Activity series, Solubility

If we want to figure out that the Single replacement have reaction or not, we can always look for    the Activity series .



Ex.

Mg + CoCl2 >  MgCl2 + Co        (Reaction, As Mg has higher activity than Co)

Sn   + NiO    >  SnO     + Ni         (No reaction, Although the equation is completed,Sn has lower activity than Ni)

For Double Replacement, we can look for the SOLUBILITY.

Soluble can refer to (aq) (l) ; INsoluble means (s) < solid

As a Double Replacement is usually have (s) < solid as a product,  which means in the right side or product side of the equation, there is usually have at least one (s) or 2 (s), if so, then it'll have reaction.