2.2.3, 2.2.4, 2.2.5: Group 7

Question 1

Name of group 7

Answer 1

The halogens

Question 2

Group 7 elements exist as …

Answer 2

diatomic molecules

Question 3

Group 7 elements are

Answer 3

non - metals

Question 4

State at room temp of first 4 halogens

Answer 4

F = gas
Cl = gas
Br = liquid
I = solid

Question 5

Group 7 elements form … ions

Answer 5

halide

Question 6

Boiling points trend

Answer 6

increase down the group
as elements have more electrons
increase in vdw. and stronger
greater intermolecular force to break

Question 7

Electronegativity trend

Answer 7

decreases down the group
(as) atomic radius increases
electrons experience less nuclear attraction as further away

Question 8

Main properties that have trends

3

Answer 8

Boiling points
Electronegativity
Silver halide solubility in NH3

Question 9

Silver halide solubility in NH3 trend

Answer 9

All silver halides precipitate out of aqueous solution

when ammonia is added, solubility in it decreased down the group

Question 10

Reactive trends

4

Answer 10

reduction reactions
oxidation reactions
reactions with H2SO4
displacement reactions

Question 11

Reducing power trend

reduction reactions

Answer 11

Increases down the group
F ions aren’t reducing at all
Causes other ions to gain electrons by donating its own

Question 12

Oxidising power trend

oxidation reactions

Answer 12

decreases down the group
F is the most oxidising element as its most electronegative
it gains electrons causing other ions to lose them

Question 13

Reactions with H2SO4

Answer 13

Due to different reducing abilities down the group
HCl or HF
some Br2 and some SO2
I2 immeadiatly reduces S to H2S (toxic smells like eggs)

Question 14

Displacement reactions

why

Answer 14

If an elemental halide is added to a halide solution = the heavier halide is displaced
(as) the lighter halide is more electronegative

Question 15

Reactions with silver nitrate to identify halides

Answer 15

Ag + X > AgX
precipitate formed
AgCl = white
AgBr = cream
AgI = yellow

Question 16

Result if ammonia is added to a silver halide

Answer 16

AgCl precipitate will redissolve
AgBr precipitate will redissolve slowly in presence of lots of NH3
AgI won’t redissolve

Question 17

Disproportionation reaction

Answer 17

An element is oxidised and reduced simultaneously

Question 18

Reaction of chlorine and water

use and equation

Answer 18

used in water treatment to kill bacteria

Cl2 +H2O = HCl + HClO = 2H+ + ClO- + Cl-

Question 19

Reaction of chlorine and water in sunlight

Answer 19

same reaction and further reaction

overall reaction: 2Cl2 + 2H2O = 4HCl + O2

Question 20

Practical uses of chlorine

2

Answer 20

making bleach

adding to the water supply

Question 21

Making bleach with chlorine

Answer 21

disproportionation reaction

Cl2 + 2NaOH > NaClO + H2O + NaCl

Question 22

Adding chlorine to the water supply
benefit
risk

Answer 22

+Kills harmful bacteria

- small increased risk of cancer

Question 23

Chlorine
dangers
3

Answer 23

Cl gas = toxic
Cl liquid = burns eyes and skin
water contains organic trace compounds = chlorine will chlorinate hydrocarbons = carcinogenic