most people will be able to tell you
what salt is
a bunch of clear granules that we use to
make our food taste better
well that's certainly true of table salt
sodium chloride but did you know that
salt actually refers to a very large
family of compounds many with quite
different properties and uses to table
salt
let's start with what a salt is it's an
ionic compound made up of one or more
positively charged cations and
negatively charged anions an ionic
compound is electrically neutral watch
this video if you'd like a refresher on
this concept
the cation tends to be a metal and in
many common examples is one from group
one or two of the periodic table the
anion is commonly a halide from group
seven or a member of group six
salts made like this are called
inorganic salts but this is not always
the case
the ions can be polyatomic that is made
up of more than one atom a common
example of this would be ammonium salts
you might wonder if all salts are small
transparent crystals just like table
salt
certainly not salts come in many
different colors
sodium chromate
is yellow
potassium permanganate is purple
and iron disulfide is shiny and metallic
in fact it's a mineral commonly called
fool's gold
another common mistake is to think that
all salts taste well salty again this is
wrong some taste bitter and some even
taste sweet like lead diacetate
unfortunately it's also poisonous
here's another more complicated salt
with nitrogen in the cation
it's part of a family called the
diazonium salts which are all brightly
coloured can you think what they might
be used for pause and have a thing then
resume
the answer is they're used for dye
pigments to colour our clothes
if you ever get the chance to enjoy some
fireworks the bright colours you can see
are produced by burning the salts of
various metals
you might recall learning that an acid
plus a base gives you a salt and water
and that's quite right for an inorganic
salt
here's the classic reaction for making
sodium chloride hydrochloric acid plus
sodium hydroxide equals sodium chloride
and water
here's the thing though hydrochloric
acid sodium hydroxide
and sodium chloride are all water
soluble and dissolve to form clear
solutions so the challenge is can you
think how you would monitor this
reaction to make sure it is actually
happening pause and have a thing then
resume
here's the answer you would monitor the
ph of the solution while you add the
base gradually to the acid by titration
you could use an indicator like methyl
orange
it's an orangey red color in acidic
solutions but turns yellow when they are
turned basic
the ph would start at around one to two
but as the acid is neutralized and the
salt and water formed it would start to
rise
once neutralized the final step is to
evaporate the water leaving the salt
crystals behind on the sides of your
reaction vessel
now while this technique is good to know
we wouldn't ever have to create table
salt this way in industry because nature
does the chemistry for us and sodium
chloride can either be mined from the
ground or evaporated from seawater
and don't think this is the only way of
making salts either they can also be
formed by introducing a metal to an acid
as in this reaction
or by combining a metal and a non-metal
like a halogen as in this reaction
all of these salts are soluble in water
but some salts are highly insoluble and
some are what we call sparingly soluble
meaning only a small amount can dissolve
and the rest stays as crystals salts
made with sodium potassium and ammonium
cations and those made with nitrate
anions are all water soluble
but most salts made with carbonate and
ions are water insoluble
salts dissolved in solution have an
important property the ability to
conduct electricity and we call them
electrolytes