Hydrogen Halides

How can all hydrogen halides be made

Adding concentrated phosphoric acid to the solid ionic halide

Chemical equation for the reaction between sodium chloride and phosphoric acid

NaCl + H₃PO₄ → HCl + NaH₂PO₄

How else can hydrogen chloride be produced

By adding concentrated sulfuric acid to a salt containing chloride ions

Chemical equation for the reaction between sodium chloride and sulfuric acid

NaCl + H₂SO₄ → HCl + NaHSO₄

Why can’t hydrogen bromide or hydrogen iodide be produced using concentrated sulfuric acid

sulfuric acid is an oxidising agent and iodide and bromide ions are strong enough reducing agents to reduce sulfuric acid.

What do bromide ions reduce sulfuric acid to

sulfur dioxide

Chemical equation between sodium bromide and sulfuric acid

2NaBr + 2H₂SO₄ → Na₂SO₄ + Br₂ + SO₂ + H₂O

Ionic equation for the reaction between sodium bromide and sulfuric acid

H₂SO₄ + 2H⁺ + 2Br^- → Br₂ + SO₂ + 2H₂O

What do iodide ions reduce sulfuric acid to

hydrogen sulfide

Chemical equation for the reaction between sodium iodide and sulfuric acid

8NaI + 5H₂SO₄ → 4Na₂SO₄ + 4I₂ + H₂S + 4H₂O

Ionic equation for the reaction between sodium iodide and sulfuric acid

H₂SO₄ + 8H⁺ + 8I^- → 4I₂ + H₂S + 4H₂O

How does the thermal stability of hydrogen halides change down group 7 and why

• Decreases

• the strength of the hydrogen-halide bond gets weaker going down the group

• The halogen atoms get bigger, so the bonding electrons are further away from the nucleus and are shielded by more inner shells of electrons.

What occurs to the hydrogen halides upon heating

• Hydrogen fluoride and hydrogen chloride do not break down

• Hydrogen bromide breaks down a little

• Hydrogen iodide breaks down the most

What occurs to the hydrogen halides when they dissolve in water

They dissociate into hydrogen ions and halide ions

Which hydrogen halides are strong acids

Hydrogen chloride, hydrogen bromide, and hydrogen iodide

Which hydrogen halide is a weak acid

Hydrogen fluoride

How do hydrogen halide react with ammonia

• They donate an electron to ammonia so the positively charged ammonium ion is formed

• The positive ammonium ion and negative halide ion are electrostatically attracted to each other

Chemical equation between hydrochloric acid and ammonia

HCl_(aq) + NH_3(aq) → NH₄Cl_(aq)

Why don’t hydrogen fluoride and hydrogen chloride react with sulfuric acid

They are not strong enough reducing agents

What does hydrogen bromide reduced sulfuric acid to

sulfur dioxide

Chemical equation between hydrogen bromide and sulfuric acid

2HBr + H₂SO₄ → Br₂ + SO₂ + 2H₂O

What does hydrogen iodide reduce sulfuric acid to

Hydrogen sulfide

Chemical equation for the reaction between hydrogen iodide and sulfuric acid

8HI + H₂SO₄ → 4I₂ + H₂S + 4H₂O