Chlorine is used to in swimming pools and drinking water to kill bacteria.
Iodine is used as an antiseptic because it will kill the germs on the skin without damaging it.
C3.13 Physical properties of halogens
The colour of the Halogens changes from a lighter colour
to a dark colour as we go down the group and the melting and boiling points
increase as you go down the group. Fluorine at the top of the group is
a yellow gas
This changes to a yellow-green
gas for chlorine, a red liquid for
bromine and finally black solid for iodine at the bottom of the
group.
C3.14 Reactions of halogens with metals
Metal + Halogen --> Metal Halide
Iron reacts slowly with iodine to form iron II iodide.
Iron reacts faster with bromine to form iron III bromide.
Iron reacts with chlorine
reacts even faster to form iron III chloride.
See
animation of iron + halogen reactions.
Other metals like sodium also react.
sodium + chlorine ---> sodium chloride
C3.15 The reaction of halogens with hydrogen
Hydrogen reacts with halogens to form hydrogen halides. E.g.
Hydrogen + chlorine ---> hydrogen chloride
H2(g) +Cl2(g) --> 2HCl(g)
(a hydrogen halide)
Hydrogen halides are very soluble in water. The gas hydrogen chloride forms hydrochloric acid when
it dissolves in water. Other hydrogen halides like hydrogen bromide, HBr and
hydrogen iodide, HI also dissolve
to form acid solutions. An acid solution has a pH less than 7 e.g.
1. An acid turns universal indicator red.
Task C3.15
C3.16 Displacement reactions
Halogens like chlorine are very reactive and displace
less reactive halogens like bromine from halides like bromides.
Potassium bromide + chlorine ---> potassium chloride +
bromine
2KBr(aq) + Cl2(aq) --> 2KCl(aq) + Br2(aq)
2Br-(aq) + Cl2(aq)
--> 2Cl-(aq) + Br2(aq)
Chlorine and bromine also react with potassium iodide showing that the order of
reactivity is: Chlorine > bromine > iodine
Task C3.16
C3.17 Uses of halogens and halides
Fluorine compounds (fluorides) are put into toothpaste and some drinking
water supplies. Fluorides join with tooth enamel and make teeth resist
attack by acid which
prevents tooth decay.
Chlorine is used to in swimming pools and drinking water to kill bacteria.
Iodine is used as an antiseptic because it will kill the germs on the skin
without damaging it.