halogens

Question 1

appearance and state F2 at room temp

Answer 1

pale yellow gas
very reactive
toxic

Question 2

appearance and state of Cl2 room temp and pressure

Answer 2

pale green gas
very reactive
toxic

Question 3

appearance and state Br2 room temp and pressure

Answer 3

red/brown liquid
very reactive
toxic

Question 4

appearance and state I2 room temp and pressure

Answer 4

grey/black solid crystal
reactive
toxic

Question 5

trend of atomic radii of halogens

Answer 5

increases down the group

Question 6

trend of electronegativity of halogens

Answer 6

decreases down the group

Question 7

reactivity trend of halogens

Answer 7

decreases down the group

Question 8

colour of Cl dissolved in solution

Answer 8

pale green

Question 9

colour of Br dissolved in solution

Answer 9

orange/brown

Question 10

colour of I dissolved in water

Answer 10

orange/brown

Question 11

colour of I dissolved in cyclohexane

Answer 11

purple

Question 12

distinguishing between bromine and iodine solution (both brown/orange solution)

Answer 12

add cyclohexane and shake
purple layer with iodine
bromine layer remains brown/orange

Question 13

observation adding Fe2+ to Cl

Answer 13

turns pale yellow

Question 14

observation on adding Fe2+ to Br

Answer 14

turns pale yellow

Question 15

observation on adding Fe2+ to I

Answer 15

no reaction

Question 16

Cl2 + 2KBr

Answer 16

2KCl + Br2

Question 17

Cl2 + 2KI

Answer 17

2KCl + I2

Question 18

result of Cl with KBr

Answer 18

Cl more reactive so displaces Br
colourless solution turns orange/brown

Question 19

result of Cl with KI

Answer 19

Cl more reactive so displaces I
colourless solution turns orange/brown
cyclohexane turns purple

Question 20

result of Br with KI

Answer 20

colourless solution turns orange/brown
cyclohexane turns purple

Question 21

what should you add if you have difficulty interpreting results of halide displacement

Answer 21

add cyclohexane
remains orange/brown with bromine
turns purple with iodine

Question 22

how does halogen oxidising ability change down the group

Answer 22

decreases down the group

Question 23

why is Cl the most oxidising

Answer 23

Cl has the fewest electron shells
least shielding
smallest radius
strongest ability to attract electron

Question 24

define disproportionation reaction

Answer 24

simultaneous oxidation and reduction of an atom of the same element in an ion or molecule

Question 25

chlorine plus cold alkali (ClO- stable)

Answer 25

Cl2 + 2NaOH --> NaClO + NaCl + H2O

Question 26

chlorine plus hot alkali (ClO- further reduced)

Answer 26

3Cl2 + 6NaOH --> NaClO3 + 5NaCl + H2O

Question 27

observation of halogens on adding NaOH

Answer 27

turn colourless

Question 28

Cl2 + H2O

Answer 28

HClO + HCl

Question 29

NH3 + HCl

Answer 29

NH4Cl (same for I and Br)

Question 30

what does HCl gas appear as

Answer 30

steamy fumes

Question 31

how does halide reducing ability change down the group

Answer 31

increases

Question 32

why is I- the strongest reducing agent

Answer 32

most electron shells largest radius more shielding outermost electron less strongly attracted to the nucleus

Question 33

method: concentrated H2SO4 with potassium halides

Answer 33

KX + H2SO4 test the gases evolved with conc NH3 on a glass rod, acidified dichromate paper, damp blue litmus paper and bubbling through silver nitrate solution

Question 34

what does acidified dichromate paper test for

Answer 34

SO2

Question 35

what does damp blue litmus paper test for

Answer 35

acidic gas

Question 36

observation on adding HCl to either CO3 2- or HCO3 -

Answer 36

effervescence colourless gas

Question 37

Na2CO3 + HCl —>

Answer 37

NaCl + CO2 + H2O

Question 38

NaHCO3 + HCl —>

Answer 38

NaCl + CO2 + H2O

Question 39

what kind of reaction is Cl- and H2SO4 and why

Answer 39

acid/base not redox because Cl- not a strong enough reducing agent to reduce sulphur

Question 40

acid/base reaction H2SO4 + NaCl

Answer 40

NaHSO4 + HCl

Question 41

acid/base reaction H2SO4 + NaBr

Answer 41

NaHSO4 + HBr

Question 42

what kind of reaction is Br- or I- and H2SO4 and why

Answer 42

redox strong enough reducing agents to reduce sulphur

Question 43

redox reaction H2SO4 + 2Br- + 2H+

Answer 43

SO2 + 2H2O + Br2 (sulphur is reduced bromine is oxidised)

Question 44

what 3 ways can I- reduce S in H2SO4

Answer 44

SO2 S8 H2S

Question 45

method: test for halide ions

Answer 45

1cm3 of halide solution 3 drops dilute nitric acid 5 drops silver nitrate solution add dilute ammonia solution + mix if no change add concentrated ammonia solution

Question 46

AgCl ppt

Answer 46

white

Question 47

AgBr ppt

Answer 47

cream

Question 48

AgI ppt

Answer 48

yellow

Question 49

which ppt is soluble in dilute ammonia solution

Answer 49

AgCl

Question 50

which ppts are soluble in concentrated ammonia solution

Answer 50

AgCl and AgBr

Question 51

is AgI soluble in ammonia solution

Answer 51

no

Question 52

what do you add before AgNO3 to react with carbonate

Answer 52

dilute nitric acid

Question 53

what do you add before AgNO3 to react with sulphate

Answer 53

barium nitrate

Question 54

what is the problem with having carbonate or sulphate ions present for halogen test

Answer 54

Ag+ will form a precipitate with Co3 2- or SO4 2-

Question 55

what does barium nitrate + SO4 2- produce

Answer 55

barium sulphate (white precipitate)