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Chemistry > 10.Group 7, the halogens > Flashcards

10.Group 7, the halogens Flashcards

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1
Q

Describe the trend in size of atoms going down group 7

A
  • going down the group atoms get bigger

- each element has one extra filled main level of electrons

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2
Q

Describe the trend in electronegativity going down in group 7

A
  • electronegativity is the power of an atom to attract shared electrons in a covalent bond
  • going down the group electronegativity decreases
  • atoms get bigger and more shielding, going down a group
  • less nuclear attraction between halogen nucleus and shared electrons electrons in the covalent bond
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3
Q

Describe the trend in melting and boiling points going down in group 7

A
  • increase as you go down a group
  • larger atoms have more electrons
  • larger van der Waal forces
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4
Q

Define volatile

A

Easily evaporated at normal temperatures

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5
Q

Which is more volatile chlorine or iodine

A
  • the lower the boiling point the more volatile the element

- so chlorine is more volatile

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6
Q

Describe the trend in oxidising ability going down a group

A
  • going down a group the oxidising ability decreases
  • shielding and atom radii increases going down
  • nuclear attraction decreases
  • this reduces the ability for atom to attract (accept) electrons
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7
Q

How do halogens react with metal halides

A

By displacement reaction. Halide in the compound will be displaced by a more reactive halogen.

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8
Q

Write the ionic equation for the extraction of bromine from sea water

A

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

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9
Q

Describe how iodine is extracted from kelp

A
  • salts such as NaCl KCL and K2S04 are removed by washing with water
  • residue is then heated with manganese dioxide and conc. sulfuric acid and iodine is liberated
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10
Q

Write the ionic equation for the extraction of iodine from kelp

A

2I- +MnO2 + 4H+ —-> Mn2+ + 2H2O +I2

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11
Q

Describe the trend in reducing ability going down a group

A
  • going down a group the oxidising ability increases
  • shielding and atomic radii increases
  • reducing nuclear attraction
  • this increases the ability for atom to lose (donate) electrons
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12
Q

What reactions shows the trend in reducing ability

A

Reaction of solid sodium halides with conc. sulfuric acid

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13
Q

Name a observation when conc. sulfuric acid is added to NaCl

A

Steamy fumes of hydrogen chloride

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14
Q

Name the solid product when conc. sulfuric acid is added to NaCl

A

Hydrogensulfate

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15
Q

Write the equation for when conc. sulfuric acid is added to NaCl

A

NaCl (s) + H2SO4 (l) —> NaHSO4 (s) + HCl (g)

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16
Q

Is the reaction between conc. sulfuric acid and NaCl a redox reaction

A
  • no
  • as no oxidation state has changed
  • the chlorine ion is too weak a reducing agent to reduce the sulphur
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17
Q

What kind of reaction is the reaction between conc. sulfuric acid and NaCl

A

Acid-base reaction

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18
Q

Name a observation when conc. sulfuric acid is added to NaBr

A

Steamy fumes of hydrogen bromide and brown fumes of bromine

19
Q

What colour is bromine gas

A

Brown

20
Q

Describe two reactions that occur when conc. sulfuric acid is added to NaBr

A
  • first sodium hydrogensulfate and HBr are produced in an acid-base reaction
  • bromide ions are strong enough reducing agents to reduce sulfuric acid to sulfur dioxide
21
Q

Write the equations for when conc. sulfuric acid is added to NaBr and what reactions they are

A

1) NaBr (s) + H2SO4 (l) —-> NaHSO4 (s) + HBr (g)
an acid base reaction
2) 2H+ +2Br- + H2SO4 (l) —-> SO2 (g) + 2H2O (l) + Br2 (l)
a redox reaction

22
Q

Name a observation when conc. sulfuric acid is added to NaI

A
  • steamy fumes of HI
  • black solid of iodine
  • bad egg smell of hydrogen sulfide
23
Q

Describe two reactions that occur when conc. sulfuric acid is added to NaI

A
  • first sodium hydrogensulfate and HI are produced in an acid-base reaction
  • iodine ions are better reducing agents so reduce the sulfuric acid even further to sulfur dioxide sulfur and hydrogen sulfide are produced
24
Q

Write the equations for when conc. sulfuric acid is added to NaI and what reactions they are

A

1) NaI (s) + H2SO4 (l) —-> NaHSO4 (s) + HI (g)
an acid base reaction
2) 8H+ + 8I- + H2SO4 (l) —-> H2S (g) + 4H2O (l) + 4I2 (l)
a redox reaction

25
Q

Write an ionic equation for reaction of metal chlorides with silver ions

A

Cl- (aq) +Ag+ (aq) —->AgCl (s)

26
Q

Describe the steps in identifying metal halides with silver ions

A
  • dilute nitric acid is added to the solution to get rid of any soluble carbonate or hydroxide impurities
  • add a few drops of silver nitrate which forms the halide precipitate
27
Q

How would carbonates or hydroxides interfere with identifying metal halides with silver ions

A

-forming silver carbonate
2Ag+ (aq) + CO3 2- (aq) —-> Ag2CO3 (s)
-forming silver hydroxide
Ag+ (aq) + OH- (aq) —-> AgOH (s)

28
Q

Write the equations for getting rid of soluble carbonate or hydroxide impurities

A

CO3 2- (aq) + 2H+ (aq) —-> CO2 (g) + H2O (l)

OH- (aq) + H+ (aq) —-> H2O (l)

29
Q

What are the results form the identifying metal halides with silver ions test

A
  • silver fluoride :no precipitate
  • silver chloride: white precipitate
  • silver bromide: cream precipitate
  • silver iodide: pale yellow precipitate
30
Q

What further test can be done to distinguish silver halides

A
  • add a few drop of a dilute ammonia
  • then add a few drops of concentrated ammonia
  • silver chloride: dissolves in dilute ammonia
  • silver bromide: dissolves in conc. ammonia
  • silver iodide: insoluble in conc. ammonia
31
Q

Write the equation for the reaction between chlorine and water

A

Cl2 (g) +H2O (l) —> HClO (aq) + HCl (aq)

32
Q

What kind of reaction is the reaction between chlorine and water

A

Disproportionation

33
Q

What is a disproportionation reaction

A

Describes a redox reaction in which the oxidation number of some atoms of a particular element increases and that of other atoms of the same atom decrease

34
Q

Name a use for the reaction between chlorine and water

A

Purify drinking water and swimming baths as the chloric acid kills bacteria by oxidation (as it is an oxidising agent)
It is also a bleach

35
Q

Describe the reaction between chlorine and water in sunlight

A

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

pale green —-> colourless

36
Q

Describe an alternative to the direct chlorination of swimming pools

A

-add solid sodium (or calcium) chlorate (I). This dissolves in water to form chloric acid, HClO (aq)

37
Q

Write an equation for sodium chlorate and water

A

NaClO (s) + H2O Na+ (aq) + OH- + HClO (aq)

38
Q

Why do swimming pools with sodium chlorate dissolved need to be slightly acidic

A

-in alkaline solution the equilibrium moves to the left and the HClO is removed as ClO-

39
Q

Write the equation for the reaction with chlorine and alkali

A

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

40
Q

Describe the reaction for the reaction with chlorine and alkali

A

Chlorine reacts with cold, dilute sodium hydroxide to form sodium chlorate (I), NaClO.

41
Q

What is NaClO

A
  • oxidising agent

- active ingredient in household bleach

42
Q

What kind reaction of is the reaction with chlorine and alkali

A

Disproportionation

43
Q

Name two disproportionation reactions

A
  • chlorine + alkali

- chlorine + water

Chemistry (27 decks)

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