 3-D unit cells are possible? What are they called?

A
  1. Bravais lattices.
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11
Q

When were Bravais lattices identified?

A

1848.

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12
Q

How many of the 14 Bravais lattices are cubic?

A
  1. primitive, body-centered, and face centered.
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13
Q

How efficiently is the space filled in a primitive cubic unit cell?

A

52%

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14
Q

What is the only metal with a primitive cubic lattice strucuture?

A

Polonium

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15
Q

How many nearest neighbors do the atoms in a primitive cubic lattice have?

A

6.

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16
Q

How efficiently is the space filled in a body-centered cubic lattice?

A

68%

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17
Q

How many nearest neighbors do the atoms in a body-centered cubic lattice have?

A

8

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18
Q

How efficiently is the space filled in a face-centered cubic lattice?

A

74%.

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19
Q

What two types of alloys are t here?

A

solid solutions and intermetallic compounds.

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20
Q

What is a solid solution?

A

2 molten metals are mixed in just about any composition. The metal atoms may bethoroughly mixed overall, but their arrangement within the product are not highly ordered.

21
Q

What is an intermetallic compound?

A

a very specific ratio of metal atoms is combined into a new, highly ordered, and sometimes very complex lattice.

22
Q

What are ionic solids?

A

Solids such as NaCl which form regular lattices in which atoms give up and receive electrons.

23
Q

What are molecular solids?

A

Ones in which the atoms of individual molecules are strongly bonded covalentlly, but the molecules are held to each other by weaker inter molecular forces.

24
Q

What is a network covalent material?

A

One in which covalent bonding chains reach across huge networks of atoms, bonding the entire solid together with great strength.

25
Q

What is glass?

A

Amorphous silicon dioxide (SiO2)

26
Q

What is quartz?

A

Crystalline silicon dioxide (SiO2).

27
Q

What is a solution?

A

Any homogeneous, or uniform, mixture of 2 or more substances.

28
Q

What is a solvent?

A

The more abundant phase into which other materials are dispersed.

29
Q

What is a solute?

A

The material dissolved in a solvent.

30
Q

What is molarity?

A

The moles of solute in a solution divided by the total volume of that solution in liters. M = n/V.

31
Q

What is molality?

A

The number of moles of solute divided, not by liters, but by Kilograms of the solvent in which it is dissolved.

32
Q

What is the mole fraction?

A

relative number of moles of the solute divided by the total number of moles in a solution.

33
Q

What are Svante Arrhenius’s dates?

A

1859-1927.

34
Q

What are electrolytes?

A

Ions dissolved in solution.

35
Q

What’s the difference between sugar and salt as solutes?

A

The water overcomes intermolecular forces in sugar breaking apart in tact molecules. But the water breaks apart the crystalline structure of NaCl, so individual sodium and chlorine ions are dissolved.

36
Q

What are Willebrord Snell’s dates?

A

1580-1626.

37
Q

What is one way to determine solution concentrations?

A

A refractometer can determine the densities of solution as light passes through them.

38
Q

What does the notion of “like dissolves like” mean for water?

A

Water, being a very polar substance, can form better interactions with polar, hydrogen-bonding, or ionic solutions like sugar or salt.

39
Q

What is the saturation point?

A

The point at which a solvent can not dissolve any more of a given solute.

40
Q

What is the solubility of a solute?

A

The concentration at which a solution is saturated. For sodium chloride, e.g., it is 6 moles or about 350 grams per liter.

41
Q

What is Henry’s law?

A

The relationship between pressure and solubility, which is Sg = kPg, where the proportionality constant, k, is known as Henry’s law constant for a particular gas.

42
Q

What is supersaturation?

A

a metastable state in which the temperature or pressure conditions on a saturated solution have changed so that the concentration of solute is higher than the ordinary saturation level.

43
Q

What are colligative properties?

A

Properties that depend only on the number of dissolved particles of solute, not necessarily the identity of the solute.

44
Q

What is the Van’t Hoff factor?

A

The ratio of dissolved particles that we get per mole of actual solute that we dissolve. It can be estimated simply using the stoichiometry of dissociation.

45
Q

What kind of properties are freezing and boiling points?

A

Colligative. They depend on the number of particles of solute, but not their identity.

46
Q

What is the rule of thumb about freezing and boiling points and solutions?

A

More concentrated solutions “prefer” to remain liquid, depressing the freezing point and increasing the boiling point.

47
Q

Why are first order processes particularly useful for dating?

A

Because their half-lives are equivalent periods of time.

48
Q

What is the half-life of Uranium 238?

A

4.5 billion years

49
Q

What is the half-life of Carbon 14?

A

5740 years.

Chemistry and Our Universe (6 decks)

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