Deck 20: Molecular Spectroscopy and Photochemistry

Question 1

A heteronuclear diatomic molecule has m₁ < m₂. The center of gravity for the molecule is therefore closer to m₁.

Answer 1

False

Question 2

A diatomic molecule will always rotate about its

A) moment of inertia
B) center of gravity
C) all of the above
D) none of the above

Answer 2

B

Question 3

How many moments of inertia can a polyatomic molecule have?

A) 1
B) 2
C) 3
D) Up to 3N, where N is the number of atoms in the molecule

Answer 3

C

Question 4

Which of the following will affect the rotational constant, B:

A) Masses of atoms in the molecule
B) Bond lengths
C) Moment of inertia
D) All of the above
E) None of the above

Question 5

Which type of molecular spectroscopy is used to determine force constants in molecules?

A) Rotational
B) vibrational
C) electronic
D) a and b
E) all of the above

Question 6

Of the following types of radiation, which has the longest wavelength?

A) radio waves
B) microwaves
C) X-ray
D) visible
E) infrared

Question 7

Of the following types of radiation, which has the highest frequency?

A) radio waves
B) microwaves
C) X-ray
D) visible
E) infrared

Question 8

Of the following types of radiation, which has the highest energy?

A) radio waves
B) microwaves
C) X-ray
D) visible
E) infrared

Question 9

The zero point energy in vibrational spectroscopy is equal to

A) 2B
B) 1/2 hv
C) hv
D) hc
E) none of the above

Question 10

In the parabolic approximation used to solve the vibrational Schrödinger equation for diatomic molecules, the spacing between energy levels is equal to

A) 2B
B) 1/2 hv
C) hv
D) hc
E) none of the above

Question 11

At high vibrational levels, the spacing between the vibrational energy levels in the Morse potential

A) increases
B) decreases
C) asymptotically approaches zero
D) b and c
E) stays constant

Question 12

What is the reduced mass of the NO molecule

A) 16 u
B) 14 u
C) 7.5 u
D) 0.13 u

Question 13

Which type of radiation is used in vibrational spectroscopy?

A) radio waves
B) microwaves
C) X-ray
D) visible
E) infrared

Question 14

Molecules in excited electronic states can return to the ground electronic state by emitting a photon through the processes of fluorescence and phosphorescence. Which of these processes is faster?

A) fluorescence
B) phosphorescence
C) they occur at the same rate
D) more information is required to answer this question

Question 15

Lasers operate through the process of

A) fluorescence
B) spontaneous emission
C) stimulated emission
D) a and b
E) more information is required to answer this question

Question 16

Which of the following will have the maximum ultraviolet absorbance at the longest wavelength?

A)

B)

C)

D)

Question 17

Temperature increases with increasing altitude in the region of the atmosphere known as the

A) troposphere
B) stratosphere
C) mesosphere
D) all of the above
E) none of the above

Question 18

The destruction of ozone (O₃) typically takes place in the

A) troposphere
B) stratosphere
C) mesosphere
D) all of the above
E) none of the above

Question 19

Which of the following molecules significantly absorb infrared radiation and therefore contribute to the "greenhouse effect"?

A) N₂
B) CO₂
C) CH₄
D) a and b
E) b and c

Question 20

The Beer-Lambert law states that concentration is directly proportional to

A) absorbance.
B) transmittance.
C) molar absorptivity.
D) path length.
E) a and b

Question 21

The moment of inertia in a diatomic molecule is directly proportional to the

A) bond length
B) square of the bond length
C) square of the reduced mass of the molecule
D) a and c
E) b and c

Question 22

In a rigid diatomic molecule, the rotational lines are uniformly separated in frequency by a value of

A) B
B) 2hv
C) 2h/(8p²l)
D) 2B
E) a and c
F) c and d

Question 23

Bond force constants determine

A) bond strength
B) bond stiffness
C) molecular polarizability
D) moments of inertia
E) a and b

Question 24

The area under the peaks in an NMR spectrum are proportional to

A) The number of hydrogens atoms in a particular chemical environment
B) The number of hydrogen atoms in the molecule experiencing "spin flips"
C) The number of hydrogen atoms with electrons in excited electronic states
D) a and c
E) none of the above

Question 25

Which type of radiation is used in nuclear magnetic resonance spectroscopy?

A) radio waves
B) microwaves
C) X-ray
D) visible
E) infrared

Question 26

Spectroscopic experiments in the visible region of the spectrum involve excitation of

A) core electrons
B) valence electrons
C) nuclear spins
D) vibrational levels
E) none of the above

Question 27

Spectroscopic experiments in the X-Ray region of the spectrum involve excitation of

A) core electrons
B) valence electrons
C) nuclear spins
D) vibrational levels
E) none of the above

Question 28

Which of the following statements are true regarding chlorofluorocarbons (CFC's)?

A) They are unreactive in the troposphere.
B) They photodissociate to form chlorine atoms in the stratosphere.
C) They persist for a long time in the stratosphere.
D) All of the above
E) none of the above

Question 29

The lowest layer of the atmosphere is called the

A) thermosphere
B) stratosphere
C) troposphere
D) mesosphere

Question 30

The leaves of green plants appear green because they absorb this color of light.

A) green
B) violet
C) red
D) b and c
E) none of the above

Question 31

Absorption and emission are

A) single electron processes
B) two-electron processes
C) two-photon processes
D) processes that only allow for exactly one combination of angular momentum
E) all of the above

Question 32

Which molecule should have its proton NMR peak shifted most downfield relative to TMS?

A) CH₂I₂
B) CH₂Cl₂
C) CHCl₃
D) CH₂Br₂
E) Not enough information to answer the question

Question 33

Of the following, which is an extremely powerful oxidizer that participates in many tropospheric chemical processes?

A) carbon monoxide
B) hydroperoxyl radicals
C) hydroxyl radicals
D) peroxyacylnitrates
E) water