T2 HALOGENS Flashcards
(87 cards)
1
Q
What is the electronic configuration of the halogens?
A
The electronic configuration is ns² np⁵.
2
Q
What type of ions do halogens form?
A
They form very stable mononegative ions.
3
Q
How are halogens found in their elemental state?
A
They form diatomic molecules by sharing the unpaired electron.
4
Q
What is the standout property of halogens in terms of reactivity?
A
They have a strong oxidizing power.
5
Q
What happens to the ionization energies of halogens as they move from left to right in the group?
A
They increase due to the increase in effective nuclear charge.
6
Q
What is the most electronegative element in the periodic table?
A
Fluorine (F) is the most electronegative.
7
Q
Why do halogens exhibit different colors?
A
Due to a shift in light absorption towards higher wavelengths.
8
Q
What effect does atomic size have on the dissociation energy of halogens?
A
It decreases down the group, except for F2 due to interelectronic repulsions.
9
Q
What color of light is absorbed by iodine?
A
Yellow.
10
Q
How does the electron affinity of halogens vary as they descend in the group?
A
It increases, except for fluorine due to interelectronic repulsions.
11
Q
Which element has the highest electron affinity in the group?
A
Fluorine.
12
Q
What happens to the free energy of hydration as you go up the group?
A
It decreases due to the lower charge density of large anions.
13
Q
How does the redox potential of halogens change?
A
It decreases and has a very high and anomalous value for fluorine.
14
Q
What is the best oxidant in the halogen group?
A
F2.
15
Q
What is the best reductant in the halogen group?
A
I-.
16
Q
In which medium is the oxidizing power higher: acidic or basic?
A
It is always higher in acidic medium.
17
Q
How it increase size in halogens?
A
Down
18
Q
How it increase ionization energy in halogens?
A
up
19
Q
How it increase electronegativity in halogens?
A
up
20
Q
How it increase the bond. MP and BP in halogens?
A
down
21
Q
Why is fluorine considered a “superhalogen”?
A
Due to its small size, which makes it highly reactive and electronegative.
22
Q
Which elements does fluorine not react with?
A
It does not react with helium (He) or neon (Ne).
23
Q
What compounds can’t F2 extract?
A
It cannot extract H2 except in the case of HF.
24
Q
How does F2 react with metals?
A
It forms fluorides with all metals; however, some, such as Cu, Ni, Al, and Fe, passivate due to the formation of MF2.
25
What type of bond does fluorine form with the greatest strength?
It forms the strongest hydrogen bonds due to its high electronegativity.
26
Why is the F-F bond weaker than expected?
The non-bonding electronic repulsion of the F atoms in the molecule due to their small size.
27
What is the difference in the oxidizing power of F2 compared to other halogens?
The oxidizing power of F2 is much greater due to the weakness of the F-F bond and the higher hydration energy of the F- anion.
28
What causes fluorides to have higher lattice energy (U) compared to other halides?
The small size of the F- anion.
29
Why does fluorine form the strongest covalent bonds?
Due to its small size, which allows for better orbital overlap, and its high electronegativity.
30
What is the main difference in the solubility of fluorides compared to other halides?
Fluorides have different solubility due to their ionic nature, bond limitations of fluorine, and low polarizability.
31
How is fluorine (F2) obtained, and what is its abundance in Earth's crust?
Fluorine is obtained from fluorite (CaF2), and it's the 13th most abundant element in Earth's crust.
32
Why is obtaining F2 in aqueous solution impossible, and how is F2 obtained through electrolysis?
F2 oxidizes H2O to O2, making aqueous production impossible. It's obtained via electrolysis of HF(g) dissolved in molten KF.
33
How is chlorine (Cl2) currently obtained and what are the key methods used in industry?
Cl2 is obtained from seawater's NaCl through electrolysis. Different methods include the mercury cell, diaphragm cell, and Downs cell.
34
Explain the three electrolytic setups used in chlorine production.
The setups include the mercury cell, diaphragm cell, and Downs cell, differing in how they separate the anode and cathode.
35
How is bromine (Br2) obtained?
Br2 is obtained by oxidizing seawater's Br– with Cl2
36
What is the source of iodine (I2), and how is it extracted from natural sources?
I2 is sourced from algae and seawater, extracted by oxidizing I– with Cl2.
37
How do the reactivities of F2 and Cl2 compare with other elements?
F2 reacts with all elements except He and Ne, while Cl2 is highly reactive and chlorinates organic compounds.
38
What trend is observed in the oxidizing power of halogens?
The oxidizing power decreases along the series Cl2 > Br2 > I2.
39
How does iodine's solubility in water differ from other halogens?
Iodine is slightly soluble in water but dissolves better in aqueous KI solution.
40
How does the reactivity of halogens change across the series from Cl2 to I2?
Chemical reactivity decreases from Cl2 to I2, particularly in reactions with H2, P4, S8, and most metals.
41
What are halides, and what distinguishes them?
Halides are binary compounds of halogens. They exhibit varied characteristics based on their type: ionic, covalent, or intermediate.
42
Describe the characteristics of ionic halides.
Ionic halides typically form 3D compounds with high melting and boiling points. They involve less electronegative elements and have very electropositive metals.
43
What are the properties of covalent halides?
Covalent halides are volatile molecular compounds, usually gases or liquids at ambient conditions. Their melting and boiling points increase with the number of electrons.
44
Explain the features of intermediate halides.
Intermediate halides, formed with elements of intermediate electronegativities, exhibit low-dimensional structures like chains and planes. They possess characteristics between purely covalent and ionic halides.
45
What are the methods for synthesizing halides?
Halides can be synthesized through direct reaction from elements, reactions of oxides and hydroxides with HX, reactions of oxides with covalent halides, and halogen exchange reactions.
46
How are halides synthesized directly from elements?
Direct reaction from elements works well for s-block metals. For groups 13 and 14, it's used with Cl2, Br2, and I2. In groups 15 and 16, reaction with F2 produces high oxidation states, while with heavier halogens, it produces low oxidation states.
47
Describe the synthesis of halides using reactions of oxides and hydroxides with HX.
This method is useful for synthesizing metal halides, including transition metals. Ionic halides can be synthesized from the metal and the corresponding hydrogen halide.
48
How are halides prepared using reactions of oxides with covalent halides?
This method is useful for preparing several chlorides and fluorides.
49
What are halogen exchange reactions, and how are they employed?
Halogen exchange reactions, like SnF4, are used to prepare fluorides from chlorides. The general rule is that the more electronegative halide combines with the less electronegative central.
50
Provide examples of when each synthesis method is commonly used.
- Direct reaction from elements is used for alkali and alkaline earth metals.
- Reactions with oxides and hydroxides are common in transition metal chemistry.
- Reactions with covalent halides are employed for specific compounds.
- Halogen exchange reactions are utilized in various industrial processes.
51
What happens when Cl–, Br–, and I– ions are dissolved in water?
They are soluble in water, forming hydrohalic acids.
52
What happens when most covalent halides react with water?
They react violently to give hydroxides, oxides, or oxoacids.
53
Why are some fluorides inert, like CF4 and SF6?
The E–F bond is very strong.
54
How does the solubility of F– compare to other halides?
Ionic F– has poorer solubility due to its smaller ionic radius, leading to higher lattice energy.
55
What are some applications of fluoride?
Fluoride is used in water to prevent tooth loss and in toothpaste. Fluorine-containing compounds are used in ceramic industries to increase the fluidity of molten glass.
56
How is bromide used in photography?
It has been used in photographic films for 150 years to reduce Ag+ to Ag0 in the presence of light, forming black spots.
57
How is iodide used in table salt?
KI (iodised salt) is added to prevent goiter.
58
What are the characteristics of hydrogen halides?
They are colorless gases, and their solutions in water are hydrohalic acids. Boiling and melting points increase down the group.
59
How does the acidity of hydrogen halides change down the group?
It increases from F to I due to weakening of the X–H bond.
60
How can hydrogen halides be synthesized?
They can be obtained by direct combination of the corresponding halogen with H2 or by reaction of an acid with the corresponding halide.
61
escribe the properties and uses of HF.
HF is a very toxic liquid with strong hydrogen bonds. It's used in uranium enrichment, oil refineries, synthesis of organofluorine compounds, and glass etching.
62
What are the properties and uses of HCl?
Highly soluble in water, HCl is formed by protonation of Cl– and is used in steel cleaning, synthesis of NH4Cl, CLO2, and organochlorine compounds.
63
What makes ClO2 unique among halogen oxides?
ClO2 is the only halogen oxide produced at large scale and is a very strong oxidant.
64
How is ClO2 used in the paper industry?
It's used for pulp bleaching and in water treatment due to its efficient disinfection properties.
65
What are the advantages and disadvantages of using ClO2 over Cl2?
ClO2 is 30 times more efficient than Cl2 and doesn't generate chloramines, but it can be explosive.
66
What do frost diagrams show about halogen species?
They illustrate that all species are more oxidant in acidic conditions and halides are the most stable species in any condition.
67
How do oxidation state and halogen size affect redox reaction rates?
Redox rates decrease as oxidation state increases, while for the same oxidation state, rates increase with halogen size.
68
How does the acidity of oxoacids change with the number of oxygen atoms bonded to the halogen?
Acidity increases with the number of oxygen atoms bonded to the halogen, depending on the oxidation state of X.
69
What are the properties and uses of chlorine oxoacids?
Chlorine forms various oxoacids like HClO, ClO–, and HClO4, used in bleaching, disinfection, and as strong oxidizing agents.
70
Describe the properties and uses of bromine oxoacids.
Bromine oxoacids like HBrO and HBrO3 are used as bleaching and disinfectant agents, and KBrO3 is used in volumetric analysis.
71
What are the characteristics of iodine oxoacids?
Iodine oxoacids include HIO and HIO3, which are weaker acids compared to chlorine and bromine oxoacids, and HIO4 is a strong oxidant.
72
What are the properties and hazards of perchloric acid?
HClO4 is the strongest simple acid, highly explosive, and used as a powerful oxidizing agent. Perchlorate salts are also explosive.
73
What are the most stable species in halogens?
-1
74
What halogens can be oxidize?
Only heavy halogens
74
The undergo dismutation in 0 is more favorable in...
basic media
75
Halogens +1 also undergo...
disproportionation
76
HCLO4 and HIO4 anions are...
strong oxidants
77
What is fluorine primarily used for in the nuclear industry?
Fluorine is used in the enrichment of uranium isotopes, particularly in the production of nuclear fuels for weapons and energy generation.
78
How does fluorine contribute to the production of high-temperature-resistant plastics?
Fluorine is a component in many plastics, including Teflon, due to its small size and high covalence, providing properties like temperature resistance.
79
What is the primary application of chlorine in the chemical industry?
Chlorine is predominantly used in the synthesis of organochlorine compounds like disinfectants, insecticides, herbicides, and PVC, among others.
80
How is chlorine utilized in the disinfection of water?
Chlorine gas is commonly used to disinfect drinking water, wastewater, and swimming pools, where it forms hypochlorite, a potent oxidizing agent that kills bacteria.
81
What role does bromine play in the production of flame-retardant materials?
Bromine is utilized as a flame retardant in carpets and plastics, providing protection against fire hazards.
82
How is iodine employed in the pharmaceutical industry?
Iodine is used in pharmaceutical synthesis to produce drugs, disinfectants, and radiocontrast agents, among other compounds.
83
What is the role of fluoride in dental care products like toothpaste?
Fluoride, often in the form of NaF or sodium monofluorophosphate, is added to toothpaste to reduce tooth demineralization and prevent cavities.
84
What are the health risks associated with chlorine exposure?
Chlorine gas is toxic, causing irritation to the skin, eyes, and respiratory system, with serious health effects even at low concentrations.
85
How is methyl bromide used in agriculture?
Methyl bromide is utilized as a fumigant pesticide in soils and packaging to control pests and preserve crops.
86
What role does iodine play in the human body, particularly in thyroid health?
Iodine is essential for thyroid hormone synthesis and function, regulating metabolism and growth, with deficiency leading to various health problems.
