high concentration, the equilibrium involves the removal of fluoride ions is important. Since it affects the dissociation of hydrogen fluoride and increases and hydrogen ion concentration Several stable salts NaHF , KHF and NH HF are known. The other hydrogen halides do not form hydrogen dihalides. Hydrohalic acid shows typical acidic properties.
They form salts with acids, bases and reacts with metals to give hydrogen. Moist hydrofluoric acid (not dry) rapidly react with silica and glass. SiO + 4HF SiF + 2H O Na SiO + 6HF Na SiF + 3H O Oxidation: Hydrogen iodide is readily oxidised to iodine hence it is a reducing agent. 2HI H I + 2e ⇀ ↽ Acidic solution of iodides is readily oxidised.
A positive result is shown by liberation of iodine which gives a blue-black colouration with starch. XII XII - - - - Hydrogen bromide is more difficult to oxidise than HI. HBr reduces slowly H SO into SO 2HBr + H SO H O Br + SO But hydrogen iodide and ionic iodides are rapidly reduced by H SO into H S and not into SO . 8HI + H SO H O 4I + H S Reducing property of hydrogen iodide can be also explained by using its reaction with alcohols into ethane.
It converts nitric acid into nitrous acid and dinitrogen dioxide into ammonium. Hydrogen chloride is unaffected by concentrated sulphuric acid but affected by only strong oxidising agents like MnO , potassium permanganate or potassium chloride. To summarize the trend, Property Order Reactivity of hydrogen Decreases from fluorine to iodine Stability Decreases from HF to HI Volatility of the hydrides HF < HI < HBr < HCl Thermal stability HF > HCl > HBr > HI Boiling point HCl < HBr < HI < HF Acid strength Increases from HF to HI . .
Inter halogen compounds: Each halogen combines with other halogens to form a series of compounds called inter halogen compounds. In the given table of inter halogen compounds