The halogens

Question 1

What is the colour and state of fluorine at room temperature?

Answer 1

Pale yellow gas

Question 2

What is the colour and state of chorine at room temperature?

Answer 2

Pale greenish gas

Question 3

What is the colour and state of bromine at room temperature?

Answer 3

Red/brown liquid

Question 4

What is the colour and state of iodine at room temperature?

Answer 4

Black solid

Question 5

Why is fluorine an exception to many trends in group 7?

Answer 5

F-F bond is unexpectedly weak because the small size of the fluorine atom leads to repulsion between e- because they are so close together

Question 6

Explain the trend in atomic radius down group 7

Answer 6

Increases due to more shells

Question 7

Explain the trend in electronegativity down group 7

Answer 7

Decreases:

• Atomic radius increases as shielding increases
• Distance between positive nucleus and negative e- decreases
• Weaker FoA so less energy required to remove outer e-

Question 8

Explain the trend in mpt/bpt down group 7

Answer 8

Increases:

• Larger atoms so more e-
• More vdW forces BtM

Question 9

Which is more volatile, chlorine or iodine?

Answer 9

Chlorine

Lower bpt = more volatile

Question 10

Which of the first 4 halogens is the best oxidising agent?

Answer 10

Fluorine

Question 11

Which of the first 4 halogens is the best reducing agent?

Answer 11

Iodine

Question 12

Why is iodine a better reducing agent than chlorine?

Answer 12

Less electronegative so more likely to give e- away

Question 13

What happens in a displacement reaction between a halogen and a metal halide in a solution?

Answer 13

The halide in the compound will be displaced by a more reactive halogen, but not by a less reactive one

Question 14

Can chlorine displace a bromide ion?

Answer 14

Yes

Question 15

Can iodine displace a bromide ion?

Answer 15

No

Question 16

What is the equation for the displacement reaction between chlorine and sodium bromide?

Answer 16

Cl₂ + 2NaBr ——> Br₂ + 2NaCl

Question 17

What is the IONIC equation for the displacement reaction between chlorine and sodium bromide?

Answer 17

Cl₂ + 2Na⁺ + 2Br^- —–> Br₂ + 2Na⁺ + 2Cl^-

2Na⁺ = spectator ion

Question 18

Will bromine displace iodide ions?

Answer 18

Yes

Question 19

Will fluroine displace chloride ions?

Answer 19

Yes

Question 20

Will chlorine displace iodide ions?

Answer 20

yes

Question 21

Will iodine displace bromide ions?

Answer 21

No

Question 22

Will chlorine displace fluoride ions?

Answer 22

No

Question 23

Does reactivity increase or decrease down group 7?

Answer 23

Decreases

Question 24

Do halide ions act as oxidising or reducing agents

Answer 24

Reducing

-they lose e- to become halogen molecules

Question 25

What is the equation for the reaction between sodium chloride and sulfuric acid? What is observed in this reaction?

Answer 25

NaCl(s) + H₂SO₄(l) -----\> NaHSO₄(s) + HCl(g) NaHSO₄ = sodium hydrogen sulfate Steamy fumes of hydrogen chloride observed

Question 26

What type of reaction occurs between NaCl and H₂SO₄?

Answer 26

Acid-base reaction (not a reox reaction because no oxidation state has changed since the chloride ion is too weak a reducing agent to reduce sulfur)

Question 27

What is observed in the reaction between a sodium bromide and sulfuric acid?

Answer 27

Brown fumes

Question 28

What is observed in the reaction between a sodium iodide and sulfuric acid?

Answer 28

Purple fumes | (yellow solid sulfur may also be seen)

Question 29

What are the equations of the 2 reactions that occur when sulfuric acid is added to sodium bromide? What type of reactions occur? Are these reactions exothermic or endothermic?

Answer 29

NaBr(s) + H₂SO₄(l) -----\> NaHSO₄(s) + HBr(g) acid-base reaction NaBr + H₂SO₄ -----\>Br₂ + SO₂ redox reaction Exothermic

Question 30

Why is there an oxidation reaction when sodium bromide/iodide react with sulfuric acid but not when sodium chloride does?

Answer 30

Bromide/iodide ions are strong enough reducing agents to reduce the sulphuric acid to sulfur dioxide, but chloride is not

Question 31

What is the name of HClO?

Answer 31

Chloric (I) acid

Question 32

What is the equation of the reaction between chlorine and water? What type of reaction is this?

Answer 32

Cl₂(g) + H₂O(l) \<------\> HClO(aq) + Hcl(aq) dissproportionation

Question 33

What is a dissproportionation reaction?

Answer 33

Oxidation state of some atoms of the same element increase and others decrease

Question 34

Is chloric (I) acid an oxidising agent or reducing agent?

Answer 34

Oxidising

Question 35

What is chloric (I) acid used for?

Answer 35

- Purification of water - Swimming pools - Bleach HClO kills bacteria by oxidation

Question 36

Why is chlorine rapidly lost from outdoor pools?

Answer 36

In sunlight chlorine reacts with water to form hydrochloric acid (aq) and oxygen

Question 37

Why can chlorine be used in swimming pools despite the fact it is toxic?

Answer 37

It is used in very dilute concentrations