Group 7 Reactions Flashcards
(24 cards)
Are all nitrates soluble or insoluble
Soluble
How to identify the halide
Add a few drops of dilute nitric acid and a few drops of silver nitrate solution and see what colour it turns due to coloured precipitates forming, can be difficult to distinguish so add dilute/conc ammonia solution
What colour does precipitate is formed when silver nitrate is added to chlorine
White
What colour precipitate is formed when silver nitrate is added to bromine
Cream
What colour precipitate is formed when silver nitrate is added to iodine
Yellow
How to distinguish between the three similar colours further
Silver chloride dissolves in dilute ammonia, silver bromide dissolves in concentrated ammonia and silver iodide does not dissolve
How does sulphuric acid react with halide salts
Acts as either an oxidising agent by removing electrons from halide ions converting them into the diatomic gas (for bromine and iodine) or as an acid where it gives hydrogen ions to the halide and displaces its salt (for fluorine and chlorine as these are strong oxidising agents)
What is formed when hydrogen halides react with ammonia gas
React to produce corresponding ammonium salt(white solid) and white smoke eg HCl+NH3—> NH4Cl
Formula for bleach
NaClO
Reaction between chlorine and cold aqueous sodium hydroxide
Cl2 + 2NaOH ——>NaClO(bleach) + NaCl + H2O
Reaction between chlorine and hot aqueous sodium hydroxide and why it’s different
3Cl2 + 6NaOH —->NaClO3 + 5NaCl + 3H2O
Chlorine oxidised further from 0 to +5 instead of on cold where it is to +1
Are hydrogen halide gases soluble
Yes
Reaction of chlorine with cold water
Cl2 + H2O ——>ClO-(chlorate(I) ions) + Cl- + 2H+
Reaction of sodium fluoride and chloride with sulfuric acid and why it stops there
NaF/Cl + H2SO4——-> NaHSO4 + HF/Cl (misty fumes)
- the hydrogen halide does not further reduce the sulfuric acid as it is not a strong enough reducing agent
How to identify hydrogen halides
Misty fumes
How to identify sulfur dioxide
Choking fumes
Two step reaction of sodium bromide with sulfuric acid and why are there two steps
NaBr + H2SO4 ——-> NaHSO4 + HBr
2HBr + H2SO4 ——-> Br2(reddish-brown gas) + SO2 + 2H2O
-two steps as hydrogen bromide is a strong enough reducing agent to reduce the sulfuric acid to form sulfur dioxide (choking gas)
Four step reaction of sodium iodide with sulfuric acid and why three steps
NaI + H2SO4 ——> NaHSO4 + HI
2HI + H2SO4 ——> SO2 + I2 + 2H2O
6HI + H2SO4 ——> 3I2 + S (s) + 4H2O
6HI + SO2 ——> H2S + 3I2 + 2H2O
-iodide ions have strongest reducing power so can further reduce the sulfur dioxide
How to identify hydrogen sulfide and what is its formula
H2S, toxic gas which smells of rotten eggs
Reactions of hydrogen halides with water
-form strong acids as they dissociate to release their halide ions and hydrogen ions and these hydrogen ions form a hydronium ion with water resulting in strong acidic solution
Eg HCl + H2O ——> Cl- + H3O+
What are hydrogen halides in solution
Strong acids
Colour of halogens in water
Fluorine-pale yellow
Chlorine- greenish yellow
Bromine- reddish brown
Iodine- brown
Colour of halogens in organic solvent
Fluorine- yellow
Chlorine- green
Bromine- orange-yellow
Iodine- purple
Why does HBr form misty fumes when in moist air
Dissolves in water in air to form droplets of hydrobromic acid
