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How do I write a net ionic equation for an aqueous double displacement reaction?

What are the products and the net ionic equation for the reaction between H2C2O4 and Pb(NO3)2?
Rickesh Kotecha (grade 11)

To predict the products of a double displacement reaction:

  1. Identify the ions. Oxalic acid contains H+ and C2O42-ions; lead(II) nitrate contains Pb2+ and NO3- ions.
  2. Swap the ions. The H+ goes with the NO3- to form HNO3 on the product side. The C2O42-goes with the Pb2+ to form PbC2O42-on the product side.
  3. Classify the products. At least one of the products must be either a) a weak electrolyte or b) an insoluble salt, or no reaction occurs. In your reaction, the lead(II) oxalate is an insoluble salt, and the nitric acid is a soluble strong acid.
To write the net ionic equation:
  1. Balance the equation.
    H2C2O4(aq) + Pb(NO3)2(aq) rightarrow PbC2O4(s) + 2 HNO3(aq)
  2. Break all strong electrolytes into ions. In your reaction, oxalic acid is NOT a strong electrolyte. You'll have to carry it over into the ionic equation unchanged. You also can't consider the lead(II) oxalate a strong electrolyte because it remains a solid:
    H2C2O4(aq) + Pb2+(aq) + 2 NO3-(aq) rightarrow PbC2O4(s) + 2 H+(aq) + 2 NO3-(aq)
    This equation is called a "complete ionic equation" or "total ionic equation" because all the strong electrolytes are written as ions.
  3. Eliminate spectator ions. These are ions that appear on both sides of the equation (and so, are unchanged by the reaction). The nitrate ion is the only spectator in this reaction.
    H2C2O4(aq) + Pb2+(aq) rightarrow PbC2O4(s) + 2 H+(aq)
    This last equation is the net ionic equation.

Author: Fred Senese senese@antoine.frostburg.edu



General Chemistry Online! How do I write a net ionic equation for an aqueous double displacement reaction?

Copyright © 1997-2010 by Fred Senese
Comments & questions to fsenese@frostburg.edu
Last Revised 02/15/10.URL: http://antoine.frostburg.edu/chem/senese/101/reactions/faq/ionic-equation-h2c2o4-pbno32.shtml