group 7

Question 1

what is fluorine like at room temp

Answer 1

pale yellow gas

Question 2

what is chlorine like at room temp

Answer 2

pale green gas

Question 3

what is bromine like at room temp

Answer 3

brown orange liquid

Question 4

what is iodine like at room temp

Answer 4

grey solid

Question 5

bpt trend

Answer 5

increases as we go down group because van der waals forces increase due to increase in size and mass of atoms

Question 6

electronegativity trend

Answer 6

decreases down the group as the atoms get larger and the distance between positive nucleus and bonding electrons increases and there is more shielding

Question 7

reactivity trend

Answer 7

decreases as we go down the group as for a reaction to occur gain electron and smaller atom radius attract electrons better than large atoms

Question 8

halogen are less … as we go down the group

Answer 8

oxidising

Question 9

how is bleach made

Answer 9

via a disproportionation reaction
mixing chlorine and sodium hydroxide will form sodium chlorate (|)

Question 10

why is it called a disproportionation reaction

Answer 10

chlorine has been simultaneously reduced and oxidised

Question 11

uses of sodium chlorate

Answer 11

treating water
bleaching paper and fabrics
cleaning agents

Question 12

adding chlorine to water can …

Answer 12

kill bacteria

Question 13

what happened when chlorine is added to water

Answer 13

produces chlorate ions which kill bacteria and is useful in drinking water and pools
this is a disproportionation reaction

Question 14

… can decompose chlorinated water

Answer 14

sunlight and it can means no ClO- is made so cannot kill bacteria

Question 15

what are advantages of chlorinating drinking water

Answer 15

destroys microorganisms that cause disease
long lasting so reduces bacteria build up further down the supply
reduces growth of algae that discolours water and can give bad taste

Question 16

what are disadvantages of chlorinating drinking water

Answer 16

chlorine gas is toxic and irritate respiratory system
liquid chlorine causes chemical burns to the skin
chlorine can react with organic compound present to make chloroalkanes which have been linked to causing cancer but risk of not chlorinating could lead to cholera epidemic

Question 17

halide ions lose electrons so the are … agents

Answer 17

reducing

Question 18

reducing power trend

Answer 18

down the group ionic radius increases
the distance between nucleus and outer electrons becomes larger and more shielding. attractive force gets weaker
outer electron is lost more readily so lower down group better at reducing

Question 19

tests to prove trend of reducing power

Answer 19

reaction w sulphuric acid- some halide ions can reduce conc sulfuric acid

Question 20

reaction of halides with sulfuric acids

Answer 20

A-makes white misty fumes, produces NaHSO4

B- redox half equations- Br oxidised, S reduced, produces SO2- orange vapour of Br2

C- I- oxidised, sulfur being reduced, produces S- yellow solid of S produced

D- I- ions oxidised, S being reduced produces H2S - rotten egg smell of H2S produced

Cl- A
Br- A+B
I- A+B+C+D

Question 21

reaction of halides with silver nitrate

Answer 21

add dilute nitric acid- to react with any other anions to prevent false results
then silver nitrate solution
Cl- white precipitate
I- yellow precipitate
Br- cream precipitate
further test of ammonia
Cl- dissolves in dilute NH3
Br- dissolves in concentrated NH3
I- insoluble in concentrated NH3