Double Replacement Reactions: A reaction in which two ionic compounds exchange their ions to form a non-ionic (molecular) compound product either as (1) a solid insoluble precipitate, (2) a gas or (3) a molecular compound, the formation of which drives the reaction to completion.
A) Fe2O3(s) + 3CO(g) -> 2Fe(s) + 3CO2(g)
B) 2H2(g) + O2(g) -> 2H2O(l)
C) 2HgO(s) -> 2Hg(l) + O2(g)
D) NaCl(aq) + AgNO3(aq) -> AgCl(s) + NaNO3(aq)