halogens and qualititve analysis

Question 1

f2

Answer 1

pale yellow gas

Question 2

cl2

Answer 2

pale green gas

Question 3

br2

Answer 3

brown orange liquid

Question 4

I2

Answer 4

grey solid

Question 5

boiling point down the group

Answer 5

increases as London forces increase due to an increase size and relative mass of atom
gas at the top of g7 and solids at the bottom

Question 6

electronegativity down. the group

Answer 6

decreases
atom gets larger distance between positive nucleus and bonding electron increases so more shielding

Question 7

displacement reaction
why add hexane

Answer 7

easier to observer colour change

Question 8

halogen present

Answer 8

dissolves readily in organic solvent forming a layer above aqueous layer
coloured band appears

Question 9

reactivity down group 7

Answer 9

decreases as we go down group 7
for a reaction to occur electron is gained
atoms with smaller radius attract electrons Better than larger atoms

halogens less oxidising down g7

Question 10

halide test

Answer 10

silver nitrate then confirm with ammonia solution
testing for cl br i - add dilute nitric acid hno3 then silver nitrate solution agno3
colour of predicate determines Hallie ion

Question 11

iodide

Answer 11

yellow precipate forms
ag= + i- → agi
yellow precipitate insoluble in conc nh3

Question 12

bromide

Answer 12

cream precipate forms
ag= + br- → agbr
further test
add ammonia
cream precipate dissolves in conc nh3

Question 13

chlorine

Answer 13

white percipitate forms
ag+ + cl- → agcl
further test with ammonia
white precipate dissloves in dilute nh3

Question 14

bleach

Answer 14

made via disproportionaton reaction
mix cl and sodium hydroxide = sodium chlorate

Question 15

bleach formula

Answer 15

2naOH (aq) + cl2 (G) → NaCLO(AQ) + NaCl (aq) +h20
cl1 0
cl2 +1
cl3 -1

Question 16

sodium chlorate uses

Answer 16

treating water
bleaching paper and fabrics
cleaning agents

Question 17

water sterilisation

Answer 17

add cl to kill bacteria in water
produce chlorate ions to kill bacteria

Question 18

water sterilisation formula

Answer 18

h20 + cl2 → hcl + HCLO
cl1 0
cl2. -1
cl3 +1

Question 19

chloric acid formula

Answer 19

HCLO+H2- → CLO- +H30+
chloric acid ionises to make chlorate ions

Question 20

advantages of chlorinating water

Answer 20

destroys microorganism that cause disease
long lasting so reduce bacteria build up further down the supply
reduce algae growth that discolours water and gives it a bad taste and smell

Question 21

disadvantages chlorinating drinking water

Answer 21

cl gas toxic irritates respiratory system
liquid cl severe chew burns to skin
cl reacts with organic compounds causing cancer

Question 22

ethical consideration chlorinating water

Answer 22

chlorinating water across uk with no choice
forced medication of population

Question 23

Chlorinating water alternatives

Answer 23

1 ozone powerful oxidising agent kills microorganisms
but short half life non permanent treatment and expensive
2 uv radiation damages dna in microorganisms
infective in cloudy water and doesn’t prevent water contamination further down process

Question 24

test for ammonia compounds

Answer 24

add sodium hydroxide
gently heat
if Naoh present ammonia gas forms
use damp red litmus ammonia dissolves in water and turns litmus blue

Question 25

test 4 hydroxide

Answer 25

they are alkaline turn red litmus blue

Question 26

carbonate test

Answer 26

Hcl acid reacts with carbonates to make co2 gas
when bubbled through limewater it turns cloudy

Question 27

test for sulfates

Answer 27

add hcl acid to remove carbonates
these could precipate out after adding barium chloride giving false result
add barium chloride
white percipate if sulphates insoulable
ba2+ (aq) + so4 2- (aq) → baso4 (s)

Question 28

ion testing order

Answer 28

carbonates
sulfates
hallide