Sometimes the full equation of a reaction and the net ionic equation balance out differently. If that is the case, which is the correct one to use?

For instance, in the reaction between a solution of iron(III) chloride and lead(II) nitrate, you get the following for the complete equation:

2FeCl3 + 3Pb(NO3)2 → 3PbCl2 + 2Fe(NO3)2

However, when you use the net ionic equation, you get

6Cl- + 3Pb(2+) → 3PbCl2

However, this can be reduced to

2Cl- + Pb(2+) → PbCl2

This doesn't match with the complete equation.

If the net ionic equation does not match the complete equation, which one should you use? Or is it ok to use both?

  • $\begingroup$ The complete equation is not balanced as written $\endgroup$ – Buck Thorn Nov 20 '18 at 13:43

There is a time and a place for both the complete equation (which is missing 2 Fe(NO3)3, btw) and the NIE. It sort of depends on what you are discussing / doing.

As far as the question is it ok to use 2Cl- + Pb(2+) → PbCl2, even though the coefficients are different, yes. Since the iron and nitrate are acting as spectator ion, they're not important to the NIE. So, don't sweat it when the NIE looks different from the complete equation. The chloride ions and the lead (II) ions could have come from (e.g.) NaCl and Pb(ClO3)2. That's one of the points of NIE's: they focus on only the ions you need to worry about for the (very) specific reaction.

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