4.3 HALOGENS

Question 1

What group are the halogens in

Answer 1

7

Question 2

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

Answer 2

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

Question 3

What is special about all the halogens molecular formular

Answer 3

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

Question 4

What type of structure are the halogens

Answer 4

Simple molecular substances, covalently bonded

Question 5

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

Answer 5

They get darker as you go down

Question 6

Formula, colour and state of fluorine

Answer 6

• F2
• Very Pale Yellow
• Gas

Question 7

Formula, colour and state of Chlorine

Answer 7

• C2
• Pale Green
• Gas

Question 8

Formula, colour and state of Bromine

Answer 8

• Br2
• Orange
• Liquid

Question 9

Formula, colour and state of Iodine

Answer 9

• I2
• Dark Grey
• Solid

Question 10

Formula, colour and state of Astatine

Answer 10

• At2
• Black
• Solid

Question 11

What halogen is volatile

Answer 11

Bromine

Question 12

What does iodine do easily

Answer 12

Sublime

Question 13

What fumes does iodine release

Answer 13

Purple

Question 14

What fumes does bromine release

Answer 14

Orange

Question 15

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

Answer 15

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

Question 16

Define Halide Formation

Answer 16

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

Question 17

What are the 3 properties of hydrogen halides

Answer 17

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

Question 18

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

Answer 18

It changes to ‘-ide’

For example: Chlorine → Chloride

Question 19

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

Answer 19

• 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

Question 20

Chemical test for chlorine

Answer 20

Damp blue litmus paper is turns white as it is bleached

Question 21

What is the colour of hydrogen chloride

Answer 21

Colourless

Question 22

What type of structure is hydrogen chloride

Answer 22

Simple molecular covalent structure

Question 23

What state is hydrogen chloride at room temperature

Answer 23

Gas

Question 24

What is dissociation

Answer 24

The separating of ions within H2O

Question 25

How does dissociation work with hydrogen chloride

Answer 25

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

Question 26

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

Answer 26

Hydrochloric Acid (Aq)

Question 27

How is HCl(ag) acidic

Answer 27

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

Question 28

How come electricity can flow through through hydrochloric acid

Answer 28

* 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

Question 29

What does hydrogen chloride form when dissolved in methlybezene

Answer 29

HCl (org) - It doesn't dissociate

Question 30

Why is HCl(org) in methylbenzene not acidic

Answer 30

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

Question 31

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

Answer 31

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

Question 32

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

Answer 32

More reactive halogen + less reactive halide salt → less reactive halogen + more reactive halide salt (Cl2 + KBr → Br2 + KCl)

Question 33

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

Answer 33

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.

Question 34

What is the colour of all halide salts

Answer 34

Colourless

Question 35

What is the colour of chlorine in an aqueous solution

Answer 35

Colourless

Question 36

What is the colour of bromine in an aqueous solution

Answer 36

Yellow

Question 37

What is the colour of iodine in an aqueous solution

Answer 37

Brown

Question 38

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

Answer 38

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

Question 39

What type of reaction are all halogen displacements

Answer 39

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

Question 40

In this halogen displacement reaction, what is being oxidised, and what is being reduced and why: * Cl2(aq) + 2KBR(aq) → Br2(aq) + 2KCl(aq)

Answer 40

* 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)