What is a spectator ion?

A spectator ion is an ion that exists as both a reactant and a product in a chemical equation.

Consider the reaction

NaCl(aq)+AgNO3(aq)→AgCl(s)+NaNO3(aq)

The ionic equation is:

Na+(aq)+Cl−(aq)+Ag+(aq)+NO−3(aq)→AgCl(s)+Na+(aq)+NO−3(aq)

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The Na+ and NO−3 ions are spectator ions because they remain unchanged on both sides of the equation. They just "watch" the other ions react, hence the name.

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We usually cancel the spectator ions from each side of an ionic equation to form anet ionic equation:

Na⁺(aq)+Cl−(aq)+Ag+(aq)+NO₃⁻(aq)→AgCl(s)+Na⁺(aq)+NO₃⁻(aq)

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Cl−(aq)+Ag+(aq)→AgCl(s)

EXAMPLE:

Identify the spectator ions and write the net ionic equation for the reaction:

HCl(aq)+NaHCO3(aq)→NaCl(aq)+H2O(l)+CO2(g)

SOLUTION:

Ionic Equation:

H+(aq)+Cl−(aq)+Na+(aq)+HCO−3(aq)→Na+(aq)+Cl−(aq)+H2O(l)+CO₂(g)

The spectator Ions are Cl− and Na+.

Net Ionic Equation:

H+(aq)+Cl⁻(aq)+Na⁺(aq)+HCO−3(aq)→Na⁺(aq)+Cl⁻(aq)+H2O(l)+CO2(g)

https://www.youtube.com/watch?v=vbx5nfAiBlMH+(aq)+HCO−3(aq)→H2O(l)+CO2(g)