When salts dissolve in water
they become ionized. In other words, they break down to the ions
that formed them. For example a solution of common salt contains sodium
and chloride ions.
When two salts are mixed
together, different ions may react and result in new chemical
products. This especially happens when one of the possible
combinations are water insoluble and separate in the form of gas
or solids. Knowing how the ions react with each other can help
us predict and control the reactions in a direction that is
beneficial for us.