ES1: Halogens

Question 1

What group are the halogens in?

Answer 1

Group 7

Question 2

What block are the halogens in?

Answer 2

P block

Question 3

What electronic configuration do all the halogens have?

Answer 3

ns2np5

Question 4

Why are halogens not found as elements on their own?

Answer 4

Too reactive

Question 5

What three ways do halogens exist naturally?

Answer 5

• Exist as ionic compounds
• Exist as separate covalently bonded diatomic molecules
• By sharing an electron from another metal atom

Question 6

What’s fluorine’s appearance at room temperature?

Answer 6

Pale yellow gas

Question 7

What’s chlorine’s appearance at room temperature?

Answer 7

Green gas

Question 8

What’s bromine’s appearance at room temperature?

Answer 8

Dark red liquid

Question 9

What’s iodine’s appearance at room temperature?

Answer 9

Shiny grey/black solid

Question 10

What’s chlorine’s appearance in water?

Answer 10

Virtually colourless

Question 11

What’s bromine’s appearance in water?

Answer 11

Yellow/orange

Question 12

What’s iodine’s appearance in water?

Answer 12

Brown

Question 13

What’s chlorine’s appearance in hexane?

Answer 13

Virtually colourless

Question 14

What’s bromine’s appearance in hexane?

Answer 14

Orange/red

Question 15

What’s iodine’s appearance in hexane?

Answer 15

Pink/violet

Question 16

How does the reducing ability of the halogens change down the group?

Answer 16

Increases

Question 17

How does the oxidising ability of the halogens change down the group?

Answer 17

Decreases

Question 18

Why does the reducing ability of the halogens increase down the group?(4)

Answer 18

• Increased atomic radius
• Increased electron shells between the nucleus and the outer shell of electrons
• More electron shielding means less of an attraction between the nucleus and the outer shell
• Harder to attract an electron towards it

Question 19

How does the volatility of the halogens change down the group?

Answer 19

Decreases

Question 20

What is volatility?

Answer 20

The ease with which an element evaporates into a gas

Question 21

Why does the volatility of the halogens decrease down the group? (4)

Answer 21

• Increased atomic radius: larger molecule
• Larger electron cloud
• Stronger instantaneous dipole-induced dipole bonds
• Harder to break these strong intermolecular bonds to change state into a gas

Question 22

How does the electronegativity of the halogens change down the group?

Answer 22

Decreases

Question 23

How soluble are halogens in water?

Answer 23

Low solubility

Question 24

Why do halogens have a low solubility in water?

Answer 24

They form covalent and non polar molecules

Question 25

What substances do halogens dissolve more easily in than water?

Answer 25

Organic solvents e.g hexane

Question 26

Why is it useful to dissolve halogens in hexane?

Answer 26

They have more distinctive colours when dissolved in hexane so are easier to tell apart

Question 27

How do halogens react?

Answer 27

By gaining an electron (being reduced) and oxidising another substance

Question 28

Are halogens stronger oxidising agents or reducing agents?

Answer 28

Oxidising agents

Question 29

What is the general formula for a halogen reacting?

Answer 29

X + e- ===> X-

Question 30

What happens in a displacement reaction with halogens?

Answer 30

A more reactive halogen will displace a less reactive halide in a solution

Question 31

Give the formula for a displacement reaction with chlorine and potassium iodide.

Answer 31

Cl2 (aq) + 2KI(aq) ====> 2KCl (aq) + I2 (aq)

Question 32

What colour change would you observe in a displacement reaction with chlorine and potassium iodide?

Answer 32

The solution would turn from pale green to brown

Question 33

How could a clearer colour change be observed in a displacement reaction?

Answer 33

By shaking the solution with hexane

Question 34

What does chlorine do in a displacement reaction with chlorine and potassium iodide? Give the half equation.

Answer 34

- Chlorine displaces iodine and gets reduced | - Cl2 + 2e- ====> 2Cl-

Question 35

What does iodine do in a displacement reaction with chlorine and potassium iodide? Give the half equation.

Answer 35

- Iodine is displaced by chlorine and gets oxidised | - 2I-====> I2 + 2e-

Question 36

How do you write an ionic equation?

Answer 36

Cancel out the unchanged ions

Question 37

What reacts with halide ions to form a precipitate?

Answer 37

Silver ions

Question 38

Give the general formula of a precipitation reaction with silver ions and halide ions.

Answer 38

Ag+ (aq) + X- (aq) ====> AgX(s)

Question 39

How do you test for halides? (2)

Answer 39

- Add dilute nitric acid | - Add silver nitrate solution

Question 40

Why do you add dilute nitric acid when testing for halides?

Answer 40

To remove other ions that could interfere in the reaction

Question 41

What colour precipitate forms with fluorine after reacting with silver ions?

Answer 41

No precipitate forms (trick question :-P)

Question 42

What colour precipitate forms with chlorine after reacting with silver ions?

Answer 42

White

Question 43

What colour precipitate forms with bromine after reacting with silver ions?

Answer 43

Cream

Question 44

What colour precipitate forms with iodine after reacting with silver ions?

Answer 44

Yellow

Question 45

How do you further distinguish between the silver halides?

Answer 45

By adding ammonia solutions of different concentrations

Question 46

What happens when you add ammonia solution to AgCl?

Answer 46

Dissolves in dilute ammonia solution to form a colourless solution

Question 47

What happens when you add ammonia solution to AgBr? (2)

Answer 47

- Does not dissolve in dilute ammonia solution | - Dissolves in concentrated ammonia solution to form a colourless solution

Question 48

What happens when you add ammonia solution to AgI?

Answer 48

Never dissolves