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AQA - A level Chemistry > Group 7 > Flashcards

Group 7 Flashcards

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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  • more shielding = reduce amount of electrons that can be withdrawn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

A

acidic

23
Q

Why is chlorine added to water?

A

to kill bacteria

24
Q

How is it possible to add chlorine to drinking water when chlorine is toxic?

A

only added at low concentrations

25
Q

Complete the overall equation for the reaction between sodium chlorate (I) and water

A

NaCl (aq) + H2O (l) —> Na+ (aq) + OH- (aq) + HClO (aq)

26
Q

Complete the overall equation to show the reaction of chlorine gas with an alkaline solution

A

Cl2 (aq) + 2NaOH (aq) —> NaCl (aq) + NaClO (aq) + H2O (l)

27
Q

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)”

A

iodide ions

28
Q

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.”

A

chloride ions

29
Q

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.”

A

fluoride ions

30
Q

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.”

A

bromide ions

31
Q

Select all the following observation(s) that would be present in the reaction with NaI(s) and H2SO4(aq).

A
  • acidic gas forms (SO2)
  • gas smelling of bad eggs formed (H2S)
  • black solid forms (I2)
  • yellow solid formed (sulfur)
32
Q

Solid sodium chloride reacts with concentrated sulfuric acid.
Give an equation for this reaction.
State the role of the sulfuric acid in this reaction.

A

NaCl + H2SO4 —> NaHSO4 + HCl
Proton donor

33
Q

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.

A

equation:
2NaBr + 2H2SO4 —> Na2SO4 + SO2

observation:
brown gas/brown fumes or orange gas/orange fumes

role:
oxidising agent

34
Q

Give the oxidation state of chlorine in NaClO3 and in NaCl

A

NaClO3
+5

NaCl
-1

35
Q

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.

A

M1 Misty or steamy or white fumes/gas
M2 NaCl + H2SO4 → NaHSO4 + HCl OR
2NaCl + H2SO4 → Na2SO4 + 2HCl M3 Base OR proton acceptor

36
Q

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.

A

M1 Misty or steamy or white fumes/gas
M2 NaCl + H2SO4 → NaHSO4 + HCl OR
2NaCl + H2SO4 → Na2SO4 + 2HCl M3 Base OR proton acceptor

37
Q

strongest oxidising agent

A

F-

38
Q

weakest oxidising agent

A

I-

39
Q

flouride with sulphuric acid

A

NaF (s) + H2SO4 (aq) —> NaHSO4 (s) + HF (g)
steamy fumes of HF gas produced

40
Q

chloride with sulphuric acid

A

NaCl (s) + H2SO4 (aq) —> NaHSO4 (s) + HCl (g)
steamy fumes of HCl gas

41
Q

bromide with sulphuric acid

A

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
Q

iodide with sulphuric acid

A

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
Q

testing for halides

A
  • add HNO3 to unknown sample
  • add few drops of silver nitrate solution
  • ppt forms
44
Q

fluoride ions test

A

NVC
AgF (aq)

45
Q

chloride ions test

A
  1. HNO3 and AgNo3
    white ppt AgCl (s)
  2. dilute ammonia
    white ppt dissolves
  3. conc ammonia
    white ppt dissolves
46
Q

bromine ions test

A
  1. HNO3 and AgNo3
    cream ppt AgBr (s)
  2. dilute ammonia
    cream ppt remains
  3. conc ammonia
    cream ppt dissolves
47
Q

iodide ions test

A
  1. HNO3 and AgNo3
    white ppt AgI (s)
  2. dilute ammonia
    yellow ppt remains
  3. conc ammonia
    yellow ppt remains
48
Q

uses of chlorine

A

kills bacteria

49
Q

chlorine and water

A

Cl2 (g) + H2O (l) —> HClO (aq) + HCl (aq)
- disproportionation
- chlorine goes through oxidation and reduction

50
Q

chlorine reaction in presence of sunlight

A

2Cl2 (g) + 2H2O (l) —> 4HCl (aq) + O2 (g)

cl2 = pale green
Hcl = colourless

51
Q

NaClO and H2O reaction

A

NaClO(s) + H2O(l) —> Na+(aq) + -OH(aq) + HClO(aq)
- reversible reaction
- added to swimming pools

52
Q

chlorine and sodium hydroxide reaction

A

Cl2 (g) + 2NaOH (aq) —> NaClO (aq) + NaCl (aq) + H2O (l)

AQA - A level Chemistry (25 decks)

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