The halogens

Question 1

What are the characteristics and physical properties of the halogens

Answer 1

the most reactive non metals. Do not occur naturally in their elemental form
Exist as stable 1+ ions

Question 2

boiling point trends on group 7

Answer 2

all exist as diatomic molecules, the group contains solids liquids and gasses.

Increases as you go down

Question 3

Displacement reactions with halides

Answer 3

a solution of halogen is added to an aq solution of halides

eg: cl2 + Br- + I-

If the halogen is more reactive than the halide, the halide is displaced and the solution changes colour

Reactions occur when:

Br + Cl (orange colour formation )

I + Cl (violet formation)
I + Br ( violet formation)

Question 4

Trend in reactivity going down the group

Answer 4

Reactivity decreases due to the 3 factors

Question 5

What is disproportionation

Answer 5

A redox reaction in which the same element is both oxidised and reduced

Question 6

Chlorine reaction with water

Answer 6

Used in water purification. When small amounts of water are added to to water, a disproportion reaction occurres

Cl2 + H2O → HClO + HCl

Both products are acids

Question 7

Chlorine + dilute NaOH

Answer 7

The reaction is limited by the low solubility of chlorine in water. If the water contains dissolved NaOH, much more chlorine dissolves

Question 8

Risks and benefits of the use of chlorine in drinking water

Answer 8

Water kills bacteria in water therefore making it safer to drink by reducing the spread of waterborn disease

But chlorine can react with organic compounds in water and form carsenogens which → :(

Question 9

Tests for halides

Answer 9

Aqueous silver nitrate forms:

Cl → white ppt
Br → Cream ppt
I → yellow ppt