Reactions of sodium halides with concentrated sulfuric acid

Give the equation of the initial chemical reaction that occurs when concentrated sulfuric acid is added to any sodium halide.

NaX + H₂SO₄ → NaHSO₄ + HX

X= halogen i.e. Cl, Br or I

This reaction produces steamy fumes of HX gas.

Why does HBr and HI react further with concentrated sulfuric acid, whilst HCl doesn’t?

Bromide and iodide have lower electrode potential values, so it is easier to oxidise these halides.

Sulfuric acid is a very strong…

Oxidising agent.

What product is formed when HBr is oxidised by sulfuric acid?

2HBr (s) + H₂​SO₄​(c) → SO₂ ​+ Br_2​(g) + HBr(g)

HBr can be oxidised by sulfuric acid to form Br₂ as orange fumes.

During the process, the sulfur in NaHSO₄ is reduced from +6 and forms SO₂ ​ with an oxidation state of +4. The bromide is a strong enough reducing agent.

What product is formed when HI is oxidised by sulfuric acid?

NaI(s) + H₂​SO₄ ​(c) → NaHSO₄​(s) + HI(g)

HI can be oxidised by sulfuric acid to form I₂ as black/brown solid or purple fumes.

During the process, the sulfur in Na SO₄ is reduced from +6, and forms SO₂ with an oxidation state of +4, S as a yellow solid (oxidation state 0) and , H₂S as a gas which smells of rotten eggs (oxidation state -2).

The iodide is a 1 much stronger reducing agent and can reduce sulfur from +6 to -2.