Group 7 - The Halogens

Question 1

what happens to the reactivity down group 7

Answer 1

Decreases as it becomes harder to gain an electron due to increased shielding causing decreasing nuclear attraction

Question 2

What happens to boiling point down group 7

Answer 2

Increases down thevgroup as all are simple covalent structures therefore held together with van der walls forces. Strength increases down the group due to increasing Ar therfore more energy is required to overcome them

Question 3

What happens to oxidising power down group 7

Answer 3

Decreases down the group as their ability to attract electrons decreases (oilrig) due to greater shielding and atomic radius.

Decreasing oxidation power means halogens will displace any halide beneath it

Question 4

Are halides reducing or oxidising agents

Answer 4

Reducing agents as they themselves are oxidised. They donate electrons to other species.

Question 5

What happens to halide reducing power down the group

Answer 5

Increases as electrons are easier to lose due to increased sheilding and decreasing nuclear attraction

Question 6

How do fluorine and chlorine react with H2SO4

Answer 6

NaF + H2SO4 -> NaHSO4 + HF
NaCl + H2SO4 -> NaHSO4 + HCl

Question 7

How to bromide ions react with H2SO4

Answer 7

NaBr + H2SO4 -> NaHSO4 + HBr
2HBr + H2SO4 -> Br2 + SO2 + 2H20

Question 8

How do iodide ions react with H2SO4

Answer 8

NaI + H2SO4 -> NaSO4 + HI
2HI + H2SO4 -> I2 + SO2 + 2H2O
6HI + H2SO4 -> H2S + 3I2 + 2H2O

Question 9

What substance do you add to text for halide ions

Answer 9

Acidified silver nitrate

Question 10

What will happen when you add acidified silver nitrate to a halide

Answer 10

Cl - white precipitate
Br- creme precipitate
I- yellow precipitate

Question 11

How can you test precipitates formed during halide tests

Answer 11

Dilute ammonia will re-dissolve Cl
Conc ammonia will redisdolve Br
I will not redissolve.

Question 12

What happens when chlorine is reacted with water

Answer 12

Chlorine and chlorate ions are formed causing a disproportionation reaction ( cl is both oxidised and reduced)

Cl2 + 2H2O -> ClO3nminus + Cl minus + 2H plus

Question 13

What happens to Cl in the presence of UV light

Answer 13

2Cl2 + 2H20 -> 4HCl + O2
It decomposes

Question 14

How is bleach produced

Answer 14

Cl mixed with cold, aqueous NaOH to produce hypochloride

2NaOH + Cl2 -> NaCIO + NaCl + H2O