T1 HYDROGEN Flashcards
(115 cards)
1
Q
The existence of life depends o twoparticular properties of hydrogen that are..
A
- The closeness of the electronegativity of carbon and hydrogen
- The ability of hydrogen to form hydrogen bonds when covalently bonded to N or O.
2
Q
How do alkali metals react with water? and hydrogen is the same?
A
Violently (and hydrogen does not)
3
Q
Does hydrogen have oxidizing power?
A
NO
4
Q
What are the reasons why hydrogen should be place with the Alkali metals?
A
- 1s1
- Metallic at high P
- Forms H+
5
Q
What are the reasons why hydrogen should be place with the halogens?
A
- Non-metal
- Diatomic molecule
- C - H bonds
6
Q
Where should hydrogen be place in the periodic table?
A
In the middlemof the periodic table.
7
Q
What is the abundance of hydrogen in the Universe? And in earth?
A
Most abundance in the universe, 3rd most abundance on earth.
8
Q
What are the 3 more important Isotopes of hydrogen?
A
- PROTIUM
- DEUTERIUM (D)
- TRITIUM (T)
9
Q
How many neutrons does hydrogen have?
A
0
10
Q
How many neutrons does deuterium have?
A
1
11
Q
How many neutrons does tritium have?
A
2
12
Q
What is more abundant H2, D2 or T2?
A
ABUNDANCE:
H2»_space;> D2»_space; T2
13
Q
With have the higher melting and boiling point H2, D2 or T2?
A
T2
14
Q
D and T form stronger bonds with other elements or with H?
A
With other elements
15
Q
D and T are used as markers to follow the reaction mechanism where there is a….., determining the isotopic composition by….
A
transfer of H or H2O/ NMR, IR or mass spectrometry.
16
Q
H2 can be obtain by different methods such as….
A
- Reduction of H2O
- Electrolysis of H2O
- Steam reforming of natural gas
- Coal gasification
- Thermochemical water splitting
- Direct photoelectrochemical water splitting
- Biological processes
- Cloroalkali process
- Cracking process
17
Q
The reduction of H2O metho consist in preparing H2 by…
A
reduction of H20 with a reducing agent, normally Zn.
18
Q
The electrolysis method is done using…
A
H2SO4 as an electrolyte.
19
Q
The method of coal gasification is perform by…
A
passing steam and oxygen over coal in the presence of a catalyst.
20
Q
The method of thermochemical water splitting uses….., to drive a series of….
A
high temperatures from solar or nuclear power plants / chemical reactions to produce hydrogen.
21
Q
The method of direct photoelectrochemical water splitting uses…
A
semiconductors materials to produce potential that electrolyzed water.
22
Q
The biological processes to produce H2 is done by…
A
some microorganism that digest and realease hydrogen in the dark fermentation process.
23
Q
The cloroalkaliprocess produce…
A
chlorine and sodium hydroxide from electrolysis of NaCL solution.
24
Q
The cracking process is important in the production of…
A
petrol.
25
In the cracking process a common reaction is the...
alkane deshydrigenation.
26
Physical properties of H2
- Colorless gas
- Odorless gas
- Lowest density of all
27
H2 is relatevely inert due to...
high H-H bonding
28
What bonds are the only ones that are higher than the H-H bond?
H-O
H-F
(Thats why H2 reacts violently with F2 and O2)
29
At high T, H2 can reduce some...
metals oxides to the elemtent.
30
With a catalyst H2 reduces....
doble and triple bonds to simple bonds.
31
Is H2 reactive at ambient conditions?
Nor very
32
What is the origin of the lack of reactivity of H2?
Kinetic origin caused by the strengh of the H-H bond.
33
The interaction between the surface of a catalyst and H2 .... and allows it to break.
weakens the H-H bond
34
H2 can undergo reactions through 2 possible activation mechanisms:
1. HOMOLYTIC CLEAVAGE
2. HETEROLYTIC CLEAVAGE
35
The homolytic cleavage occurs at the surface of ...
Pd and Pt.
36
The homolytic cleavage is important in the...
catalytic hydrogenation of alkenes and other organic compounds.
37
What is produced in the homolytic cleavage with halogens?
A radical chain
38
The heterolytic cleavage occurs on the surface of...
Cu and Zn
39
The heterolytic cleavage is important in the...
catalytic conversion of CO methanol.
40
What is the reaction of the homolytic cleavage?
H2 --> 2 H+
41
What is the reaction of the heterolytic cleavage?
H2 --> H+ + H-
42
Applications of hydrogen:
1. Synthesis of NH3
2. Hydrogenation of unsaturated fats and oils
3. Reduction of metallic oxides
4. Production of MeOH
5. Hydrodealkylation reactions
6. Hydrodesulfurization
7. Hydrocracking
8. Production of HCL
9. Welding
10. Coolant
11. Liquid propellant
12. Ballons and airships
43
What is the main use of H2?
Synthesis of NH3
44
How is name the process of synthesis de NH3 using H2?
Haber-Bosch process in the presence of a Fe catalyst.
45
The Haber-Bosch reaction has a ...
high activation energy
46
NH3 is the starting material in the...
fertilizer industry and the fabrication of explosives.
47
The hydrogenation of unsaturated fats and oils is use to produce...
margarine and soaps.
48
The hydrodesulfurization is a very important process in...
petrocheistry.
49
The hydrocracking is the breaking of..
C-C bonds using hydrogen at high pressures.
50
H2 has the highest thermal conductivity of any gas?
YES
51
Deuterium is use as...
moderator in nuclear fission reactors.
52
Deuterated solvents are used in...
NMR spectroscopy
53
Tritium is used in combination with phosphors in...
self-powered lighting devices, and in nuclear weapons.
54
Hydrogen is a promising energy vector because of it....
- High energy density
- Huge amounts of hydrogen in seawater
- Combustion is harmless
55
The problem in usng H2 as a energy source is that is not a...
natural fuel, it cost energy. And storage is also a problem.
56
To storage liquid H2 you need...
very low temperatures and high pressures.
57
Fuel cells directly transform the....
energy of chemical bonds into electrical energy.
58
In fuel cell what is in the anode and what in the cathode?
H2 is introduced in the anode and O2 in the cathode.
59
In fuel cells electrons travell...
from anode to cathode generating an electric current. Protons migrate in the same direction
60
Which is the element that form the most combinations with other elements?
H
61
Binary compounds of hydrogen are named...
hybrides
62
What types of hybrides are? And which elements are involve in its?
1. IONIC HYBRIDES OR HYDRIDE SALTS (Very electropositive metals, group 1 and 2)
2. INTERSTITIAL OR METAL HYBRIDES (Transition metals mainly groups 3 to 5)
3. COVALENT OR MOLECULAR HYBRIDES (Non-metals, p block escept noble gasses)
63
In ionic hybrides H is found as...
H-
64
Ionic hybrides are...
very reactive white solids.
65
What type of structures does group 1 hybrides have?
NaCl crystal structure
66
The hybride anion is a...
very strongh base.
67
Ionic hybrides anions are use in...
synthesis in order to dry organic solvents.
68
Suspensions of NaH are used as a...
strong basee and as reducing agents.
69
Pt does not form metal hybrides due to...
higher bond energy.
70
Metal hybrides are form by...
warming the metal with hydrogen at high pressure.
71
At high temperatures the hybrides release the...
hydrogen
72
Metallichybrides have a...
luster and high conductivity.
73
The conductivity of metal hybrides is due to free electrons but is less than the conductivity of...
pure metals
74
Metal hybrides have lower density what results in...
brittleness
75
Applications of metal hybrides?
1. H2 STORAGE
2. H2 PURIFICATION
3. BATTERIES
76
Metal hybrides are use for the storage of H2 because they are able to...
absorb and realease huge amounts of H2.
77
The high mobility of H2 in these MH is used to...
purify H2 gas.
78
What type of hydrides are use in recharchable batteries in portable devices?
Nickel metal hybrides
79
Batteries are based on....
metal alloys that absorb and release H.
80
The alloys combine ...
one endothermic metal and one exothermic one.
81
Covalent metals classifies according to electronegativity in...
1. Neutral covalent hybrides
2. Hybrides with positive polarity of the H atoms
3. Hybrides with negative polarity of the H atoms
82
Neutral covalent hybrides are the ones with...
same electronegativity
83
Caracteristics of neutral covalent hybrides:
- Low BP
- Unstable towards air conditions
84
Example of neutral covalent hybrides?
PH3, CH, H2Se, hydrocarbons
85
Caracteristics of hybrides with positive polarity of the atom?
- Stable in air
- High MP and BP (abnormally high)
86
An important class of hybrides with negative polarity of the H atom are?
Boron hydrides
87
BH3 can not be obtain in...
pure form
88
The molecular structure of the hybrides with negative polarity of the H atom of the group 14 is...
tetrahedral
89
The molecular structure of the hybrides with negative polarity of the H atom of the group 15 is...
Trigonal pyramidal
90
The molecular structure of the hybrides with negative polarity of the H atom of the group 16 is...
Angular
91
What are the types of synthesis of hybrides?
1. Direct combination
2. Protonation of a bronsted basic anion
3. Reaction of an ionic hybride with a halide (metathesis)
92
The method of direct combination of the elements is useful when the compounds have...
negative Gibbs energies of formation.
93
What are the 3 types of reactivity of molecular hybrides?
1. Heterolytic cleavage with hybride transferm
2. Homolytic cleavage
3. Heterolytic cleavage with proton transfer
94
Acid strengh increases from...
right to left and top to bottom
95
What are the 3 types of reactivity of ionic hybrides?
1. Metathesis with a halide
2. Addition to a lewis acid
3. Reaction with a proton source, to produce H2
96
The hydrogen bond is a....
special kind of dipole-dipole interaction between hydrogen and N,O,F.
97
Hydrogen bonds are form by...
polar groups on one side and atoms with negative charge on the other
98
What is the distance (d)
Distance between the H and the acceptor atom.
99
What is the distance (D)
Distance between the aceptor and the donor
100
Hydrogen bonding can be regarded as the first step of a...
proton-transfer reaction.
101
Strong H bonds have a...
linear geometry
102
Enegy of a hydrogen bond is to largo to be a...
dipole-dipole interaction
103
What is the strongest hydrogen bond?
F -H -F
104
Peculiar properties of water are due to the...
hydrogen bond
105
The large difference in electronegativity between O and H atoms makes the O-H bond...
strongly polar.
106
What bonds form the H20?
4 bonds, two with donor and 2 with acceptors.
107
The structure of ice is an...
open structure
108
The hydrogen bond are responsable of....
1. Large surface tension of water
2. High melting and boiling points
3. High capillarity force
4. High specific heat
5. High heat of vaporization
109
O-D bonds are ..... than O-H
more stable
110
O-D...A bonds are.... than O-H...A
weaker
111
What is bond cooperativity?
Is the fact that a bond with an atom A makes the O-H bond more polar and stronger.
112
D-H groups may also be polarized by ....
charge flow through pi bonds.
113
An amide group becomes a stronger proton donor if the carbonyl group acts as....
a proton acceptor
114
The effect of the amide group becoming stronger is due to... and can be explain through the... this is called....
polarization of s bond / planar resonance structure / p-bond cooperativity
115
The p-bond cooperativity is very important in the...
secondary structure of proteins.
