Chemistry Of The Atmosphere

Question 1

What are the main gases in Earth’s atmosphere today?

Answer 1

80% nitrogen (N2), 20% oxygen (O2), small proportions of other gases

Includes carbon dioxide (0.03%), argon, and water vapor.

Question 2

What is the approximate age of Earth?

Answer 2

4.6 billion years

Question 3

What was the primary gas composition of Earth’s early atmosphere?

Answer 3

Mainly carbon dioxide (CO2), little to no oxygen (O2)

Similar to the current atmospheres of Venus and Mars.

Question 4

What role did volcanic activity play in the formation of the early atmosphere?

Answer 4

Released gases such as CO2 and H2O, contributing to the atmosphere and forming seas

Question 5

What gases were likely present in small proportions in the early atmosphere?

Answer 5

Methane (CH4) and ammonia (NH3)

Question 6

True or False: The proportions of gases in Earth’s atmosphere have remained constant for the last 200 million years.

Answer 6

True

Question 7

The Earth’s early atmosphere may have consisted mainly of _______.

Answer 7

carbon dioxide (CO2)

Question 8

What is the percentage of carbon dioxide in the atmosphere today?

Answer 8

0.03%

Question 9

What is the significance of the lack of evidence regarding Earth’s early atmosphere?

Answer 9

It creates uncertainty about its composition and characteristics

Question 10

What were the two main gases released by volcanic activity during Earth’s early history?

Answer 10

Carbon dioxide (CO2) and water vapor (H2O)

Question 11

What gas gradually built up in the atmosphere due to volcanic activity?

Answer 11

Nitrogen (N2)

Question 12

Fill in the blank: The early atmosphere of Earth may have resembled that of _______.

Answer 12

Venus and Mars

Question 13

What happened when oceans formed?

Answer 13

CO2 dissolved into the water.

Question 14

What is the chemical reaction for CO2 and water?

Answer 14

C02 + H20 → 2H + C03

Question 15

What did the precipitation of carbonates produce?

Answer 15

It produced sediments.

Question 16

What is an example of a carbonate?

Answer 16

CaC03 = Limestone

This reduced the amount of CO2 in the atmosphere.

Question 17

What are the five changes that occurred after the early atmosphere?

Answer 17

1. Oxygen increased (and supported life)
2. Carbon dioxide decreased
3. Methane decreased
4. Ammonia decreased
5. Nitrogen increased.

Question 18

How did oxygen increase in the atmosphere?

Answer 18

Algae and plants produced the O2 that is now in the atmosphere by photosynthesis.

Question 19

What is the photosynthesis equation?

Answer 19

carbon dioxide + water + Light → Glucose + oxygen

6CO2 + 6H20 + Light → C5H12O6 + 6O2.

Question 20

What happened over the next billion years regarding plants and oxygen?

Answer 20

Plants evolved and the percentage of O2 gradually increased to a level that enabled animals to evolve.

Question 21

How does photosynthesis decrease carbon dioxide?

Answer 21

Photosynthesis by plants and algae produces oxygen and uses up carbon dioxide from the atmosphere.

Question 22

How is carbon dioxide used in the formation of sedimentary rocks?

Answer 22

Carbon dioxide is used up in the formation of sedimentary rocks and fossils.

Question 23

How is limestone formed?

Answer 23

1) Carbon dioxide in the atmosphere dissolves in oceans to form carbonate ions (CO2 + H2O ↔ H+ + CO3).
2) Carbonate ions are used by marine organisms to build shells/skeletons out of calcium carbonate (CaCO3).
3) Upon death, the shells sink.
4) Shells/skeletons are buried/compressed over millions of years to form sedimentary rocks.

Question 24

What are fossil fuels?

Answer 24

Coal, crude oil, and natural gas are types of fossil fuels.

Question 25

How is coal formed?

Answer 25

1) Plants and trees use CO2 during photosynthesis to build their tissue.
2) Plants and trees die in swamps and decay in the absence of oxygen.

Question 26

How is crude oil and natural gas formed?

Answer 26

1) Crude oil and natural gas both formed from ancient biomass (plankton) buried in mud.
2) The remains of the plankton were covered by more sediment.
3) They were compressed over millions of years to form crude oil and natural gas.

Question 27

Why has the amount of CO2 in the atmosphere remained the same for the last 200 million years?

Answer 27

The amount of CO2 in the atmosphere has stayed the same because of the carbon cycle.

Question 28

How did methane decrease?

Answer 28

Methane reacted with the O2 that was being produced by photosynthesis.

Question 29

How did ammonia decrease?

Answer 29

Ammonia reacted with the O2 that was being produced by photosynthesis.

Question 30

How did nitrogen increase in the atmosphere?

Answer 30

Nitrogen gas (N2) is very unreactive, allowing it to build up in the atmosphere.