3.1.3 halogens

Question 1

Fluorine

Answer 1

Very pale yellow gas

Highly reactive

Question 2

Chlorine

Answer 2

Greenish, reactive gas, poisonous in high concentrations

Question 3

Bromine

Answer 3

Red liquid, gives off dense brown/orange poisonous fumes

Question 4

Iodine

Answer 4

Shiny grey solid sublimes to purple gas

Question 5

Trend in melting points

Answer 5

Increases down group

Molecules become larger, more electrons so more induced dipole-dipole forces between molecules

As intermolecular forces get larger more energy has to be used to break these

Question 6

Reactivity

Answer 6

Decreases down the group as atoms get bigger with more shielding so they less easily attract and accept electrons

Form -1 ions less easily down the group

Question 7

Chlorine + potassium chloride

Answer 7

Very pale green solution

No reaction

Question 8

Chlorine + potassium bromide

Answer 8

Yellow solution

Cl displaced by Br

Question 9

Chlorine + potassium iodide

Answer 9

Brown solution

Cl has displaced I

Question 10

Bromine + potassium chloride

Answer 10

Yellow solution

No reaction

Question 11

Bromine + potassium bromide

Answer 11

Yellow solution no reaction

Question 12

Bromine + potassium iodide

Answer 12

Brown solution

Br has displaced I

Question 13

Iodine + potassium chloride/bromide/iodide

Answer 13

Brown solution

No reaction

Question 14

Chlorine + potassium chloride if organic solvent is added

Answer 14

Colourless

No reaction

Question 15

Chlorine + potassium bromide if organic solvent is added

Answer 15

Yellow,

Cl has displaced bromide

Question 16

Chlorine + potassium iodide if organic solvent is added

Answer 16

Purple

Cl has displaced I

Question 17

Bromine + potassium chloride if organic solvent is added

Answer 17

Yellow no reaction

Question 18

Bromine + potassium bromide if organic solvent is added

Answer 18

Yellow

No reaction

Question 19

Bromine + potassium iodide if organic solvent is added

Answer 19

Purple

Br has displaced I

Question 20

Iodine + potassium chloride/bromide/iodide if organic solvent is added

Answer 20

Purple

No reaction

Question 21

Disproportionation

Answer 21

Where an element is simultaneously oxidised and reduced

Question 22

Chlorine

Answer 22

Used in water treatment to kill bacteria

Toxic + possible formation of chlorinated hydrocarbons

Question 23

Bleach

Answer 23

Mixture of NaCl and NaClO

Disinfectant, kills bacteria

Question 24

Identifying halides

Answer 24

Test solution is made acidic with nitric acid, then silver nitrate is added

Fluorides - no precipitate

Chlorides - white precipitate

Bromides - cream precipitate

Iodides - pale yellow precipitate

Question 25

If halide colours look similar

Answer 25

Treated with ammonia solution

Silver chloride dissolves in dilute ammonia to form complex ion - [Ag(NH3)2] + Cl- colourless

Silver bromide - dissolves in concentrated ammonia to form complex ion [Ag(NH3)2] + Br- colourless

Silver iodide doesnt react with NH3 - too insoluble

Question 26

Role of nitric acid

Answer 26

React with any carbonates to prevent formation of Ag2CO3

Would mask desired observations