Halide ions as reducing agents

Question 1

Chlorine reaction with sulfuric acid
Observations

Answer 1

HCl forms steamy white fumes

Question 2

Bromine reaction with sulphuric acid
Observations

Answer 2

Orange vapour from Br2 liquid
Choking gas from SO2

Question 3

Iodine reaction with sulphuric acid
Observations ( NO H2S )

Answer 3

Yellow solid (S)
Purple vapour from solid Iodine

Question 4

Iodine reactions with sulphuric acid
Observation ( With H2S)

Answer 4

Foul smelling H2S

Question 5

Chloride ion and conc H2SO4 equation

Answer 5

Cl- + H2SO4 —> HCl + HSO4-

Not a redox reaction, oxidation states remain the same
Acid-base reaction
Chloride ion too weak to reduce the sulphur so acts as a base

Question 6

Order of reducing power for halogens

Answer 6

I-
Br-
Cl-
F-
The larger the ion, the easier it is for it to lose an electron

Question 7

Reaction of Bromide ion with sulphuric acid

Answer 7

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

Sulphur reduced from 6+ to 4+
So this is a redox reaction
Bromine is a strong enough reducing agent

Question 8

Reaction of Iodide ion with sulphuric acid

Answer 8

6I- + H2SO4 + 6H+ —> 3I2 + S + 4H2O
Sulphur reduced from +6 to 0

8I- + H2SO4 + 8H+ —> H2S + 4H2O + 4I2
Sulphur reduced from +6 to -2

Question 9

Product of Cl- with H2SO4

Answer 9

HSO4-

Question 10

Product of Br- with H2SO4

Answer 10

SO2

Question 11

Product of I- with H2SO4
(Both reactions)

Answer 11

S
H2S