Page 6 - Analytical Chemistry 1

Molecular and ionic equations

(i) Molecular equation is a chemical equation in which the reactants and
products are written as if they were molecular substances, even though
they may actually exist in solution as ions. It closely describes what
you actually do in the laboratory or in an industrial process.

Ca(OH)2 (aq) + Na2CO3 (aq) ⎯→ CaCO3 (s) + 2NaOH (aq)

(ii) Complete ionic equation is a chemical equation in which strong
electrolytes (such as soluble ionic compounds) are written as separate
ions in solution. The purpose of such an equation is to represent each
substance by its predominant form in the reaction mixture.
• If the substance is a soluble ionic compound, it dissolves as
individual ions (so it is a strong electrolyte) and you represent the
compound as separate ions.
• If the substance is a weak electrolyte, it is present in solution
primarily as molecules, so you represent it by its molecular
formula.
• If the substance is an insoluble ionic compound, you represent it by
the formula of the compound, not by the formulas of the separate
ions in solution.

Then,

Ca2+ (aq) + 2OH- (aq) + 2Na+ (aq) + CO32- (aq) → CaCO3(s) + 2Na+ (aq)
+ 2OH- (aq)

(iii) Net ionic equation is an ionic equation from which spectator ions
have been cancelled. A spectator ion is an ion in an ionic equation that

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