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A-level Chem > Group 7 > Flashcards

Group 7 Flashcards

1
Q

Physical state of Fluorine and Chlorine

A

Gases at RTP.

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2
Q

Physical state of Bromine

A

Liquid at RTP.

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3
Q

Physical state of iodine

A

Solid at RTP.

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4
Q

The mpt and bpt increases down the group, because:

A
  1. Number of electrons increase, so greater uneven electron distribution.
  2. Stronger induced dipole-dipole attractions between molecules.
  3. So, more energy is required to break the attractions between molecules.
  4. Hence, boiling and melting point increases.
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5
Q

Definition of volatility

A

The ease at which a liquid turns into a gas.

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6
Q

Volatility decreases down the group, because:

A
  1. An increase in the number of electrons.
  2. Increases the uneven distribution of electrons.
  3. Stronger induced diploe-dipole forces.
  4. Hence, the volatility decreases.
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7
Q

Reactivity decreases down a group, because:

A
  1. Down the group, the atoms have more electron shells.
  2. More shielding of nuclear charge.
  3. Less nuclear attraction for incoming electrons.
  4. Electrons gained by chlorine more easily than by iodine.
    This means that chlorine has a greater electron affinity for electrons than bromine or iodine.
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8
Q

Defintion of electron affinity

A

Ability of an element to gain an electron.

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9
Q

Definition of oxidising power

A

This is the ability of an atom or species to oxidise another species (take an electron from it).

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10
Q

Halide ion sin solution are…

A

colourless.

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11
Q

Chlorine colour in water…

A

Pale green

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12
Q

Chlorine colour in cyclohexane…

A

Pale green

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13
Q

Bromine colour in water…

A

Orange

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14
Q

Bromine colour in cyclohexane…

A

Orange

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15
Q

Iodine colour in water…

A

Brown

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16
Q

Iodine colour in cyclohexane…

A

Purple

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17
Q

Ionic equ, full equ and obs between chlorine and bromine

A

Cl2(g) + 2Br-(aq) …. Br2(l) + 2Cl-(aq)
Cl2(g) + 2NaBr(aq) …. Br2(l) + 2NaCl(aq)
Obs: pale green to orange (aq or cyclohexane).

18
Q

Ionic equ, full equ and obs between chlorine and iodine

A

Cl2(g) + 2I-(aq) …. I2(s) + 2Cl-(aq)
Cl2(g) + 2NaI(aq) …. I2(s) + 2NaCl(aq)
Obs: Pale green to brown (water) OR orange to purple (cyclohexane).

19
Q

Ionic equ, full equ and obs between bromide and iodine

A

Br2(l) + 2I-(aq) …. 2Br(l) + I2(s)
Br2(l) + 2NaI(aq) …. 2NaBr(aq) + I2(s)
Obs: orange to brown (water) OR orange to purple (cyclohexane).

20
Q

The more reactive halogen takes electrons from the less reactive halide (oxidises it). This is because:

A

Chlorine has less electron shells than Br-/I-.
Chlorine has less sheilding.
Chlorine has more nuclear attraction for incoming electrons.
Chlorine takes electrons from Br-/I-.

21
Q

To prove the reactivity trend, use…

A
  1. Cl2 + Br-
  2. Br2 + I-
22
Q

Obs for chloride and acidified silver nitrate…

A

White precipitate

23
Q

Equ for chloride and acidificed silver nitrate…

A

Ag+(aq) + Cl-(aq) …. AgCl(s)

24
Q

Obs for bromide and acidified silver nitrate…

A

Cream precipitate

25
Q

Equ for bromide and acidified silver nitrate

A

Ag+(aq) + Br-(aq) …. AgBr(s)

26
Q

Obs between iodide and acidified silver nitrate

A

Yellow precipitate

27
Q

Equ between iodide and acidified silver nitrate

A

Ag+(aq) + I-(aq) …. AgI(s)

28
Q

Chloride and dilute ammonia solution

A

AgCl(s) dissolves

29
Q

Bromide and dilute ammonia solution

A

AgBr(s) remains

30
Q

Bromide and concentrated ammonia solution

A

AgBr(s) dissolves

31
Q

Iodide and dilute ammonia solution

A

AgI(s) remains

32
Q

Iodide and concentrated ammonia solution

A

AgI(s) remains (turns white)

33
Q

Silver fluoride and water

A

No precipitate formed as silver fluroride is soluble in water

34
Q

Chlorine and water equ

A

Cl2(g) + H2O(l) ….HClO(aq) + HCl(aq)

35
Q

Explain the change in oxidation numbers for the chlorine and water equ

A

Chlorine is oxidised as the oxidation number increases from 0 in Cl2 to +1 in HClO.
Chlorine is reduced as the oxidation number decreases from 1 in Cl2 to -1 in HCl, so this is reduction.
This is an example of a disproportionation reaction.

36
Q

Definition of disproportionation reaction

A

The same element is both oxidised and reduced.

37
Q

Use for the reaction between water and chlorine

A

Used to kill bacteria in water. The HClO forms reactive oxygen atoms that destroy bacteria in the water.

38
Q

Chlorine and dliute NaOH(aq) equ

A

Cl2(g) + 2NaOH(aq) …. NaClO + NaCl(aq) + H2O(l)

39
Q

Explain the change in oxidation numbers for chlorine and dilute NaOH(aq) equ

A

Chlorine increases in oxidation number from 0 in Cl2 to +1 in NaClO, so chlorine has been oxidised.
Chlorine has decreased in oxidation number from 0 in Cl2 to -1 in NaClO, so chlorine has been reduced.

40
Q

Use for the reaction between chlorine and dilute NaOH(aq)

A

Used in the production of bleach. The active ingredient is NaClO(aq); sodium chlorate (I).

A-level Chem (30 decks)

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