3.2.3 Group 7(17), the halogens Flashcards
1
Q
are halogens metals or non metals
A
non metals
2
Q
are halogens reactive
A
halogens are highly reactive
3
Q
what colour is fluorine
A
pale yellow
4
Q
what colour is chlorine
A
green
5
Q
what colour is bromine
A
red-brown
6
Q
what colour is iodine
A
grey
7
Q
physical state of fluorine
A
gas
8
Q
physical state of chlorine
A
gas
9
Q
physical state of bromine
A
liquid
10
Q
physical state of iodine
A
solid
11
Q
trend in boiling point for halogens:
what is the trend?
A
boiling point of halogens increases down the group
12
Q
trend in boiling point for halogens:
reasoning for the trend
A
strength of Van der Waals forces increases down the group as the size and relative mass of the molecules increases
13
Q
trend in electronegativity for halogens:
what is the trend?
A
electronegativity decreases down the group
14
Q
trend in electronegativity for halogens:
reasoning for the trend
A
larger atoms attract electrons less than smaller ones as outer electrons are further from the nucleus and more shielded, as they have more inner electrons
15
Q
in general, are halogens really electronegative
A
halogens are highly electronegative elements
16
Q
what happens when halogens react
A
when the halogens react, they gain an electron
17
Q
are halogens oxidising or reducing agents
A
halogens are oxidising agents
18
Q
trend in oxidising ability for halogens
what is the trend
A
halogens become less oxidising down the group
19
Q
trend in oxidising ability for halogens
explanation for trend
A
get less reactive down the group as atoms become larger and outer shells get further from the nucleus
20
Q
when will halogens displace a halide from solution
A
a halogen will displace a halide from solution if the halide is below it in the periodic table
21
Q
Displacement reactions
reaction between chlorine water and potassium chloride solution
A
no reaction
22
Q
Displacement reactions
reaction between bromine water and potassium chloride solution
A
no reaction
23
Q
Displacement reactions
reaction between iodine solution and potassium chloride solution
A
no reaction
24
Q
Displacement reactions
reaction between chlorine water and potassium bromide solution
A
orange solution (Br2) formed
25
Displacement reactions
reaction between bromine water and potassium bromide solution
no reaction
26
Displacement reactions
reaction between iodine solution and potassium bromide solution
no reaction
27
Displacement reactions
reaction between iodine solution and potassium iodide solution
no reaction
28
Displacement reactions
reaction between bromine water and potassium iodide solution
brown solution (I2) formed
29
Displacement reactions
reaction between chlorine water and potassium iodide solution
brown solution (I2) formed
30
what colour is chlorine water
colourless
31
what colour is bromine water
orange
32
what colour is iodine solution
brown
33
what colour is potassium chloride solution
colourless
34
what colour is potassium bromide solution
colourless
35
what colour is potassium iodide solution
colourless
36
what can displacement reactions be used to help with?
displacement reactions can be used to help identify which halogen (or halide) is present in a solution
37
what can displacement reactions be used to help with?
why?
halide ions are colourless in solution, but when the halogen is displaced it shows a distinctive colour
38
full equation for adding chlorine to potassium bromide
Cl2 (aq) + 2KBr (aq) = 2KCl(aq) + Br2(aq)
39
ionic equation for adding chlorine to potassium bromide
Cl2(aq) + 2Br-(aq) = 2Cl- (aq) + Br2(aq)
40
full equation for adding chlorine to potassium iodide
Cl2 (aq) + 2KI (aq) = 2KCl(aq) + I2(aq)
41
ionic equation for adding chlorine to potassium iodide
Cl2(aq) + 2I-(aq) = 2Cl- (aq) + I2(aq)
42
full equation for adding bromine to potassium iodide
Br2 (aq) + 2KI (aq) = 2KBr(aq) + I2(aq)
43
ionic equation for adding bromine to potassium iodide
Br2(aq) + 2I-(aq) = 2Br- (aq) + I2(aq)
44
why doesn't iodine displace either halide
it is below chlorine and bromine in group 7, so its less reactive than them so won't displace either halide
45
how to form sodium chlorate(I) solution
if you mix chlorine gas with cold, dilute sodium hydroxide solution at room temp, sodium chlorate(I) solution forms
46
chemical formula for sodium chlorate(I) solution and state symbol
NaClO (aq)
47
what is sodium chlorate(I) solution
common household bleach (kills bacteria)
48
what happens to chlorine in the reaction to form sodium chlorate(I) solution
chlorine is both oxidised and reduced
49
what is it called when chlorine is both oxidised and reduced
disproportionation
50
equation for forming sodium chlorate(I) solution
2NaOH(aq) + Cl2(g) = NaClO(aq) + NaCl(aq) + H2O(l)
NaCl and NaClO are the major products
51
in the equation for forming sodium chlorate(I) solution
what is the oxidation state of chlorine in Cl2
zero
52
in the equation for forming sodium chlorate(I) solution
what is the oxidation state of chlorine in NaClO
ClO- is the chlorate(I) ion, chlorine's oxidation state is +1
53
in the equation for forming sodium chlorate(I) solution
what is the oxidation state of chlorine in NaCl
-1
54
uses of sodium chlorate(I) solution
- water treatment
- cleaning
- to bleach paper and textiles
55
disproportionation equation for forming sodium chlorate(I) solution
Cl2(g) + H2O(l) = 2H+(aq) + Cl-(aq) + ClO-(aq)
(REVERSIBLE REACTION)
56
what can chlorine do to water in sunlight
in sunlight, chlorine can decompose water to form chloride ions and oxygen
57
equation for chlorine decomposing water in sunlight
Cl2(g) + H2O(l) = 2H+(aq) + 2Cl-(aq) + 0.5O2(g)
(REVERSIBLE REACTION)
58
what do chlorate(I) ions kill
bacteria
59
is chlorine toxic
yes, chlorine is toxic
60
chlorine and water treatment
chlorine is an important step of water treatment
61
why is chlorine an important step of water treatment (microorganisms)
kills disease causing microorganisms, some chlorine persists in the water and prevents reinfection further down the supply
62
why is chlorine an important step of water treatment (algae)
prevents the growth of algae, eliminating bad tastes/smells and removes discolouration caused by organic compounds
63
how is chlorine gas harmful
harmful if breathed in, irritates respiratory system
64
how is liquid chlorine harmful
liquid chlorine on the skin or eyes causes severe chemical burns
65
what does water contain a variety of
water contains a variety of organic compounds e.g. from the decomposition of plants
66
does chorine react with these organic compounds in the water
chlorine reacts with these organic compounds in the water to form chlorinated hydrocarbons e.g. chloromethane
67
risk of chlorinated hydrocarbons
many chlorinated hydrocarbons are carcinogenic (cancer causing)
68
why is it still okay to treat water with chlorine despite these risks
increased cancer risk is small compared to the risks of untreated water e.g. cholera
69
what charges do halide ions have
1-
70
do halide ions formed by gaining or losing electrons
gaining one electron
71
what happens when a halide on takes part in a redox reaction
halide reduces something else and is oxidised itself
72
trend in reducing power of the halides
reducing power of the halide increases down group seven
73
trend in reducing power of the halides explanation
ability for a halide to lose an electron depends on the attraction between the nucleus and outer electron. this attraction gets weaker down the group as the ions get larger so the outer electrons are further away from the positive nucleus, as well as more inner electrons so a greater shielding effect
74
do all halides react with concentrated sulfuric acid?
yes, they all give a hydrogen halide as a product to begin with
75
equation for initial reaction of halides with concentrated sulfuric acid
NaX(s) + H2SO4(l) = NaHSO4(s) + HX(g)
where X represents the halogen
76
what halogens only have one reaction with concentrated sulfuric acid
fluorine and chlorine
77
are the reactions of fluorine and chlorine with concentrated sulfuric acid redox reactions
they are not redox reactions
78
observations when fluorine or chlorine are added to concentrated sulfuric acid
misty fumes
79
general equation for reaction that occurs second when halides react with concentrated sulfuric acid
2HX(g) + H2SO4(l) = X2(g/s) + SO2(g) + 2H2O(l)
where X represents the halogen
Br2 is a gas
I2 is a solid
80
which halides undergo the 2nd reaction when they react with concentrated sulfuric acid
bromide and iodide
81
observations when NaBr is added to concentrated sulfuric acid
misty fumes and orange fumes of Br2
82
oxidation half equation for 2nd reaction when halides are added to concentrated sulfuric acid
2X-(g) = X2(s) + 2e-
halide(X) is oxidised
83
reduction half equation for 2nd rection when halides are added to concentrated sulfuric acid
H2SO4 + 2H+ + 2e- = SO2 + 2H2O
sulfuric acid is reduced
84
third reaction when halides react with concentrated sulfuric acid (iodide only)
6HI(g) + SO2(g) = H2S(g) + 3I2(s) + 2H2O(l)
85
observations when NaI is added to concentrated sulfuric acid
purple gas
86
why are there a different number of reactions based on what halide reacts with concentrated sulfuric acid
some halide ions are stronger reducing agents
87
testing for halides:
step 1
add dilute nitric acid to remove ions (hydroxide or carbonate) which might interfere with the test
88
testing for halides:
step 2
add a few drops of silver nitrate solution (AgNO3 aq). precipitate of the silver halide will form
89
testing for halides:
equation for silver nitrate test
Ag+(aq) + X-(aq) = AgX(s)
90
testing for halides:
why can't you use HCl instead of nitric acid
silver nitrate would react with the chloride ions from HCl which would mess up the results
91
testing for halides:
silver halide precipitate colours
chloride ions = white precipitate
bromide ions = cream precipitate
iodide ions = yellow precipitate
92
testing for halides:
step 3
split precipitates in half and add dilute ammonia solution to one half and concentrated ammonia solution to the other half
93
solubility of chloride ions in NH3 (aq)
chloride dissolves in dilute and concentrated NH3
94
solubility of bromide ions in NH3 (aq)
bromide dissolves in concentrated NH3 but not dilute NH3
95
solubility of iodide ions in NH3 (aq)
insoluble in concentrated and dilute NH3 so doesn't dissolve
96
how do you test for hydrogen sulphide (H2S)
- turns damp litmus red
- turns lead nitrate paper black
97
how do you test for sulphur dioxide (SO2)
-turns acidified potassium dichromate from orange to green
- turns damp litmus red
98
how to test for Cl2 gas
bleaches damp blue litmus paper
99
how to test for Br2
turns damp litmus red
100
equation for adding chlorine to water
(disproportionation)
Cl2(g) + H20(l) = HClO (aq) + HCl(aq)
reversible reaction and disproportionation reaction
101
equation for adding chlorine to water
2Cl2(g) + 2H2O(l) = 4HCl(aq) + O2(g)
102
equation for adding NaClO and H2O
NaClO(s) + H2O(l) = Na+(aq) + OH-(aq) + HClO(aq)
103
equation between AgCl and NH3
AgCl(s) + 2NH3(aq) → Ag(NH3)2+(aq) + Cl−(aq)
104
what is observed when silver nitrate is added to sodium fluoride solution
no visible change, no precipitate forms
105
when solid sodium chloride reacts with concentrated sulfuric acid what is the role of the chloride ions
base or proton acceptor
106
when solid sodium chloride reacts with concentrated sulfuric acid what is the role of the sulfuric acid
proton donor
107
overall equation for NaBr with sulfuric acid
2 NaBr + 2 H2SO4 → Na2SO4 + SO2 + Br2 + 2 H2O
108
Equation for sodium carbonate and nitric acid
Na2CO3 + 2HNO3 = 2NaNO3 + CO2 + H2O
109
Full equation for AgNO3 and NaCl
AgNO3 + NaCl = AgCl + NaNO3
