Halides

Question 1

What products are formed when I- reduces H2SO4? + equations + observations

Answer 1

1) H2SO4 + 2H+ + 2I- -> SO2 + I2 + 2H20 (SO2 is a choking gas with pungent odour)

2) H2SO4 + 6H+ 6I- -> S + 3I2 + 4H20 (S is yellow solid)

3) H2SO4 + 8H+ + 8I- -> H2S + 4I2 + 4H20 (H2S smells of rotten egg)

Question 2

What’s the equation and observation for when I- is oxidised

Answer 2

H2SO4 + 2H+ + 2I- -> SO2 + I2 + 2H20
Purple fumes/black solid

Question 3

What’s the equations and observations for all 3 halide ions in a acid base reaction

Answer 3

H2SO4 + KI —> HI + KHSO4
H2SO4 + KBr—> HBr + KHSO4
H2SO4 + KCl —> HCl + KHSO4
white fumes

Question 4

What is the strongest and weakest reducing agent

Answer 4

Strongest - I-
Br-
Weakest - Cl-

Question 5

Why is I- the best reducing agent

Answer 5

• halide ion loses an electron when it reduces H2SO4
• the bigger the halide ion the easier it is to lose an electron as it is bigger and has more shielding

Question 6

What is the equation and observation for Br- reducing H2SO4 and getting oxidised

Answer 6

H2SO4 + 2H+ + 2Br- —> Br2 + SO2 + 2H20
Oxidation of Br- : orange fumes
Reduction of H2SO4: colourless gas