Group 7 halogens

Question 1

Trend of electronegativity in group 7 and why

Answer 1

Decreases
The number of principal energy levels increase
Weaker attraction between nucleus and electrons in a covalent bond

Question 2

Trend in boiling point
and why

Answer 2

Increases
Size of atom increases. There are more vdw forces between the molecules that need to be broken

Question 3

Appearance at room temperature of the halogens

Answer 3

F2 - Pale yellow gas
Cl2 - Pale green gas
Br2 - Dark red/orange liquid
I2 - Dark purple/black solid

Question 4

Which Halide ion forms a brown solution with Cl2 and Br2

Answer 4

Iodide ion
(KI)

Question 5

Which reaction produces a yellow solution
Give equation(s)

Answer 5

Cl2 + 2Br- ion
Cl2 + 2Br- —-> Br2 + 2Cl-

Question 7

Trend of ability of halide ion to act as a reducing agent

Answer 7

Size of halide ion increase(greater shielding)
Outer electron further away from nucleus
Less attraction between nucleus and outer electrons
Ion therefore able to lose an electron more readily

Question 8

Trend of halogen atoms to act as oxidising agents

Answer 8

As you go down the group the ability for a halogen to act as a oxidising agent decreases
This is because the atomic radius increases hence shielding increases
Hence atom gains an electron less easily as there is less attraction between outer electron and nucleus

Question 9

In the reaction between sodium halide and sulfuric acid which halides cannot oxidise the acid
and name the observations

Answer 9

Fluoride and chloride ions as they are not strong enough and hence will undergo acid base reactions
HF- misty fumes
HCl-misty fumes

Question 10

Reaction of sodium bromide and sulfuric acid observation

Answer 10

HBr- misty fumes does not oxidise

Question 11

Reaction of HBr and sulfuric acid

Answer 11

oxidises sulfuric acid to SO2 choking gas
H2SO4 + 2H+ +2e- —-> SO2 + 2H2O
2Br- ——> Br2 +2e-

H2SO4 + 2H+ +2Br- ——-> Br2 + SO2 + 2H2O

Br2 brown gas

Question 12

What can iodine reduce H2SO4 to

Answer 12

S, SO2, and H2S

Question 13

Acid base reaction of Sodium iodine and sulfuric acid and observation

Answer 13

H2SO4 + 2NaI —-> Na2SO4 + 2HI
misty fumes

Question 14

Iodine ions reducing sulfuric acid to SO2 equations and observations

Answer 14

H2SO4 + 2H+ +2e- ——> SO2 + 2H2O
2I- —-> 2e- + I2
H2SO4 + 2H+ +2I- ——-> SO2 + 2H2O + I2

I2 Black solid/purple gas
S SO2 choking gas

Question 15

Iodine ions reducing sulfuric acid to S equations and observations

Answer 15

6e- + 6H+ + H2SO4 ——> S + 4H2O
2I- —-> I2 + 2e- (x3)
6H+ + H2SO4 + 2I- ——-> S + 4H2O + 6I2
S - yellow solid
I2 - purple gas/black solid

Question 16

Redox reactions of Iodine ions and sulfuric acid equations and observations

Answer 16

8H+ + 8e- + H2SO4 ——> H2S + 4H2O
2I- ——> I2 + 2e- (x4)
8H+ +H2SO4 +8I- ——> H2S + 4H2O + 8I2
H2S - Smell of rotten eggs
I2 - Black solid/purple gas

Question 17

Observation of halide ions with Silver

Answer 17

AgF - No visible change(soluble)
AgCl - White ppt
AgBr - Cream ppt
AgI - Yellow ppt

Question 18

Solubility of Silver halides in dilute ammonia

Answer 18

AgF - X
AgCl - Soluble
AgBr - Sparingly soluble
AgI - Insoluble

Question 19

Solubility of silver halides in concentrated ammonia

Answer 19

AgF - X
AgCl - X
AgBr - Soluble
AgI - Insoluble

Question 20

Equation to show solubility of AgCl or AgBr

Answer 20

AgCl(s) + 2NH3 ——> Ag(NH3)2+ + Cl-
AgBr(s) +2NH3 ——> Ag(NH3)2+ + Br-

Question 21

What happens when chlorine dissolves in water and name the
Equation

Answer 21

Hydrochloric acid and chloric acid forms
Cl2 + H2O ⇌ HCl + HClO

Question 22

Redox reaction of water and chlorine in bright sun light

Answer 22

2Cl2 + 2H2O —> 4HCl + O2

Question 23

What is chlorine used for

Answer 23

To sterilise drinking water and water in swimming baths/pools

Question 24

Why has chlorine been replaced and what with

Answer 24

Calcium chlorate and because it is less hazardous