Flashcards in Halogens Deck (23):
Pale yellow gas
Pale green gas
Dark red liquid
Fluorine in non-polar solvents and water
Chlorine in non-polar solvents and water
Pale green solution
Bromine in non-polar solvents and water
Iodine in non-polar solvents
Iodine in water
Insoluble but brown solution if excess KI
Why do the melting and boiling points of the halogens increase steadily down the group?
This is due to the increase in strength of the Van Der Waal's forces between the molecules, which results from the increasing number of electrons in the molecule and the increasing surface area of the molecule.
The ability of an atom to attract electrons in a covalent bond.
Why does electronegativity of the halogen atoms decreases down a group?
As the number of shells increases, the shielding increases and the electrons in the covalent bond are further from (and more shielded from) the nucleus. Therefore they are less strongly attracted to the nucleus and the electronegativity decreases.
NaCl + H2SO4
White fumes of HCl will be seen. The fumes will turn blue litmus paper red.
NaBr + H2SO4
Br2, H2O, SO2, NaHSO4
White fumes will be seen which turn blue litmus paper red. The red/orange colour of bromine will also be seen.
NaI + H2SO4
I2, H2O, S, H2S, NaHSO4
White fumes will be seen which turn blue litmus paper red. The purple colour of iodine vapour will also be seen and there a will be a smell of rotten eggs due to the presence of H2S.
Why is nitric acid added to silver nitrate solution?
Ensure that any carbonate or hydroxide ions, often found as impurities with halide ions, are removed as CO2 or water and so do not interfere with the precipitate.
Ammonia + AgCl
Ammonia + AgBr
If dilute ammonia is added to AgBr(s), there is no reaction but if concentrated ammonia is added then the precipitate dissolves.
Does not dissolve either in dilute or in concentrated ammonia.
Cl2(g) + H2O(l)
HCl(aq) + HClO(aq)
Why is chlorine used for sterilisation?
It is a mild oxidising agent and effective at killing bacteria without being harmful to humans. Chlorine is toxic to humans in anything other than very small doses, so care must be taken not to over-chlorinate the water supply.
Cl2(g) + 2OH-(aq)
Cl-(aq) + OCl-(aq) + H2O(l)