Gen. chem Final Exam

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1

When should the latent heat of fusion be used?

When a substance is changing from a solid (ice) to a liquid (water) or vice versa

2

When should the latent heat of vaporization be used?

When a substance is changing from a liquid (water) to a gas (steam) or vice versa.

3

A phase change from a solid to a gas is called__________.

Sublimation

4

A phase change from a gas to a solid is called__________.

deposition

5

A phase change from a gas to a liquid is called__________.

Condensation

6

Which is generally greater in value:

The latent heat of fusion or The latent heat of vaporization?

The latent heat of vaporization

7

Why is the latent heat of vaporization generally greater in value than the latent heat of fusion?

The rearrangement is more extensive

8

Define Critical temperature

Temperature at which the kinetic energy is greater than the attractive forces, and therefore gas cannot be made to liquefy no matter how high the the pressure. The density of the gas becomes indistinguishable from the density of the liquid.

9

Define Supercritical fluid

any substance at a temperature and pressure above its critical point, where distinct liquid and gas phases do not exist.

10

A certain metal bromide, MBr, crystallizes in a primitive cubic unit cell with bromide ions at the lattice points. If the metal ions occupy cubic holes, how many bromide ions surround each metal ion in th metal bromide?

8

11

T/F: According to the band theory as applied to metallic bonding, the valence electrons of representative metals are free to move within the solid leading to thermal conductivity.

True

12

T/F: According to the band theory as applied to metallic bonding, the electrical conductivity of metallic solids decreases with increasing temperature.

True

13

T/F: According to the band theory as applied to metallic bonding, the bonds between neighboring metal atoms can be described as localized electron pair bonds

False

14

T/F: Most atomic solids have low melting points.

False

15

T/F: The faces of a unit cell must all be at angles of 90° to each other.

False

16

Define coordination number

the number of nearest neighbors at the same distance to a given atom

17

formula for the edge length of a unit cell (d)

d=r√8

18

Areas of zero probability of finding an electron are called _________.

nodes/nodal surfaces

19

What is Hund's rule?

the lowest energy configuration for an atom is the one having the maximum number of unpaired electrons allowed by the Pauli principle in a particular set of degenerate orbitals

20

The Greeks proposed that matter consisted of four fundamental substances:

fire, earth, water, air

21

The scientist whose alpha-particle scattering experiment led him to conclude that the nucleus of an atom contains a dense center of positive charge is_________.

Ernest Rutherford

22

A quantitative observation_________.

contains a number and a unit

23

What does the law of multiple proportions state?

When two elements combine to form more than one compound, the mass of one element, which combines with a fixed mass of the other element, will always be ratios of whole numbers.

24

If the Thomson model of the atom had been correct, Rutherford would have observed:

Alpha particles going through the foil with little or no deflection.

25

Who measured the charge/mass ratio of the electron.

J.J. Thomson

26

What did J.J. Thomson do?

Measure the charge/mass ratio of the electron.

27

What did Rutherford's experiment with alpha particle scattering by gold foil establish?

protons are not evenly distributed throughout an atom.

28

What scientist discovered the law of conservation of mass and is also called the father of modern chemistry?

Antoine Lavoisier

29

T/F: The Rutherford experiment proved the Thomson "plum-pudding" model of the atom to be essentially correct.

False

30

What component of atoms was discovered by Rutherford?

nucleus

31

Who is credited with discovering the atomic nucleus?

Rutherford

32

Who was the first chemist to perform truly quantitative experiments?

Robert Boyle

33

A pure substance composed of two or more different elements is a(n) ________.

chemical compound

34

What does the Law of Definite Composition state?

A given chemical compound always contains its component elements in fixed ratio (by mass).

35

What chemist is credited for inventing a set of symbols for writing elements and a system for writing the formulas of compounds (and for discovering selenium, silicon, and thorium)?

Baron Jöns Jacob Berzelius

36

A pure substance composed of two or more different elements is a(n) ________.

chemical compound

37

How many of the following postulates of Dalton's atomic theory are still scientifically accepted?

I. All atoms of the same element are identical.

II. Compounds are combinations of different atoms.

III. A chemical reaction changes the way atoms are grouped together.

IV. Atoms are indestructible.

2

38

What states that at the same temperature and pressure, equal volumes of different gases contain an equal number of particles?

Avogadro's hypothesis

39

Rutherford bombarded gold foil with alpha (a) particles and found that a small percentage of the particles were deflected. Which of the following was not accounted for by the model he proposed for the structure of atoms?

the total mass of the atom

40

T/F: Cathode rays always move toward the cathode (negative electrode).

False

41

What is a cathode ray?

a beam of electrons emitted from the cathode of a high-vacuum tube.

42

T/F: The emission spectrum of hydrogen contains a continuum of colors.

False

43

Excited hydrogen atoms radiate energy in the___________.

infrared, visible and ultraviolet regions.

44

What is a reasonable criticism of the Bohr model of the atom?

It does not adequately predict the ionization energy of the valence electron(s) for elements other than hydrogen.

45

T/F: It takes less energy to add an electron to nitrogen than to carbon because nitrogenwill be closer to achieving a noble gas configuration.

False

46

T/F: It takes more energy to add an electron to fluorine than to oxygen because the radius of fluorine is smaller and more repulsion would occur in the p-orbitals.

False

47

T/F: It takes more energy to add an electron to nitrogen than to carbon because of the extra repulsions that would occur in the 2p orbitals.

True

48

T/F: Less energy is released in adding an electron to iodine than to chlorine because the radius of iodine is larger and the electron is added at a distance further from the nucleus.

True

49

What type of spectrum, if any, would be produced if the light radiated by a heated atomic gas were to be dispersed through a prism?

discrete lines of different colors

50

T/F: A 2p orbital is more penetrating than a 2s; i.e., it has a higher electron density near the nucleus and inside the charge cloud of a 1s orbital.

False

51

The 2s orbital in calcium is more stable (more negative energy) than the 2p orbital even though the 2p orbital has its maximum electron density closer to the nucleus. The reason for this higher stability is:

due to its greater penetration, the 2s orbital has more electron density close to the nucleus than the 2p orbital

52

What does the Aufbau principle state?

Electrons orbiting one or more atoms fill the lowest available energy levels before filling higher levels.

53

T/F: Because Li is the strongest reducing agent of the alkali metals, it reacts most quickly with water of the alkali metals.

False

54

T/F: Subshell energies are higher in multielectron atoms than the same subshell in the hydrogen atom.

False

55

In the modern periodic table, the order in which the elements are placed is based on____________.

atomic number

56

T/F: Atomic radius increases from top to bottom in a group and decreases from left to right across a period.

True

57

After an atom has lost an electron it becomes a/an ______ and has a _______ charge.

cation, positive

58

T/F: Larger bond order means greater bond strength.

True

59

The concept of __________ is required for certain molecules because the localized electron model assumes electrons are located between a given pair of atoms in a molecule.

resonance

60

T/F: When balancing a chemical equation, it is generally best to start with the least complicated molecules.

False

61

T/F: For petroleum all of its hydrocarbon chains contain the same number of carbon atoms.

False

62

A(n) ________ is a pure substance that is composed of only one type of atom.

element

63

When a strontium salt is ignited, it burns with a red flame. The frequency of the light given off by this flame is greater than.

infrared light

64

The __________ quantum number is related to the size and energy of the orbital.

principal (n)

65

T/F: A state function does not depend on the system's past or future.

True

66

Describe Boyle's Law

The pressure of an ideal gas is inversely proportional to its volume at constant temperature and number of moles.

P1V1=P2V2

67

Describe Charles's law

Temperature of an ideal gas is directly proportional to its volume at a constant pressure and number of moles.

V1/T1=V2/T2

68

Describe Gay-Lussac's law

Temperature of an ideal gas is directly proportional to its pressure at a constant volume and number of moles.

P1/T1=P2/T2

69

Graphene was first prepared by removing layers from _________.

graphite

70

T/F: Most metals occur as ionic solids.

False

71

When liquid bromine is cooled to form a solid, which of the following types of solid would it form?

molecular

72

T/F: For face-centered cubic cell, a metal atom is located at each of the eight lattice points, where it is shared equally between eight unit cells.

True

73

T/F: For face-centered cubic cell, one metal atom is located on each face of the unit cell, where it is shared equally between four unit cells.

False

74

T/F: For face-centered cubic cell, one metal atom is located at the center of the unit cell.

False

75

In ionic solids, ________ occupy the lattice points.

ions

76

What is the simplest formula of a solid containing A, B, and C atoms in a cubic lattice in which the A atoms occupy the corners, the B atoms the body-center position, and the C atoms the faces of the unit cell?

ABC3

77

Define Doping

Adding trace amounts of an element to a substance to modify its properties.

78

An n-type semiconductor____________.

is doped with a valence e- rich element; "negative"

79

A p-type semiconductor_____________.

is doped with a valence e- deficient element; "positive"

80

Ephoton=

=hv=(hc)/λ

81

λ=

=h/(mv)

82

Describe the photoelectric effect

electrons are emitted from the surface of the metal when light strikes it.

83

Who is credited with first measuring the charge of the electron?

Robert Millikan

84

1 nanometer=how many meters?

=1x10-9 meters

85

Describe Hess's Law.

Regardless of the multiple stages or steps of a reaction, the total enthalpy change for the reaction is the sum of all changes.=>enthalpy is a state function.