4.3 HALOGENS Flashcards

1
Q

What group are the halogens in

A

7

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2
Q

Why does the melting/boiling point of the halogens increase as you go down the group

A
  • The molecules become larger
  • So the intermolecular forces become stronger
  • More energy is needed to overcome these intermolecular forces.
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3
Q

What is special about all the halogens molecular formular

A

They are all diatomic (have a 2 e.g Br2)

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4
Q

What type of structure are the halogens

A

Simple molecular substances, covalently bonded

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5
Q

What happens to the trend of colours of the halogens as you go down the group

A

They get darker as you go down

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6
Q

Formula, colour and state of fluorine

A
  • F2
  • Very Pale Yellow
  • Gas
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7
Q

Formula, colour and state of Chlorine

A
  • C2
  • Pale Green
  • Gas
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8
Q

Formula, colour and state of Bromine

A
  • Br2
  • Orange
  • Liquid
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9
Q

Formula, colour and state of Iodine

A
  • I2
  • Dark Grey
  • Solid
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10
Q

Formula, colour and state of Astatine

A
  • At2
  • Black
  • Solid
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11
Q

What halogen is volatile

A

Bromine

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12
Q

What does iodine do easily

A

Sublime

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13
Q

What fumes does iodine release

A

Purple

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14
Q

What fumes does bromine release

A

Orange

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15
Q

When a halogen reacts with a metal, what compound is formed and how is it a redox reaction

A

An ionic compound. The halogen becomes reduced as it gains an electron, and the metal becomes oxidised as it loses an electron(s)

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16
Q

Define Halide Formation

A

When a halogen reacts with another substance, gains an electron and becomes a negative ion

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17
Q

What are the 3 properties of hydrogen halides

A
  1. Are all gases
  2. Dissolve easily in water
  3. Become strong acids
18
Q

When halogens become halide ions, what happens to the ending of their names

A

It changes to ‘-ide’

For example: Chlorine → Chloride

19
Q

Why do the halogens get less reactive as you go down the periodic table?

A
  • As you go down the table
  • The atoms get larger, so have more electron shells
  • The outer shell of electrons, gets further away from the positive attraction of the nucleus
  • And it’s shielded by more complete electron shells
  • The further the outer shell of electrons is from the positive attraction of the nucleus, the harder it is to attract another electron to complete the outer shell as the attraction is weaker
  • So the reactivity decreases the further you go down the group
20
Q

Chemical test for chlorine

A

Damp blue litmus paper is turns white as it is bleached

21
Q

What is the colour of hydrogen chloride

A

Colourless

22
Q

What type of structure is hydrogen chloride

A

Simple molecular covalent structure

23
Q

What state is hydrogen chloride at room temperature

A

Gas

24
Q

What is dissociation

A

The separating of ions within H2O

25
Q

How does dissociation work with hydrogen chloride

A

When the Halide is bubbled through water, the H+ ions and the CL- ions seperate

26
Q

In water, what does Hydrogen Chloride (g) dissolve into

A

Hydrochloric Acid (Aq)

27
Q

How is HCl(ag) acidic

A

The hydrogen ions dissociate, and the H+ ions present in the solution mean the solution is acidic

28
Q

How come electricity can flow through through hydrochloric acid

A
  • When the hydrogen chloride gas is bubbled through water, it dissociates, and becomes HCl (aq) which is hydrochloric acid.
  • As the HCl(g) has dissociated, there are free ions in the solution that can carry charge and allows electricity to flow
29
Q

What does hydrogen chloride form when dissolved in methlybezene

A

HCl (org) - It doesn’t dissociate

30
Q

Why is HCl(org) in methylbenzene not acidic

A

The H+ ions from the Hydrogen Chloride don’t dissociate, and so there is no source of H+ ions

31
Q

Why can’t HCl(org) in methylbenzene conduct electricity

A

The Hydrogen Chloride doesn’t dissociate, so there are no free ions in the solution to carry charge

32
Q

What is the general equation for a halogen displacement (and give an example)

A

More reactive halogen + less reactive halide salt → less reactive halogen + more reactive halide salt

(Cl2 + KBr → Br2 + KCl)

33
Q

What is the reactivity scale for the halogens, and so what does this mean regarding what halogen can displace the others

A
  1. Fluorine
  2. Chlorine
  3. Bromine
  4. Iodine
  5. Astatine
  • Fluorine is the most reactive so can displace any, followed by chlorine displacing all but fluorine ect.
34
Q

What is the colour of all halide salts

A

Colourless

35
Q

What is the colour of chlorine in an aqueous solution

A

Colourless

36
Q

What is the colour of bromine in an aqueous solution

A

Yellow

37
Q

What is the colour of iodine in an aqueous solution

A

Brown

38
Q

During a halogen displacement reaction, what does the colour change signify and why

A

The more reactive halogen displacing the other, as the halide salts are colourless. The halogen that is not part of the salt, is the new colour in an aqueous solution

39
Q

What type of reaction are all halogen displacements

A

Redox - Something is being reduced, and something is being oxidised

40
Q

In this halogen displacement reaction, what is being oxidised, and what is being reduced and why:

  • Cl2(aq) + 2KBR(aq) → Br2(aq) + 2KCl(aq)
A
  • Chlorine is being reduced as it is gaining an electron (when forming the halide salt)
  • Bromine is being oxidised, as it is losing an electron (when being displaced, it loses the electron it was sharing with hydrogen)