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Environmental Chemistry > Test One > Flashcards

Test One Flashcards

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1
Q

What are the purpose of nuclear reactions on the composition of the elements on Earth?

A

Nuclear reactions determine the relative abundance of the elements

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2
Q

What do you call the reactions that determine the oxidation states of the elements on the Earth surface?

A

Electronic reactions

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3
Q

What do metal ligand reactions determine

A

The determine where on Earth that the elements would be located/ found on the Earth’s surface

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4
Q

In a graph which shows the abundance of the elements as a function of their atomic number, why is there a noticeable zigzag like pattern?

A

The zigzag pattern of a relative abundance graph of the elements is due to the fact that even # atomic numbers are usually higher in abundance than odd numbered atomic numbers

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5
Q

true or false, the abundance of the first 50 elements decreases

A

true

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6
Q

what elements are anomalously low in relative abundance

A

Li, Be, B
Lithium
Beryllium
Boron

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7
Q

Which element is anomously high

A

Fe

Iron

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8
Q

Which elements have no stable isotopes, state their atomic number

A

Technitium (43), Tc

Promethium (61), Pm

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9
Q

True or false, elements bigger than Bismuth (83) have no stable isotopes

A

true

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10
Q

True or false, elements bigger than Bismuth (83) decay products from long lived isotopes of U (uranium) and Th (thorium)

A

true

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11
Q

True or false, all particularly nasty and toxic elements have a lower relative abundance in the universe

A

true

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12
Q

Give five examples of the nasty, toxic elements in the universe that are low in abundance

A 
Beryllium
Mercury Hg (80)
Arsenic As (33)
Lead Pb (82)
Cd Cadmium (48)
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13
Q

Atomic number of Hg

A

80

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14
Q

Atomic number of As

A

33

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15
Q

Atomic number of Pb

A

82

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16
Q

Atomic number Cd

A

48

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17
Q

Where do elements come from

A

Big Bang and Dead Stars

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18
Q

What is the big bang

A

Rapid expansion and cooling, formation of the universe

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19
Q

What happened between 0-1 uS in the big bang

A

formation of neutrons and protons

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20
Q

What happened between 0-20 mins of the big bang

A

D and He formed when the temperature was not too cold and not too hot

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21
Q

what happens in the big bang when its too hot

A

any deuterium formed will be destroyed

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22
Q

what happens when in the big bang it gets too cold

A

don’t get nuclear fusion

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23
Q

Why are elements heavier than helium not formed during the big bang

A

Not formed during the big bang because of the brief time and an energy gap after He; the Lithium energy barrier is really large (large energy gap between He and Li)

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24
Q

How were the other 90 elements formed

A

the other 90 elements were formed in stars but several processes are involved

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25
Q

How are stars formed

A

Stars are formed when a cloud of interstellar gas contracts under the influences of gravity

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26
Q

what happens when the pressure increases in the star’s core

A

the temperature increases

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27
Q

What happens when the temperature reaches 20*10^6K

A

hydrogen fusion can occur and a star is born

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28
Q

true or false, for 90% of the life of a star only hydrogen fusion occurs 4 H to He

A

true

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29
Q

what happens 90% of the life of a star

A

hydrogen fusion occurs

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30
Q

true or false, the nuclear reactions that can occur in a star are governed mainly by temperature

A

true

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31
Q

When can elements heavier than He be made

A

Although the energy that hydrogen fusion provides prevents the gravitational collapse of a star therefore when hydrogen gets depleted the core compresses and the temperature increases thus the conditions will become right for making elements heavier than He (dying star)

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32
Q

true or false, intermediate size stars can produce Fe

A

true

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33
Q

how did the solar system form

A

from contracting and spinning dust cloud

34
Q

what causes the separation of some elements

A

the gradient between temperature and pressure based on their boiling points; therefore planets closest to the sun are rocky (high bp) while beyond Mars they are gaseous ( low bp)

35
Q

Since its too cold for cold fusion reactions on Earth what determines the behavior of elements on earth

A

Electron energies

36
Q

true or false, stars are about nuclear reactions whilst planets are about electron energies

A

true

37
Q

which side of the periodic table are recipients of electrons

A

on the right hand side

38
Q

which part of the periodic table are elements the most abundant

A

the even MASS atoms and the first row elements

39
Q

On Earth, which element determines the oxidizing conditions of the planet

A

Oxygen (pO2)

40
Q

what is the standard reduction potential of O2 reduction

A

1.23 V

41
Q

what are standard conditions

A

1 M
1 atm
0 C (or specified temperature)

42
Q

true or false, the more positive E is the most easily that Metal is to reduce

A

true

43
Q

why do oxides float in comparison to metals

A

oxides are lighter

44
Q

What is the typical oxidation state of G1 elements on Earth (give example)

A

+1 (Na and K)

45
Q

what are the typical oxidation states of G2 earth metals and give examples

A

Mg and Ca

46
Q

G17 oxidation state (give example)

A

-1 (Cl, Br, etc halides)

47
Q

What is the typical oxidation state of oxygen

A

0 or -2

48
Q

ox state of Carbon (C) and give examples

A

-4 to +4 CH4, CO2

49
Q

ox state of Nitrogen (N) give examples

A

-3 to +5 NH3 to NO3-

50
Q

ox state of Al

A

+3

51
Q

ox state of Si

A

+4

52
Q

Ox state of Phosphorous (P)

A

+5 as PO4-3

53
Q

ox state of S give example

A

-2 to +6 sulfide to sulfate

54
Q

Ox state of As (Arsenic) give examples

A

+5 as AsO4 (-3) and +3 (H3AsO3)

55
Q

ox state of Cr

A

+3 or +6 (Cr+3 or CrO2 2-)

56
Q

ox state Mn

A

+2, +4,+7 (permanganate)

57
Q

ox state of Fe

A

+2 or +3 (ferrous or ferric)

58
Q

ox state of Cu

A

+1 and +2 (cuprous or cupric)

59
Q

Ox state of Zn

A

+2

60
Q

ox state of Cd

A

+2

61
Q

true or false, as you move down the sediment the amount of O2 decreases

A

true

62
Q

In estuarine soils why is the top layer brown

A

due to Fe being Fe3+ and S being SO4 2-; color due to Fe 3+ oxides

63
Q

What happens at the lower layers of estuarine soils

A

the bottom layer is black in color; due to fine grained iron sulfides

64
Q

why is the color of the bottom layer of estuarine soils black

A

Fe 3+ is reduced to Fe2+ and SO4 2- is reduced to S2-; the black is due to fine grained Iron Sulfides

65
Q

true or false, transition metal sulfides are typically very low in solubility

A

true

66
Q

true or false, the number of waters attached to a cation depends on the size of central cation

A

true

67
Q

true or false, the protons coordinated to the cation will be more acidic than the protons free

A

true

68
Q

true or false, if the coordinated water is deprotonated, the charge decreases (eg. Fe3+ to Fe2+)

A

true

69
Q

true or false, cation precipitation involves removing protons to form a neutral species

A

true

70
Q

what happens the solubility of cations at low pH and how much H+ ions are present at low pH

A

at low pH cations are more soluble

H+ conc is high

71
Q

what happens to the solubility of cations at high pH and how much H+ is present

A

at high pH cations are less soluble

low H+ present in soln

72
Q

how does cation ppt occur (ppt = precipitation)

A

protons from coordinated water ligands must be removed

73
Q

true or false, cations of high charge density (z/r) lose protons more easily (eg. at lower pH)

A

true

74
Q

what does it mean if a cation loses protons much easily

A

it means that ppt formation is more likely and these cations will thus be less soluble

75
Q

soluble or less soluble, low charge (z), large radius (r)

A

this means it will have a low charge density thus it will be more soluble

76
Q

Would precipitation occur for G1 cations and why

A

PPT will not occur, this is because Na+ and K+ have a large atomic radii and have a low charge; therefore the H2O coordinated to the cation are NOT acidic, and ppt is not seen

77
Q

what is the effect of precipitation on G2 cations

A

cations such as Mg 2+ and Ca 2+, are large and have a 2+ charge, this means that the cation coordinated H2O will only be slightly acidic, ppt is seen at HIGH pH. Eg Ca(OH)2 ppt at pH above 12

78
Q

true or false, the higher the charge, the higher the enthalpy of hydration; as with increasing charge atomic radii decrease; more likelihood of deprotonation of water coordinated ligand to metal

A

true

79
Q

what is the pH of normal rain

A

5-6

80
Q

what is the pH of acid rain

A

3 or 4

81
Q

why are oxy anions soluble

A

this is because the central cation is so highly charged

82
Q

why are the neutral hydroxide complexes acidic when they form oxyanions

A

because the central charge is high that the complex is acidic

Environmental Chemistry (1 decks)

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