Halogens

Question 1

What are fluorine chlorine bromine and iodine at room temperature?

Answer 1

Fluorine-gas
Chlorine-gas
Bromine-liquid
Iodine-solid

Question 2

What is the formulae for halogens?

Answer 2

They all tend to exist as diatomic molecules

Question 3

What is the trend in electronegativity down group 7 and why?

Answer 3

It decreases

• atomic radius increases so electrons experience less attraction to the nucleus
• electron shielding also increases
• electrons are further away so are less attracted

Question 4

What is the trend in boiling points down group 7 and why?

Answer 4

Boiling points increase

• because elements have more electrons as you go down the group
• this causes an increase in London dispersion forces
• stronger London dispersion forces means greater intermolecular forces

Question 5

What is the trend of silver halide solubility in ammonia down group 7?

Answer 5

Solubility decreases as you go down group 7

Question 6

What is the trend in reactivity down group 7 and why?

Answer 6

Decreases due to factors such as electronegativity

Question 7

How are halide ions formed in terms of their orbitals?

Answer 7

Halogen goes from an oxidation state of 0 to a halide ion with charge +1 , becomes reduced
This is done through the addition of one electron to the p subshell in order to complete the outer shell

Question 8

What is chlorine sanitation?

What type of reaction is this and why?

Answer 8

Chlorine is used to treat water supplies as it is effective in killing bacteria and prevent the spread of waterborne diseases

Disproportionation reaction: chlorine becomes both reduced and oxidised
Cl + H2O -> HClO + HCl

Question 9

How is household bleach formed?

What type of reaction is this?

Answer 9

When dilute sodium hydroxide and chlorine react together

Disproportionation reaction: chlorine becomes both reduced and oxidised

Question 10

How will chlorine appear in
A)water?
B)cyclohexane?

Answer 10

A)pale green

B)pale green

Question 11

How will bromine appear in
A)water?
B)cyclohexane?

Answer 11

A)orange

B)orange

Question 12

How will Iodine appear in
A)water?
B)cyclohexane?

Answer 12

A)brown

B)violet

Question 13

How can you test for halide ions?

Answer 13

Dissolve suspected halide in water, add an aqueous solution of silver nitrate, colour of precipitate formed...
Silver chloride: white
Silver bromide: cream
Silver iodide: yellow 
Add aqueous ammonia if results are unclear
AgCl-dissolve in dilute
AgBr-dissolve in concentrated
AgI-won’t dissolve