Complete and Net Ionic Equations in GOB Chemistry

Complete and Net Ionic Equations

Introduction to Complete Ionic Equations

Complete ionic equations are used to represent aqueous compounds as dissociated ions in chemical reactions. This approach is essential for understanding the behavior of substances in solution, especially in precipitation, acid-base, and redox reactions.

• Complete ionic equations show aqueous compounds as dissociated ions.

• Solids, liquids, and gases never break up into ions in these equations.

• The complete ionic equation is derived from the molecular equation by distributing the coefficient of each compound to determine the correct number of ions.

Example: Converting a Molecular Equation to a Complete Ionic Equation

• Molecular Equation: $3\text{CaBr}_2 (aq) + 2\text{Li}_3\text{PO}_4 (aq) \rightarrow 6\text{LiBr} (aq) + 1\text{Ca}_3\text{PO}_4 (s)$

• Complete Ionic Equation: $3\text{Ca}^{2+} (aq) + 6\text{Br}^- (aq) + 6\text{Li}^+ (aq) + 2\text{PO}_4^{3-} (aq) \rightarrow 6\text{Li}^+ (aq) + 6\text{Br}^- (aq) + 1\text{Ca}_3\text{PO}_4 (s)$

Additional info: The solid product (precipitate) does not dissociate and remains as a compound in the equation.

Net Ionic Equations

Net ionic equations focus on the ions and molecules directly involved in the chemical change, omitting spectator ions that do not participate in the reaction.

• Spectator ions are present in solution but do not take part in the actual chemical reaction.

• Net ionic equations are derived by removing spectator ions from the complete ionic equation.

Example: Writing Net Ionic Equations

• Given Reactants: $\text{(NH}_4)_2\text{SO}_4 (aq) + \text{CaCl}_2 (aq)$

• Steps:

  1. Write the balanced molecular equation.

  2. Convert to the complete ionic equation by dissociating all aqueous compounds into their ions.

  3. Identify and cancel out the spectator ions.

  4. Write the net ionic equation with only the ions and compounds that participate in the reaction.

Additional info: The net ionic equation highlights the actual chemical change occurring in the reaction.

Stepwise Approach to Ionic Equations

• STEP 1-4: Follow the steps to determine the balanced molecular equation.

• STEP 5: Break up only the aqueous compounds into their respective ions.

• STEP 6: Cancel out the spectator ions from the complete ionic equation to isolate the net ionic equation.

Practice Problems

Application of Net Ionic Equations

• Practice: Provide the net ionic equation for the reaction between Copper (II) Bromide and Lithium Hydroxide.

• Practice: Identify which reagent could be used to separate two anions from a solution containing magnesium nitrate and cesium hydroxide.

  • a) NH4CN

  • b) NaCl

  • c) KNO3

  • d) ZnBr2

  • e) CsBrO3

• Practice: Identify which reagent could be used to separate two cations from a solution containing Lead (IV) acetate and cesium permanganate.

  • a) Sr(NO3)2

  • b) Tc2H4O2

  • c) K2S

  • d) NaClO4

Key Terms and Definitions

• Molecular Equation: Shows all reactants and products as compounds.

• Complete Ionic Equation: Shows all strong electrolytes as ions.

• Net Ionic Equation: Shows only the species that actually participate in the reaction.

• Spectator Ions: Ions that do not participate in the chemical reaction.

Summary Table: Types of Equations

Type of Equation	Features	Example
Molecular Equation	All reactants and products shown as compounds	$\text{AgNO}_3 (aq) + \text{NaCl} (aq) \rightarrow \text{AgCl} (s) + \text{NaNO}_3 (aq)$
Complete Ionic Equation	All strong electrolytes shown as ions	$\text{Ag}^+ (aq) + \text{NO}_3^- (aq) + \text{Na}^+ (aq) + \text{Cl}^- (aq) \rightarrow \text{AgCl} (s) + \text{Na}^+ (aq) + \text{NO}_3^- (aq)$
Net Ionic Equation	Only species involved in the reaction are shown	$\text{Ag}^+ (aq) + \text{Cl}^- (aq) \rightarrow \text{AgCl} (s)$