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AQA - A level Chemistry > Group 7 > Flashcards

Group 7 Flashcards

1
Q

Identify a reagent that could be used to indicate the presence of iodide ions in an aqueous solution and describe the observation made.

A

AgNO3 yellow ppt
or
Cl2 or Br2brown solution/black ppt

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2
Q

What type of molecules are group 7 under normal conditions?

A

Diatomic molecules e.g. F2, Cl2, Br2

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3
Q

What are group 7 ions called?

A
  • When they gain an electron to form 1- ions
  • called halides e.g. F-, Cl-, Br-
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4
Q

Describe fluorine at room temperature

A

pale yellow gas

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5
Q

Describe chlorine at room temperature

A

pale green gas

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6
Q

Describe bromine at room temperature

A
  • orange/brown liquid
  • vaporises easily into an orange gas
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7
Q

Describe iodine at room temperature

A
  • black solid
  • vaporises to purple gas when heated
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8
Q

describe what happens to group 7 elements as you go down the group?

A

become darker and denser

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9
Q

describe trend in atom size as you go down group 7

A
  • atoms get bigger
  • shielding increases
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10
Q

describe trend in electronegativity as you go down group 7

A

electronegativity decreases

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11
Q

what 3 factors does electronegativity of group 7 elements rely on?

A
  • nuclear charge
  • atomic radius
  • shielding
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12
Q

How does nuclear charge, atomic radius and shielding affect electronegativity?

A
  • greater nuclear charge = withdraw electrons more strongly
  • shorter atomic radius = helps withdraw electrons more strongly
  • more shielding = reduce amount of electrons that can be withdrawn
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13
Q

What is the most electronegative element of group 7?

A

Fluorine

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14
Q

What is the least electronegative element of group 7?

A

Iodine

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14
Q

What type of IMF exists between group 7 molecules?

A

Van Der Waals

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15
Q

What can halogens act as?

A

Oxidising agents

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16
Q

What is the strongest oxidising agent of group 7?

A
  • Fluorine
  • accepts electrons most easily
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17
Q

What is the weakest oxidising agent of group 7?

A
  • Iodine
  • accepts electrons least easily
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18
Q

What happens during displacement reactions?

A
  • highest element in group 7 forms halide ion
  • halogen lowest down group 7 forms halogen molecule
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19
Q

Displacement reaction between chlorine and sodium bromide

A

Cl2 (aq) + 2NaBr (aq) —> 2NaCl (aq) + Br2 (aq)

OR

Cl2 (aq) + 2Br (aq) —> 2Cl- (aq) + Br2 (aq)

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20
Q

Reaction between potassium fluoride and chlorine

A
  • no reaction
  • F is higher than Cl
  • F exists as ions
  • Cl exists as molecules
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21
Q

Chlorine reacts with cold, dilute, aqueous sodium hydroxide.
Give a complete list of the names of the products?

A
  • sodium chlorate (I)
  • sodium chloride
  • water
22
Q

What type of solution is formed when chlorine is added to water

23
Q

Why is chlorine added to water?

A

to kill bacteria

24
How is it possible to add chlorine to drinking water when chlorine is toxic?
only added at low concentrations
25
Complete the overall equation for the reaction between sodium chlorate (I) and water
NaCl (aq) + H2O (l) ---> Na+ (aq) + OH- (aq) + HClO (aq)
26
Complete the overall equation to show the reaction of chlorine gas with an alkaline solution
Cl2 (aq) + 2NaOH (aq) ---> NaCl (aq) + NaClO (aq) + H2O (l)
27
What halide would be present following these observations? "To the unknown sample, a few drops of nitric acid (HNO3) were added. Following this, a few drops of Silver Nitrate solution (AgNO3) were added and a yellow precipitate was formed. This precipitate remained after the addition of dilute and concentrated ammonia (NH3)"
iodide ions
28
What halide would be present following these observations? "To the unknown sample, a few drops of nitric acid (HNO3) were added. Following this, a few drops of Silver Nitrate solution (AgNO3) were added and a white precipitate was formed."
chloride ions
29
What halide would be present following these observations? "To the unknown sample, a few drops of nitric acid (HNO3) were added. Following this, a few drops of Silver Nitrate solution (AgNO3) were added and no precipitate was observed forming."
fluoride ions
30
What halide would be present following these observations? "To the unknown sample, a few drops of nitric acid (HNO3) were added. Following this, a few drops of Silver Nitrate solution (AgNO3) were added and a cream precipitate formed. This precipitate remained upon addition of dilute ammonia (NH3). but dissolved when concentration ammonia was added."
bromide ions
31
Select all the following observation(s) that would be present in the reaction with NaI(s) and H2SO4(aq).
- acidic gas forms (SO2) - gas smelling of bad eggs formed (H2S) - black solid forms (I2) - yellow solid formed (sulfur)
32
Solid sodium chloride reacts with concentrated sulfuric acid. Give an equation for this reaction. State the role of the sulfuric acid in this reaction.
NaCl + H2SO4 ---> NaHSO4 + HCl Proton donor
33
Fumes of sulfur dioxide are formed when sodium bromide reacts with concentrated sulfuric acid. For this reaction * give an equation * give one other observation * state the role of the sulfuric acid.
equation: 2NaBr + 2H2SO4 ---> Na2SO4 + SO2 observation: brown gas/brown fumes or orange gas/orange fumes role: oxidising agent
34
Give the oxidation state of chlorine in NaClO3 and in NaCl
NaClO3 +5 NaCl -1
35
State one observation when solid sodium chloride reacts with concentrated sulfuric acid. [1 mark] [3 marks] 0 9 . 3 Give an equation for the reaction. State the role of the chloride ions in the reaction.
M1 Misty or steamy or white fumes/gas M2 NaCl + H2SO4 → NaHSO4 + HCl OR 2NaCl + H2SO4 → Na2SO4 + 2HCl M3 Base OR proton acceptor
36
State one observation when solid sodium chloride reacts with concentrated sulfuric acid. Give an equation for the reaction. State the role of the chloride ions in the reaction.
M1 Misty or steamy or white fumes/gas M2 NaCl + H2SO4 → NaHSO4 + HCl OR 2NaCl + H2SO4 → Na2SO4 + 2HCl M3 Base OR proton acceptor
37
strongest oxidising agent
F-
38
weakest oxidising agent
I-
39
flouride with sulphuric acid
NaF (s) + H2SO4 (aq) ---> NaHSO4 (s) + HF (g) steamy fumes of HF gas produced
40
chloride with sulphuric acid
NaCl (s) + H2SO4 (aq) ---> NaHSO4 (s) + HCl (g) steamy fumes of HCl gas
41
bromide with sulphuric acid
NaBr (s) + H2SO4 (aq) ---> NaHSO4 (s) + HBr (g) 2Br- ---> Br2 + 2e- 2H+ + H2SO4 + 2e- --> SO2 + 2H2O OVERALL EQUATION 2br- + 2h+ + H2so4 ---> br2 + so2 + 2h2o
42
iodide with sulphuric acid
NaI (s) + H2SO4 (aq) ---> NaHSO4 (s) + HI (g) 1. 2I- ---> I2 + 2e- 2H+ + H2SO4 + 2e- --> SO2 + 2H2O overall equation 2H+ + H2SO4 + 2I- ---> SO2 + 2H2O + I2 acidic gas and black iodine solid forms 2. 2I- ---> I2 + 2e- 6H+ + H2SO4 + 6e- --> S + 4H2O overall equation 6I- + H2SO4 + 6H+ ---> 3I2 + S + 4H2O yellow solid sulfur and black iodine solid forms 3. 2I- ---> I2 + 2e- 8H+ + H2SO4 + 8e- ---> H2S + 4H2O overall equation 4I- + 8H+ + H2SO4 ---> H2S + 4I2 + 4H2O gas smelling of bad eggs and black iodine solid forms
43
testing for halides
- add HNO3 to unknown sample - add few drops of silver nitrate solution - ppt forms
44
fluoride ions test
NVC AgF (aq)
45
chloride ions test
1. HNO3 and AgNo3 white ppt AgCl (s) 2. dilute ammonia white ppt dissolves 3. conc ammonia white ppt dissolves
46
bromine ions test
1. HNO3 and AgNo3 cream ppt AgBr (s) 2. dilute ammonia cream ppt remains 3. conc ammonia cream ppt dissolves
47
iodide ions test
1. HNO3 and AgNo3 white ppt AgI (s) 2. dilute ammonia yellow ppt remains 3. conc ammonia yellow ppt remains
48
uses of chlorine
kills bacteria
49
chlorine and water
Cl2 (g) + H2O (l) ---> HClO (aq) + HCl (aq) - disproportionation - chlorine goes through oxidation and reduction
50
chlorine reaction in presence of sunlight
2Cl2 (g) + 2H2O (l) ---> 4HCl (aq) + O2 (g) cl2 = pale green Hcl = colourless
51
NaClO and H2O reaction
NaClO(s) + H2O(l) ---> Na+(aq) + -OH(aq) + HClO(aq) - reversible reaction - added to swimming pools
52
chlorine and sodium hydroxide reaction
Cl2 (g) + 2NaOH (aq) ---> NaClO (aq) + NaCl (aq) + H2O (l)

AQA - A level Chemistry (25 decks)

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