Group 7

Question 1

State the trend in

BP for elements in group 7

Answer 1

• Inc
• More e^- shells
• Stronger VDW

Question 2

State the trend in

electronegativity for elements in group 7

Answer 2

• Dec
• Larger atoms attract less e^-
• bc e^- further from nucleus
• Shielding by more e^-

Question 3

When will a halogen displace a halide from a solution?

Answer 3

Halide is below it on periodic table

Question 4

What is the ionic equation when a halogen replaces a halide?

Answer 4

Ho_{2 (aq)} + 2Hi^- _(aq) → 2Ho^- _(aq) + Hi₂ (aq)

Question 5

Give an observation for the reaction btw

chlorine/bromine + iodide

Answer 5

Brown sol (I₂)

Question 6

Give an observation for the reaction btw

chlorine + bromide

Answer 6

Orange sol (Br₂)

Question 7

What happens when you mix chlorine gas w/ cold, dilute, aqueous sodium hydroxide?

What is it used for?

Answer 7

Sodium chlorate (I) sol - NaClO

Bleach - water treatment

Question 8

Outline why chlorine is used in water treatment

Answer 8

• Health benefits outweigh risks
• Used in dilute conc

Question 9

State the trend in

reducing power of halides down the group

Answer 9

• Inc
• Attraction btw nucleus + outer e^- dec
• Ion gets bigger so e^- further away from nucleus
• Shielding

Question 10

What is the test for halides?

Answer 10

• Add dilute nitric acid (remove ions that may interfere)
• Add silver nitrate sol
• Cl^- white ppt
• Br^- cream ppt
• I^- yellow ppt