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OCR A level Chemistry > Group 7 > Flashcards

Group 7 Flashcards

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1
Q

What colour is chlorine at RTP?

A

Green

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2
Q

What colour is bromine at RTP?

A

Brown

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3
Q

What colour is iodine at RTP?

A

Grey

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4
Q

What state is chlorine at RTP?

A

Gas

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5
Q

What state is bromine at RTP?

A

Liquid

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6
Q

What state is iodine at RTP?

A

Solid

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7
Q

What is the trend in boiling points down the group?

A

Boiling points increase down the group

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8
Q

Why do boiling points increase down the group? (extended answer)

A
  • further down the group halogen MOLECULES contain more electrons
  • the electron cloud can become more unevenly distributed
  • larger dipoles can be induced in neighbouring molecules
  • attraction between larger dipoles means stronger London forces
  • stronger London forces require more energy to be overcome
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9
Q

Why do boiling points increase down the group? (short answer)

A
  • more electrons
  • stronger London forces
  • more energy required to break the intermolecular forces
  • boiling point increases
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10
Q

Why are Cl-Cl bonds the strongest?

A
  • the covalent bonds are formed by a shared pair of electrons being attracted to the nuclei of the bonded atoms
  • the closer electrons are to the nucleus the stronger the attraction
  • chlorine is the smallest atom
  • smaller atoms have a higher nuclear charge
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11
Q

Why are halide ions larger than their atoms?

A
  • an additional electron has been added
  • this leads to greater repulsion between the electrons
  • meaning ions are smaller
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12
Q

What can be added to a halide solution to test for which halide ion is present?

A

An organic solvent, such as cyclohexane or hexane

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13
Q

When cyclohexane is added to a solution containing chloride ions, what would be seen?

A

Two layers form, the top one pale green

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14
Q

When cyclohexane is added to a solution containing bromide ions, what would be seen?

A

Two layers form, the top one orange

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15
Q

When cyclohexane is added to a solution containing iodide ions, what would be seen?

A

Two layers form, the top one violet

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16
Q

When the mixture of halide solution and hexane is shaken why does the colour of the top layer become more vivid?

A
  • halogens are much more soluble in the organic layer
  • shaking assists the movement of the halogens into the organic layer
  • as their concentration increases, the colour becomes more vivid
17
Q

What is the colour of Cl2 in water?

A

Pale green

18
Q

What is the colour of l2 in water?

A

Brown

19
Q

What is the colour of Br2 in water?

A

Orange

20
Q

Which halogen is the most powerful oxidising agent?

A

Fluorine

21
Q

Which halogen is the least powerful oxidising agent?

A

Astatine

22
Q

What is the trend in reactivity down the group?

A

Reactivity decreases

23
Q

Why does reactivity decrease down the group?

A
  • halogens react by gaining an electron
  • no. shells increases down the group
  • shielding increases
  • atomic radius increases
  • attraction of the nucleus to electrons decreases
24
Q

Does chlorine react with Br-, I-, or both?

A

Both

25
Q

Does bromine react with Cl-, I-, or both?

A

I-

26
Q

Does iodine react with Cl-, Br-, or both?

A

Neither

27
Q

Define disproportionation reaction

A

A redox reaction in which an element is both oxidised and reduced

28
Q

Write the word equation for the reaction between water and chlorine

A

Chlorine + water —> Chloric(I) acid + hydrochloric acid

29
Q

Write the symbol equation for the reaction between water and chlorine

A

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

30
Q

How is the reaction between chlorine and water used?

A

To purify water, the chloric (I) acid produced kills bacteria in drinking water

31
Q

When universal indicator is added to a solution of chlorine in water what colour does it first turn?

A

Red

32
Q

Why does universal indicator first turn red when added to a solution of chlorine in water?

A

The acids in the solution release H+ ions

33
Q

After a while what happens to colour of the indicator in a solution of chlorine in water?

A

Colourless

34
Q

Why does the universal indicator turn colourless after a while of being in a solution of chlorine in water?

A

The ClO- ions bleach the solution

35
Q

Give the word equation for the reaction of chlorine with COLD DILUTE sodium hydroxide

A

Chlorine + Sodium hydroxide —> sodium chorate (I) + sodium chlorine + water

36
Q

Give the symbol equation for the reaction of chlorine with COLD DILUTE sodium hydroxide

A

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

37
Q

What is sodium chlorate (I) used for?

A

A household bleach

38
Q

Why is sodium chlorate (I) a more effective bleach than chloric(I) acid?

A

It is more stable/decomposes less readily and so stays reactive for longer

OCR A level Chemistry (30 decks)

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