Chem 171 Midterm 2 Review

Front 1

Blackbody

Back 1

An object that is 100% efficient in emitting and absorbing light.

Hint 1

Ex. The sun

Front 2

The 'peak' wavelength in micrometers at which the max emission of energy occurs by a radiation blackbody (increases or decreases) inversely w/ (increasing/decreasing ) temp.

Back 2

Decreases/increasing

Front 3

The peak wavelength of the sun is about ___ and lies in the ___ region of the spectrum

Back 3

50 micrometers/visible

Front 4

What is an albedo

Back 4

The fraction of sunlight reflected back into space

Hint 4

Earth's albedo is ~30%

Front 5

Name 3 highly reflective surfaces on Earth

Back 5

Ice, Snow, Sand, Clouds

Front 6

Between what wavelengths does the Earth emitt energy? And what part of the spectrum is this?

Back 6

5~60 micrometers. Thermal Infared

Front 7

The rate of release of energy as light by a blackbody increases in proportion to the ____ power of its temperature

Back 7

Fourth

Front 8

Some gases in the air absorb thermal infrared light and sometimes dissipates it as heat. This phenomenon is called the ____ and ____ the temp. of the atmosphere?

Back 8

Greenhouse effect/increases

Front 9

True or false: The greenhouse effect is necessary for stabilizing the Earth's temperature.

Back 9

True

Front 10

What three gasses in the atmosphere are incapable of absorbing Infared light? Why?

Back 10

N2, O2, Ar/ Diatomic and have a dipole moment of zero, same goes for Argon cause it's by itself

Front 11

What two gases are have produced the most greenhouse gases? And about how much do they contribute?

Back 11

Water Vapor (2/3)

CO2 (1/4)

Front 12

Why does very little of the IR emitted at or near Earth's surface escape into space?

Back 12

Light is absorbed by the air close to the ground, and then re-emitted. This process continues and with increased altitude the amount of light absorbed and reflected decreases.

Front 13

Because of greenhouse gases emission of only ___ W/m^2 of energy is emitted by the Earth. While the atmosphere and surface of the Earth absorb about ___ W/m^2 of energy

Back 13

235/342

Front 14

An increase in CO_2 concentration is predicted to cause a cooling of the stratosphere. Why?

Back 14

1. More outgoing thermal IR is absorbed at low altitudes (troposphere) and less will warm the strat.

2.At strat. temps CO2 emits more thermal IR to space and to the trop. than it aborbs. Most warming at this level is due to water vapor and ozone.

Front 15

The ocillatory motion of two bonded atoms X--Y can be called.

Back 15

bond-stretching

Front 16

What occurs during a bending vibration?

Back 16

Three atoms X--Y--Z have a bond angle [theta] that changes

Front 17

What must happen to a molecule in order for IR light to be absorbed?

Back 17

A dipole moment: A change in its positive nuclei and negative electron cloud.

Front 18

Name at least 3 molecules that cannot absorb IR light.

Back 18

C-H, O-H, H2, Cl2, O3, CCl4

Front 19

Name at least 3 molecules that CAN absorb IR light.

Back 19

C-F, CO2, N2O, H2O, CO, NO

Front 20

The CO2 molecules that are now present in air collectively absorb about __ of the outgoing thermal IR light having wavelengths in the __-__ micrometer region

Back 20

half/ 14-16

Front 21

What three substances qualify as fossil fuels?

Back 21

Chiefly coal, oil, and natural gas

Front 22

What two actions of humans are mainly responsible for the annual anthropogenic release of CO2? And how much do they contribute?

Back 22

Deforestation: 1/4

Combustion of Fossil fuels: 3/4

Front 23

What is a temporary sink of CO2?

Back 23

dissolving in surface seawater or becoming absorbed by a growing plant

Front 24

What is permanent sink for CO2?

Back 24

dissolution in the deep waters of the ocean and/or precipitation there as an insoluble calcium carbonate.

Front 25

Define CO2 fertilization

Back 25

The increase in growth rate of certain types of trees due to the increased concentration of CO2 in the air

Front 26

Water molecules, always abundant in air, absorb thermal IR light throughtheir H-O-H _____ vibration.

Back 26

bending

Front 27

What is the most important greenhouse gas in Earth's atmosphere? (ie. what produces more warming?)

Back 27

H2O

Front 28

What is a positive feedback?

Back 28

the operation of a phenomenon produces a result that itself further amplifies theresult

Front 29

What is a negative feedback?

Back 29

a system whose output reduces the subsequentlevel of output

Front 30

What is H_2O's positive feedback loop?

Back 30

1. Rise in air temperature b/c of greenhouse gases heats the ice and water at the surface causing evaporation.

2. This produces more greenhouse gases b/c of the H2O

And thus the cycle continues

Front 31

True of False: Water in the form of liquid droplets in clouds also absorbs thermal IR.

Back 31

TRUE

Front 32

What is Earth's atmospheric window?

Back 32

8-13 micrometers

Front 33

The fraction of light absorbed by a gas as it passes through the atmosphere is __related to its concentration.

Back 33

logarithmically

Front 34

Name the three most important greenhouse gases in order.

Back 34

H2O, CO2, CH4(Methane)

Front 35

At what wavelength does CH4 absorb IR

Back 35

7.7 micrometers

Front 36

What is the average lifetime of methane?

Back 36

Less than a decade

Front 37

What is the dominant sink for atmoshperic methane?

Back 37

its reaction with molecules of hydroxl, OH.

Front 38

What molecules cause the strat. to cool? What molecules cause it to warm up?

Back 38

Cool: CO2

Warm: O3 and H2O(g)

Front 39

Why is it that, per molecule, increasing the amount of methane in air causes a much larger warming effect than adding more CO2.

Back 39

Each CH4 is much more likely to absorb a thermal IR photon that passes it than a CO2 molecule.

Front 40

Name 2 places that methane is currently immobilized in on Earth.

Back 40

1. Permafrost

2. Bottom of the oceans on continental shelves

Front 41

What occurs during denitrification?

Back 41

Fully oxidized nitrogen in the form of the nitrate ion, NO3- is reduced mostly to N2.

Front 42

What happens during Nitrification?

Back 42

Reduced nitrogen in the form of ammonia(NH3) or ammonium(NH4+) is oxidized mostly to nitrate (NO2-) and nitrate ions.

Front 43

True or False: Sinks do exist for nitrous oxide N2O

Back 43

FALSE

Front 44

What are CFC's?

What are two examples?

Back 44

Chlorofluorocarbons

CFCl3 and CF2Cl2

Front 45

What can aerosols do to reduce global warming?

Back 45

They can reflect incoming sunlight, with the consequence that some of it is directed back into space and so is unavailable later for absorption at the surface

{Direct effect}

Front 46

What are the negative effects of purposely realeasing aerosols into the air?

Back 46

They can form clouds that can block the sun, thus reducing evaporation, but depleting living things of the nutrients and energy from the sun. {Indirect Effect}

Front 47

How do aerosols create a warming effect?

Back 47

Aerosols can absorb incoming and outgoing radiation [warming effect]

{Direct effect}