Word Problems:
Predicting Products in Single and Double
Replacement reactions
Given the beginning of a chemical reaction, how
can you figure out what will be made, and if the
reaction will actually happen?
Steps to follow when writing your own
equations
 Determine the type of reaction (Synthesis,
Decomposition, Single Replacement, Double
Replacement or combustion)
 Use the reaction type information to predict the likely
products
 Check to make sure that each compound created has
balanced charges (zero net charge) .
Steps to follow when writing your own
equations – Continued
 Determine if the reaction will
happen
 If Single Replacement:
 A + BC  B + AC
 Determine which elements will
fight during the reaction. Two
cations will fight over one anion.
OR Two anions will fight over a
single cation.
 Zn + FeCl2  Fe + ZnCl2
 F2 + NaBr  NaF + Br2
 In the products, is the most
reactive element bonded and
the least reactive element
alone?
Steps to follow when writing your own
equations – Continued
 Determine if the reaction will happen
 If Double Replacement:
 AB + CD  AD + CB
 NaCl + AgNO3  NaNO3 + AgCl
 Switch the partners in the compounds. Make sure that you
bond the cation with a new anion. (The first ion bonds with the
last ion and the two inner ions bond)
 Is at least one of the products INSOLUBLE in water? Was a
covalent substance (like water) produced? Was a gas
created?
Solubility Table:
s= soluble
Ss= slightly soluble
i=insoluble
This table came from
http://en.wikipedia.org/wiki/Solubility_chart
Steps to follow when writing your own
equations – Continued
To sum up:
Single replacement reactions occur if the most active metal of the two is
bonded with a nonmetal OR the most active nonmetal of the two is
bonded with a metal at the end of the reaction.
Double replacement reactions occur if an insoluble ionic product, a gas
or a covalent substance like water is formed.
If it is any other type of reaction (synthesis, decomp or oxidation) you
may assume that it proceeds as written.
If the reaction will occur, then use coefficients to balance it.
If the reaction does not occur, then you can skip the balancing step.
Example Problem 1
Iron nails are placed in a solution of copper (II) chloride…
Fe + CuCl2 
Looks like Single Replacement
A + BC  AC + B
(Fe replaces the Cu+2 ion in the solution)
Fe + CuCl2  FeCl + Cu
Iron is more active than copper, so it should
be able to replace it in solution.
Iron takes either Fe+2 or Fe+3 charge. To
make it easy, let’s assume Fe+2 is created.
____Fe + ____CuCl2  _____FeCl2 + ____Cu
Example Problem 2
Lead (II) nitrate and potassium iodide solutions are mixed…
Pb(NO3)2 + KI 
Looks like Double Replacement
AB + CD  AD + CB
Lead will drop the nitrate and try to bond
with the iodine. Potassium will also switch
partners
Pb(NO3)2 + KI  PbI2 + KNO3
PbI2 = INSOLUBLE
KNO3 = Soluble
Since one of the products is insoluble, the
reaction will occur
___Pb(NO3)2 + ___KI  ___PbI2 + ___KNO3
Example Problem 3
Potassium iodide and sodium carbonate solutions are mixed…
KI + Na2CO3
Looks like Double Replacement
AB + CD  AD + CB
Potassium will drop the iodide ion and try to
bond with the carbonate. Sodium will also
switch partners
KI + Na2CO3 NaI + K2CO3
Both products are soluble ionic compounds.
No gas was created. No reaction occurred.
There is no need to balance it. The reaction
does not occur.
Example Problem 4
A solution of sodium iodide is mixed with chlorine gas dissolved in water…
NaI + Cl2 
Looks like Single Replacement
AB + C  AC + B
(Chlorine will attempt to replace the iodine)
NaI + Cl2  NaCl + I2
Chlorine is more active than iodine so the
reaction will proceed.
____NaI + _____Cl2  _____NaCl + _____I2
Try these two problems on your own
Practice Problem A
Practice Problem B
 Barium nitrate and sodium
carbonate solutions are mixed…
 A copper metal strip is placed in
sulfuric acid…
Pause the video and try these two problems on your own