Double Displacement Reaction example
A. Silver nitrate reaction sodium chloride
AgNO3(aq) + NaCl(aq) ------> AgCl(s) + NaNO3(aq)
Uses: In preparation of silver chloride
B. Copper sulphate with hydrogen sulphide
CuS04(aq)+ H2S(g) ---------> CuS(s) + H2SO4(aq)
Copper sulphate react with hydrogen sulphide to form sulphuric acid. So copper sulphate is also called Blue vitriol. Blue because copper sulphate is blue and vitriol means sulphuric acid forming.
C. Reaction of an Acid with a Base
Sodium hydroxide with hydrochloric acid
NaOH(aq) + HCl(aq) ---------> NaCl(aq) + H2O(l)
2NaOH(aq) +H2SO4(aq) ------> Na2SO4(aq) +2H2O(l)
Easiest to remember.
But do not try to do it in home or lab without technician and bare hands as acids are highly corrosive.