Conversely,
if a solution of sodium chloride and magnesium nitrate were to be mixed,
no change would be observed since both sodium nitrate and magnesium
chloride (potential products) are soluble.
That
is,
Na+(aq) + Cl-(aq) + Mg2+(aq) + 2NO3-(aq) ® Na+(aq) + Cl-(aq) + Mg2+ (aq) + 2NO3-(aq)
(NaCl(aq) + Mg(NO3)2 (aq))
which is essentially no reaction.
For an ion-exchange reaction to occur, one
of the products must be insoluble.