Non-redox Reactions/
Double Replacement Reactions
• OBJECTIVES:
– Distinguish between a non-redox and a redox
reaction.
– Recognize a double replacement (D.R.) reaction.
– Predict the products of a D.R. reaction.
– Predict whether a D.R. reaction will occur using
solubility rules or formation of gas or H2O(l)
(neutralization reaction).
– Complete and balance any D.R. that will occur.
– Write complete ionic and net ionic reactions.
Non-redox Reaction
• The oxidation number (charge) of the ions
involved does not change from the
reactant to the product side.
• Na2SO4(aq) + CaCl2(aq) CaSO4(s) + 2NaCl(aq)
• Redox: (the oxidation #’s are changing)
2 Fe + 3 Cl2  2 FeCl3
2 K(s) + FeCl2(aq)  Fe(s) + 2 KCl(aq)
Double Replacement
• Two things replace each other.
• Reactants must be two ionic compounds or
acids.
• Usually in aqueous solution
• Na2SO4(aq) + CaCl2(aq) 
• The positive ions change place.
• Na2SO4(aq)+ CaCl2(aq)Ca+2 SO42- + Na+1Cl-1
• Na2SO4(aq) + CaCl2(aq) CaSO4(s) + 2NaCl(aq)
To Double Replace
or
Not to Double Replace?
That is the Question?
• Will only happen if one of the products
– doesn’t dissolve in water and forms an
insoluble solid (s), precipitate (ppt).
– or is a gas that bubbles out.
– or water forms, H2O(neutralization reaction);
feel for heat.
Predicting the Precipitate
• Insoluble salt = a precipitate/solid (s)
–Solubility rules (see handout for
explanation)
CASH N GiAm
Solubility Rules Practice
Predict whether each of the following will be
soluble (aq) or an insoluble ppt (s):
• KCl
• Na2SO4
• CaSO4
• AgSO4
• Na2CO3
• MgS
Solubility Rules Practice
• KCl(aq)
• Na2SO4(aq)
• CaSO4(s)
• AgSO4(s)
• Na2CO3(aq)
• MgS(s)
Double Replacement
Two elements in reactants take the place of
each other
AB
+ CD  AD + CB
AgNO3(aq)+ NaCl(aq) AgCl(s) + NaNO3(aq)
Zn(OH)2(aq) + 2HCl(aq)  ZnCl2(aq) + 2H2O(l)
Double Replacement
• Will only happen if one of the products
– doesn’t dissolve in water and forms an
insoluble solid (s), precipitate (ppt).
– or is a gas that bubbles out.
– or water forms, H2O (neutralization
reaction); feel for heat.
Learning Check
Which of the following reactions is double
replacement?
A. 2Al(s) + 3H2SO4(aq)  Al2(SO4)3(aq) + 3H2(g)
B. Na2SO4(aq) + 2AgNO3(aq)Ag2SO4(s)+ 2NaNO3(aq)
C. 3C(s) + Fe2O3(s)  2Fe(g) + 3CO(g)
Complete & Net Ionic Equations
• Many reactions occur in water- that is, in
aqueous solution
• Many ionic compounds “dissociate”, or
separate, into cations and anions when
dissolved in water
• Now we can write a complete ionic
equation & Net ionic equation.
Complete Ionic Equation
• Example:
AgNO3(aq) + NaCl (aq)  AgCl (s) + NaNO3(aq)
1. this is the full equation (molecular equation)
2. now write it as an complete ionic equation
Anything (aq) will dissociate (separate into ions)
Ag+ + NO3- + Na+ + Cl-  AgCl(s) + Na+ + NO3-
Net Ionic Equation
Complete ionic equation:
Ag+ + NO3- + Na+ + Cl-  AgCl(s) + Na+ + NO3-
3. can be simplified by eliminating ions not
directly involved in making the reaction
happen (spectator ions) = net ionic equation
Ag+ + Cl-  AgCl(s)
Na+ and NO3- are spectator ions and are
removed in the net ionic equation.