Group 7, the halogens

Question 1

describe the physical appearance of the halogens
chlorine
bromine
iodine

Answer 1

chlorine -yellow green gas
bromine - dark red
iodine - dark grey solid

Question 2

why do not we study fluorine and astatine in the lab ?
F
At

Answer 2

F - too dangerous
At - highly radioactive

Question 3

what is the uses of fluorine ?

Answer 3

manufacture of a wide range of compounds consisting of only carbon and fluorine

Question 4

what is the uses of chlorine ?

Answer 4

production of polymers such as PVC
it kills bacteria

Question 5

what is the uses of bromine ?

Answer 5

a range of products including flame retardants, medicines and dyes

Question 6

what is the uses of iodine ?

Answer 6

used to make products like medicines, dyes and catalysts

Question 7

write the balanced symbol equation for the reaction between magnesium and bromine

Answer 7

Mg (s) + Br2 (aq) -> MgBr2 (g)
- magnesium is oxidized
- bromine is reduced

Question 8

write the ionic equation for the oxidation of iron(II) ions in solution to iron(III) ions by aqueous chlorine

Answer 8

2Fe2+ (aq) + CI2 (aq) -> 2Fe3+ (aq) + 2CI- (aq)

Question 9

why cant iodine iron(II) ions compounds ?

Answer 9

only capable of oxidizing iron to the +2 oxidation state

Question 10

reactions with non metals
- when heated with hydrogen
chlorine
bromines
iodine

Answer 10

chlorine - colorless acidic gas
bromine - pale blueish flame
iodine - reversible reaction

Question 11

what is the test for halide ions

Answer 11

1. place potassium chloride to a height of 1cm into a test tube
2. add silver nitrate until precipitate forms
3. add twice the volume of dilute ammonia, stopper and shake
4. if the precipitate remains, add conc. ammonia in the fume cupboard and shake carefully
5. repeat with potassium bromide and potassium iodide

Question 12

colour of the precipitate with AgNO3
chloride
bromide
iodide

Answer 12

chloride - white
bromide - cream
iodide - yellow

Question 13

solubility of these in dilute ammonia
chloride
bromide
iodide

Answer 13

chloride - ppt dissolves
bromide - ppt remains
iodide - ppts remains

Question 14

solubility in conc. ammonia
chloride
bromide
iodide

Answer 14

chloride - ppt dissolves
bromide - ppt dissolves
iodide - ppt remains

Question 15

halogen displacement reactions method

Answer 15

1. put 1cm3 of metal chloride into 2 test tubes label CI-
2. put 1cm3 of metal bromide into 2 test tubes label Br-
3. put 1cm3 of metal iodide into 2 test tubes label I-
4. put 1cm3 of chloride water into one Br- tube and one I- tube
5. put 1cm3 of bromide water into one CI- tube and one I- tube
6. put 1cm3 of iodide solution into one CI- tube and one Br- tube
7. add 1cm3 of cyclohexane into every test tube. stopper the tube as soon as it is added and shake
8. record the colour in both layers on results table

Question 16

colour of halogen dissolved in water
chlorine
bromine
iodine

Answer 16

chlorine - pale green
bromine - pale yellow
iodine - pale brown

Question 17

colour of aqueous solution
chlorine
bromine
iodine

Answer 17

chlorine - colourless
bromine - colourless
iodine - colourless

Question 18

colour of halogen dissolved in cyclohexane
chlorine
bromine
iodine

Answer 18

chlorine - pale green
bromine - orange
iodine - purple

Question 19

if CI2 is the strongest oxidising agent what is CI- ion

Answer 19

the weakest reducing agent

Question 20

if I2 is the weakest oxidising agent than what is I- ion

Answer 20

the strongest reducing agent

Question 21

state the observations and products of NaCI + conc. H2SO4

Answer 21

-colourless acidic gas forms that fumes in moist air (HCI)
-white solid remains (NaHSO4)

Question 22

what type of reaction is NaCI + conc. H2SO4

Answer 22

acid base reaction so no redox

Question 23

state the observations and products of NaBr + conc. H2SO4

Answer 23

-orange vapour (SO2) mixed with colourless acidic gas
-solid product is NaHSO4
-some HBr is formed

Question 24

what type of reaction is NaBr + conc. H2SO4

Answer 24

redox reaction
- the bromide ions is oxidised to bromine and the sulphur is reduced from +6 to +4
- acid base reaction
-HBr forms

Question 25

state the observations and products of NaI + conc. H2SO4

Answer 25

• a dark solid forms which gives off a purple vapour on warming O2
• some yellow solid may be seen and there is a bad egg smell

Question 26

what type of reaction is NaI + conc. H2SO4

Answer 26

redox reaction
- iodide ions are oxidised to iodine and the sulphur is reduced from +6 to 0 -2

Question 27

oxidising power - define

Answer 27

a measure of the strength with which an atom is able to attract and capture an electron

Question 28

reducing power - define

Answer 28

a measure of the tendency of an atom or ion to donate an electron

Question 29

list three properties the hydrogen halides have in common

Answer 29

• strong acids so ionise completely
• very soluble in water
• colourless gases at room temperature which fume in moist air

Question 30

write the balanced symbol equation for the reaction between ammonia and hydrogen chloride gas

Answer 30

NH3 (g) + HCI (aq) -> NH4CI (s)
- would would see white smoke

Question 31

what is an oxo anion ?

Answer 31

anion with the general formula of X x Oy 2-

Question 32

making bleach

Answer 32

CI2 (g) + 2OH (aq) -> CIO- (aq)+ CI- (aq) + H2O (l)