(U1) Halogens

Question 1

What colour and state is Fluorine

Answer 1

Yellow gas

Question 2

what colour and state is Chlorine

Answer 2

Yellow-Green gas

Question 3

what colour and state is Bromine

Answer 3

Red-Brown liquid

Question 4

what colour is solid Iodine

Answer 4

Grey-Black

Question 5

what colour is Iodine vapor

Answer 5

Purple

Question 6

what colour is Chlorine water

Answer 6

Pale Green/Colourless

Question 7

what colour is Bromine water

Answer 7

Brown

Question 8

what colour is Iodine in POLAR solvents

Answer 8

Yellow-Brown

Question 9

what colour is Iodine in NON-POLAR Solvents

Answer 9

Purple

Question 10

What is the observation for reactions between:

• Fluorides and
• Concentrated Sulfuric Acid

(Not needed as much)

Answer 10

Steamy/Misty Fumes (of HF)

Question 11

What is the observation for reactions between:

• Chlorides and
• Concentrated Sulfuric Acid

Answer 11

Steamy/Misty Fumes (of HCI)

Question 12

What are the observations for reactions between:

• bromides and
• Concentrated Sulfuric Acid
  (3)

Answer 12

• Steamy/Misty Fumes (HBr)
• Red-Brown Vapour (Br₂)
• pungent smell (SO₂)

Question 13

What are the observations for reactions between:

• Iodides and
• Concentrated Sulfuric Acid
  (7)

Answer 13

4 reactions:

1.

• Steamy/misty fumes (of HI)

2. • Purple Vapour (I₂)
   • pungent smell (SO₂)

• Yellow solid (S)
• Grey-Black solid (I₂)

• Smell of Rotten Eggs (H₂S)
• Grey-Black solid (on the sides of the test tube) (I₂)

Question 14

What is the observation for reactions between:

• solid fluorides and
• Concentrated phosphoric Acid

Answer 14

Steamy/misty fumes (of HF)

Question 15

What is the observation for reactions between:

• Chlorides and
• Concentrated phosphoric Acid

Answer 15

Steamy/misty fumes (of HCI)

Question 16

What is the observation for reactions between:

• Bromides and
• Concentrated phosphoric Acid

Answer 16

Steamy/misty fumes (of HBr)

Question 17

What is the observation for reactions between:

• Iodides and
• Concentrated phosphoric Acid

Answer 17

Steamy/misty fumes (of HI)

Question 18

State every reaction between sodium iodide and sulphuric acid in order

Answer 18

• NaI + H₂SO₄ —> HI + NaHSO₄
• HI + H₂SO₄ —> SO₂ + I₂ + 2H₂O
• 6HI + H₂SO₄ —> S + I₂ + 4H₂O
• 8HI + H₂SO₄ —> H₂S + 4I₂ + 4H₂O

Last 2 reactions occur because iodide ions are greater reducing agents than halides up the group

Question 19

What happens to the oxidising ability of halogens down the group?

Answer 19

Oxidising ability decreases

Question 20

What happens to the reducing ability of halides down the group?

Answer 20

Reducing ability increases

Question 21

Why are halide ions reducing agents while atoms are oxidising agents? (3)

Answer 21

• ions lose electrons more readily
• larger atomic radius + greater shielding make this easier
• also halogen atoms would rather gain electrons than lose (oxidising agents), ions are stable

Question 22

Why are the halogens more soluble in non-aqueous / non polar solvents than in aqueous / polar solvents?

Answer 22

like dissolves like

• halogen molecules and non-polar solvents are both held by Van der Waals forces
• as a result little energy is required to disrupt the forces and form a solution
• aqueous solutions contain Van der Waals, permanent dipole-dipole attractions and hydrogen bonds —> requires more energy to disrupt

Question 23

Why are the halogens soluble in aqueous / polar solvents?

Answer 23

Purely because polar solvents are polar and halogens are non-polar —> opposites attract

Question 24

What colour is Chlorine in non-polar solvents?

Answer 24

Pale green - but not colourless

Question 25

What **colour** is *Bromine* in **non-polar solvents**?

Answer 25

Brown

Question 26

Give the *balanced symbol equation* for the reaction between **water and chlorine** Give **state symbols** Then give the **word equation**

Answer 26

- Cl_{2 (g)} + H₂O_(l) —> HCl_(aq) + HClO_(aq) - chlorine + water —> hydrochloric acid + chloric (I) acid (or chlorine water)

Question 27

Give the *balanced symbol equation* for the reaction between **chlorine** and **cold dilute NaOH** Include **state symbols** Then give the **ionic equation**

Answer 27

- Cl_{2 (g)} + 2NaOH_(aq) —> NaCl_(aq) + NaClO_(aq) + H₂O_(l) - Cl_{2 (g)} + 2OH^-_(aq) —> Cl^-_(aq) + ClO^-_(aq) + H₂O _(l)

Question 28

Give the *balanced symbol equation* for the reaction between **chlorine** and **hot (70ºC) concentrated NaOH** Include **state symbols** Then give the **ionic equation**

Answer 28

- 3Cl_{2 (g)} + 6NaOH_(aq) —> 5NaCl_(aq) + NaClO_{3 (aq)} + 3H₂O_(l) - 3Cl_{2 (g)} + 6OH^-_(aq) —> 5Cl^-_(aq) + ClO₃^-_(aq) + 3H₂O _(l)

Question 29

What does and **Iodate ion (IO^-)** *disproportionate to produce*?

Answer 29

**Iodide (I^-)** and **Iodate (V) (IO₃^-)** ions

Question 30

*Why* is **chlorine** added to **drinking water**?

Answer 30

Kills pathogens and prevents spread of disease

Question 31

*Why* is **ozone** added to **drinking water**?

Answer 31

Breaks down parasites along with pathogens

Question 32

What are the **advantages** and **disadvantages** of using *chlorine in drinking water*? Give **2 of each**.

Answer 32

Advantages: - Chlorine is a highly efficient disinfectant - Residual chlorine remains in the water —> controls contamination - Easy to produce and relatively cheap. - Chlorine gas can be compressed. Disadvantages: - Chlorine is poisonous/toxic. - Can’t treat all water-borne pathogens while ozone can - can react to produce compounds known as disinfection by-products (DBP) which can cause health hazards such as cancer. - volatile and not all of it remains dissolved in the water. - Can spoil the taste of the water. - Chlorine can affect the odour/smell of the water. - Storing large quantities of chlorine causes problems. - inhibits freedom of choice

Question 33

What are the **advantages** and **disadvantages** of using *ozone in drinking water*? Give **2 of each**.

Answer 33

Advantages: - Cost effective - Greater disinfection effectiveness against bacteria and viruses than chlorination. - Has oxidising properties —> lowers the concentration of metals such as iron and manganese by converting them into insoluble metal oxides that can be removed by filtration. - Can treat all water-borne pathogens. Disadvantages: - Unstable —> **no residual protection** (ozone left in the water to control contamination) - does not remove nitrates or chlorides - does not remove hardness from the water - inhibits freedom of choice