The halogens Flashcards

1
Q

What is the colour and state of fluorine at room temperature?

A

Pale yellow gas

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2
Q

What is the colour and state of chorine at room temperature?

A

Pale greenish gas

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3
Q

What is the colour and state of bromine at room temperature?

A

Red/brown liquid

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4
Q

What is the colour and state of iodine at room temperature?

A

Black solid

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5
Q

Why is fluorine an exception to many trends in group 7?

A

F-F bond is unexpectedly weak because the small size of the fluorine atom leads to repulsion between e- because they are so close together

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6
Q

Explain the trend in atomic radius down group 7

A

Increases due to more shells

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7
Q

Explain the trend in electronegativity down group 7

A

Decreases:

  • Atomic radius increases as shielding increases
  • Distance between positive nucleus and negative e- decreases
  • Weaker FoA so less energy required to remove outer e-
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8
Q

Explain the trend in mpt/bpt down group 7

A

Increases:

  • Larger atoms so more e-
  • More vdW forces BtM
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9
Q

Which is more volatile, chlorine or iodine?

A

Chlorine

Lower bpt = more volatile

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10
Q

Which of the first 4 halogens is the best oxidising agent?

A

Fluorine

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11
Q

Which of the first 4 halogens is the best reducing agent?

A

Iodine

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12
Q

Why is iodine a better reducing agent than chlorine?

A

Less electronegative so more likely to give e- away

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13
Q

What happens in a displacement reaction between a halogen and a metal halide in a solution?

A

The halide in the compound will be displaced by a more reactive halogen, but not by a less reactive one

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14
Q

Can chlorine displace a bromide ion?

A

Yes

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15
Q

Can iodine displace a bromide ion?

A

No

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16
Q

What is the equation for the displacement reaction between chlorine and sodium bromide?

A

Cl2 + 2NaBr ——> Br2 + 2NaCl

17
Q

What is the IONIC equation for the displacement reaction between chlorine and sodium bromide?

A

Cl2 + 2Na+ + 2Br- —–> Br2 + 2Na+ + 2Cl-

2Na+ = spectator ion

18
Q

Will bromine displace iodide ions?

A

Yes

19
Q

Will fluroine displace chloride ions?

A

Yes

20
Q

Will chlorine displace iodide ions?

A

yes

21
Q

Will iodine displace bromide ions?

A

No

22
Q

Will chlorine displace fluoride ions?

A

No

23
Q

Does reactivity increase or decrease down group 7?

A

Decreases

24
Q

Do halide ions act as oxidising or reducing agents

A

Reducing

-they lose e- to become halogen molecules

25
Q

What is the equation for the reaction between sodium chloride and sulfuric acid?

What is observed in this reaction?

A

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

NaHSO4 = sodium hydrogen sulfate

Steamy fumes of hydrogen chloride observed

26
Q

What type of reaction occurs between NaCl and H2SO4?

A

Acid-base reaction

(not a reox reaction because no oxidation state has changed since the chloride ion is too weak a reducing agent to reduce sulfur)

27
Q

What is observed in the reaction between a sodium bromide and sulfuric acid?

A

Brown fumes

28
Q

What is observed in the reaction between a sodium iodide and sulfuric acid?

A

Purple fumes

(yellow solid sulfur may also be seen)

29
Q

What are the equations of the 2 reactions that occur when sulfuric acid is added to sodium bromide?

What type of reactions occur?

Are these reactions exothermic or endothermic?

A

NaBr(s) + H2SO4(l) —–> NaHSO4(s) + HBr(g) acid-base reaction

NaBr + H2SO4 —–>Br2 + SO2 redox reaction

Exothermic

30
Q

Why is there an oxidation reaction when sodium bromide/iodide react with sulfuric acid but not when sodium chloride does?

A

Bromide/iodide ions are strong enough reducing agents to reduce the sulphuric acid to sulfur dioxide, but chloride is not

31
Q

What is the name of HClO?

A

Chloric (I) acid

32
Q

What is the equation of the reaction between chlorine and water?

What type of reaction is this?

A

Cl2(g) + H2O(l) <——> HClO(aq) + Hcl(aq)

dissproportionation

33
Q

What is a dissproportionation reaction?

A

Oxidation state of some atoms of the same element increase and others decrease

34
Q

Is chloric (I) acid an oxidising agent or reducing agent?

A

Oxidising

35
Q

What is chloric (I) acid used for?

A
  • Purification of water
  • Swimming pools
  • Bleach

HClO kills bacteria by oxidation

36
Q

Why is chlorine rapidly lost from outdoor pools?

A

In sunlight chlorine reacts with water to form hydrochloric acid (aq) and oxygen

37
Q

Why can chlorine be used in swimming pools despite the fact it is toxic?

A

It is used in very dilute concentrations