3.1.3 Halogens

Question 1

How does the boiling points change down the group

Answer 1

INCREASE
Stronger induced dipole - dipole forces as increasing size and relative mass

Question 2

Explain why reactivity decreases down the group

Answer 2

Increase atomic radius
Increase electron shielding so atoms ability to gain an outer electron decreases as find it harder to attract an electron

Question 3

What is the colour change when chlorine water is mixed with a potassium chloride solution

Answer 3

Aq = Colourless
Or = Colourless
No reaction

Question 4

What is the colour change when chlorine water is mixed with a potassium bromide solution

Answer 4

Aq = Yellow
Or = Orange
Reaction

Question 5

What is the colour change when chlorine water is mixed with a potassium iodide solution

Answer 5

Aq = Brown
Or = Purple
Reaction

Question 6

What is the colour change when bromine water is mixed with a potassium chloride solution

Answer 6

Aq = Yellow
Or = Orange
No reaction

Question 7

What is the colour change when bromine water is mixed with a potassium bromine solution

Answer 7

Aq = Yellow
Or = Orange
No reaction

Question 8

What is the colour change when bromine water is mixed with a potassium iodide solution

Answer 8

Aq = Brown
Or = Purple
Reaction

Question 9

What is the colour change when iodine water is mixed with a potassium iodide solution

Answer 9

Aq = Brown
Or = Purple
No reaction

Question 10

What is the colour change when iodine water is mixed with a potassium chloride solution

Answer 10

Aq = Brown
Or = Purple
No reaction

Question 11

What is the colour change when iodine water is mixed with a potassium chloride solution

Answer 11

Aq = Brown
Or = Purple
No reaction

Question 12

Define disproportionation

Answer 12

Oxidation and reduction of the same element

Question 13

Explain the characteristic reaction when you add halogens to aqueous ammonia

Answer 13

Chlorine : White precipitate dissolves in dilute ammonia
Bromine : Cream Precipitate dissolves in concerted ammonia
Iodine : Yellow precipitate doesn’t dissolve = insoluble

Question 14

Bromine is used to extract iodine from a solution containing iodine ions

Answer 14

Br2 + 2I– > I2 + 2Br–

Question 15

Explain why iodine is less reactive than bromine

Answer 15

Iodine has a larger atomic radius
Iodine has greater shielding
Iodine has weaker / less nuclear attraction (on electron
gained than bromine

Question 16

Chlorine is used to purify water on a large scale. State the disadvantages of using chlorine for water purification

Answer 16

Chlorine is toxic/poisonous
OR
forms halogenated hydrocarbons
OR
forms carcinogens/toxic compounds

Question 17

Write the systematic name for NaBrO3.

Answer 17

Sodium Bromate (V)

Question 18

Bromine disproportionates when it reacts with potassium hydroxide solution.
Suggest an equation for this reaction

Answer 18

Br2 + 2KOH → KBr + KBrO + H2O