Test 5: Biogeochemical Cycles, Balancing and Stoichiometry

Question 1

What are the reactions of the carbon cycle?

Answer 1

• Photosynthesis
• Respiration
• Combustion

Question 2

What reduces the amount of carbon in the atmosphere?

Answer 2

• Dissolution of carbon in water

- Photosynthesis

Question 3

What adds to the amount of carbon in the atmosphere?

Answer 3

• Combustion
• Respiration
• Volcanic eruptions
• Forest fires
• Decomposition

Question 4

What is the greenhouse effect?

Answer 4

1) Heat from sun warms the Earth
2) Earth radiates heat
3) Greenhouse gases reflect heat back (keep Earth warm)

Question 5

What’s the positive to the greenhouse effect?

Answer 5

The temperature would be -28 degrees without it (it keeps the Earth warm).

Question 6

What’s the negative to the greenhouse effect?

Answer 6

If there’s too much it will contribute to climate change/global warming.

Question 7

What’s nitrogen fixation?

Answer 7

When bacteria convert N2 to NO2 or NO3.

Question 8

What’s ammonification?

Answer 8

When bacteria converts NO2 or NO3 to NH3 or NH4.

Question 9

What is nitrification?

Answer 9

When bacteria converts NH3 or NH4 to NO2 or NO3.

Question 10

What is denitrification?

Answer 10

When bacteria converts NO2 or NO3 to N2.

Question 11

What is the order of the steps in the nitrogen cycle?

Answer 11

1) Nitrogen fixation
2) Ammonification
3) Nitrification
4) Denitrification

Question 12

What is the phosphorous cycle?

Answer 12

• Phosphorous moves into water through erosion.
• Phosphorous is absorbed into animals.
• Through decomposition - organic (dead fish) to inorganic (phosphorous).
• Due to decomposition - phosphorous can promote algae growth.

Question 13

What is eutrophication?

Answer 13

It is the enrichment of a waterbody with nutrients (nitrogen, phosphorous), resulting in the excessive growth of photosynthetic organisms (algae) and depletion of dissolved oxygen via decomposition (decomposers need lots of O2).

Question 14

What are the steps of eutrophication?

Answer 14

1) Algae gets fed and grows.
2) Algae bloom blocks light - takes nutrients.
3) Plants/others due and sink.
4) Less oxygen in water, more organisms (fish) die.

Question 15

What is a better alternative to fertilizer used to replace nutrients in agriculture?

Answer 15

Compost - no excess nutrients.

Question 16

What are the 5 chemical reactions?

Answer 16

• Photosynthesis
• Respiration
• Combustion
• Oxidation
• Neutralization

Question 17

What’s photosynthesis?

Answer 17

6 CO2 + 6 H2O + Energy —-> C6H12O6 + 6 O2

Question 18

What’s respiration?

Answer 18

C6H12O6 + 6 O2 —-> 6 CO2 + 6 H2O + Energy

Question 19

What is combustion?

Answer 19

Element + Oxygen —-> Carbon Dioxide + Water

Question 20

What are the sources of combustion?

Answer 20

• Volcanic eruptions
• Forest fires
• Fossil fuels

Question 21

What’s oxidation?

Answer 21

Oxygen is a reactant.

Question 22

What’s neutralization?

Answer 22

Acid + Base —-> Salt + Water

Question 23

What is the law of conservation of mass?

Answer 23

What goes in, must come out.

Question 24

Balance: 2 Fe2O3 + 3C —-> 3 CO2 + 2 Fe

Answer 24

2 Fe2O3 + 3C —-> 3 CO2 + 4 Fe

Question 25

Balance: AlBr3 + K2SO4 —-> KBr + Al2(SO4)3

Answer 25

2 AlBr3 + 3 K2SO4 —-> 6 KBr + Al2(SO4)3

Question 26

Balance: CF4 + Br2 —-> CBr4 + F2

Answer 26

CF4 + 2 Br2 —-> CBr4 + 2 F2

Question 27

Balance: Na3PO4 + CaCl2 —-> NaCl + Ca3(PO4)2

Answer 27

2 Na3PO4 + 3 CaCl2 —-> 6 NaCl + Ca3(PO4)2

Question 28

Blance: Al + HCl —-> H2 + AlCl3

Answer 28

2 Al + 6 HCl —-> 3 H2 + 2 AlCl3

Question 29

What does stoichiometry do?

Answer 29

It calculates how much of each chemical we need to produce while respecting the law of conservation of matter.

Question 30

2 KClO3 —-> 2 KCl + 3 O2

How many moles of O2 can be produced by letting 12.00 moles of KClO3 react?

Answer 30

2 mol KClO3/12 mol KClO3 = 3 mol O2/x

x = 18 mol O2

Question 31

2 K + Cl2 —-> 2 KCl

How many grams of KCl is produced from 2.50 grams of K and excess Cl2?

Answer 31

78.20g K/2.50g K = 149.10g KCl/x

x = 4.77g KCl

Question 32

C3H8 + 5 O2 —-> 3 CO2 + 4 H2O

How many moles of CO2 will be produced from 25g C3H8?

Answer 32

44.11g C3H8/25.00g C3H8 = 132.03g CO2/x
x = 74.83g CO2

132.03g CO2/3 mols CO2 = 74.83g CO2/x
x = 1.7 mols CO2

Question 33

2 HCl + Mg(OH)2 —-> MgCl2 + 2 H2O

How many grams of MgCl2 will be produced if there’s 1 mol of HCl?

Answer 33

2 mol HCl/1 mol HCl = 1 mol MgCl2/x
x = 0.5 mol MgCl2

95.20g MgCl2/1 mol MgCl2 = x/0.5 mol MgCl2
x = 47.60g MgCl2

Question 34

4 NH3 + 5 O2 —–> 4 NO + 6 H2O

When 1.20 mole of ammonia reacts, what is the total number of moles of products formed?

Answer 34

4 mol NH3/a.20 mol NH3 = 10 total moles of products/x

x = 3