3.1.3 Halogens

Question 1

What is the two purposes of chlorine?

Answer 1

Production of bleach
purification of water

Question 2

equation for chlorine + water?

Answer 2

Cl2(aq) + H20(l) — HCLO(aq) + HCL(aq)

Question 3

What is a disproportion reaction?

Answer 3

a reaction in which the same elemant is simultaneously both oxidised and reduced.

Question 4

Benefits and risks of using chlorine to purify drinking water?

Answer 4

Benefits: Kills bacteria
Negatives: toxic - can make more halogenated hydrocarbons, form carcinogens

Question 5

What is the observations when the universal indicator is placed in water for Chlorine + water?

Answer 5

When chlorine is bubbled it will immediately turn red/yellow/orange and after some time it will turn colourless

Question 6

Chemical formula for bleach?

Answer 6

NACLO

Question 7

Systematic name for bleach?

Answer 7

Sodium chlorate(I)

Question 8

How is bleach formed?

Answer 8

Chlorine is reacted with cold dilute aqueous sodium hydroxide or NAOH

Question 9

Equation for how bleach is formed? (Hint: COLD)

Answer 9

CL2(g) + 2NAOH(aq) — NACL(aq) + NACLO(aq) + H20(L)

Question 10

Why does sodium hydroxide solution have to be hot (above 75)

Answer 10

It increases the oxidation number
inc energy

Question 11

Purpose of displacement reaction?

Answer 11

Check reactivity of an element

Question 12

3 Halogens we need to know:

Answer 12

Chlorine
bromine
iodine

Question 13

state and colour at room temp of Chlorine:

Answer 13

Gas
yellow-green

Question 14

state and colour at room temp of Bromine:

Answer 14

orange
liquid

Question 15

state and colour at room temp of Iodine:

Answer 15

Solid
Green

Question 16

Colour of vapour and solution of Chlorine:

Answer 16

Green - v
Green - s

Question 17

Colour of vapour and solution of Bromine:

Answer 17

Orange - V
Orange - S

Question 18

Colour of vapour and solution of Iodine:

Answer 18

Purple - V
Orange/Brown - s

Question 19

Why is cyclohexane added to each test tube?

Answer 19

So its clearer to see top layer as they don’t interact

Question 20

Displacement reaction example equation: chlorine reacting with sodium bromide:

Answer 20

Cl2 + 2NABR – 2NACL + BR2
Chlorine - Halogen
Sodium bromide is the halide

Ionic - CL2 + 2BR- = BR2 + 2CL-

Question 21

What displaces what in a halogen displacement reaction?

Answer 21

More reactive halogen will oxidize and displace the less reactive halide.

Question 22

why cant bromine + sodium chloride not work in a displacement reaction

Answer 22

Chlorine is more reactive then bromine. (less reactive down group 7)

Question 23

How to identify halides?

Answer 23

add silver nitrate which causes a precipitation reaction (insoluble solid)

Question 24

When mentioning precipitates what else must you include?

Answer 24

Colour

Question 25

3 steps to identify halide ions:

Answer 25

1) silver nitrate solution + dilute ammonia = to dissolve chlorine 2) Then add concentrated ammonia = to remove bromine So iodine is left

Question 26

What is the precipitate and colour for Chlorine:

Answer 26

p)AGCL C)white

Question 27

What is the precipitate and colour for Bromine:

Answer 27

P)AGBR C)cream

Question 28

What is the precipitate and colour for Iodine:

Answer 28

P)AGI C)Yellow

Question 29

solubility in dilute ammonia solution solubility in conc ammonia solution Cl

Answer 29

dissolves in both dilute and con

Question 30

solubility in dilute ammonia solution solubility in conc ammonia solution Br

Answer 30

does not dissolves in dilute ammonia solution but does dissolve in conc ammonia solution

Question 31

solubility in dilute ammonia solution solubility in conc ammonia solution I

Answer 31

Does not dissolve in dilute ammonia and does not dissolve in conc ammonia solution