Complete Ionic Equations: Videos & Practice Problems

In chemistry, understanding the transition from a molecular equation to a complete ionic equation is crucial for analyzing reactions in aqueous solutions. A molecular equation presents all reactants and products in their molecular forms, including solids, liquids, and gases, while a complete ionic equation breaks down only the aqueous compounds into their constituent ions.

When dealing with complete ionic equations, it is essential to recognize that only aqueous compounds dissociate into ions. Solids, liquids, and gases remain intact and do not break apart. To determine whether a compound is aqueous, solubility rules are applied, which help identify which substances will dissolve in water and form ions.

To derive a complete ionic equation from a molecular equation, one must distribute the coefficients of each compound correctly. This ensures that the number of ions represented reflects the actual quantities involved in the reaction. For example, if a molecular equation shows a compound with a coefficient of 2, this indicates that two moles of that compound will dissociate into ions, effectively doubling the number of ions in the complete ionic equation.

In summary, the complete ionic equation provides a clearer picture of the chemical processes occurring in solution by illustrating how aqueous compounds dissociate into ions, while maintaining the integrity of solids, liquids, and gases. This understanding is fundamental for predicting the outcomes of chemical reactions and for further studies in solution chemistry.

To convert a molecular equation into a complete ionic equation, it is essential to recognize which compounds can dissociate into ions. In this case, we have the reaction of 3 moles of calcium bromide (CaBr₂) aqueous with 2 moles of lithium phosphate (Li₃PO₄) aqueous, resulting in the formation of 6 moles of lithium bromide (LiBr) aqueous and 1 mole of calcium phosphate (Ca₃(PO₄)₂) solid.

Only the aqueous compounds will dissociate into their respective ions. Therefore, we will break down the calcium bromide, lithium phosphate, and lithium bromide into their ions, while the calcium phosphate remains intact as a solid.

Starting with calcium bromide, the dissociation yields:

3 CaBr₂ → 3 Ca²⁺ (aq) + 6 Br^- (aq)

Next, for lithium phosphate, the dissociation gives:

2 Li₃PO₄ → 6 Li⁺ (aq) + 2 PO₄^3- (aq)

Finally, lithium bromide dissociates as follows:

6 LiBr → 6 Li⁺ (aq) + 6 Br^- (aq)

Since calcium phosphate is a solid, it does not dissociate and remains as:

1 Ca₃(PO₄)₂ (s)

Combining all these components, the complete ionic equation is:

3 Ca²⁺ (aq) + 6 Br^- (aq) + 6 Li⁺ (aq) + 2 PO₄^3- (aq) → 6 Li⁺ (aq) + 6 Br^- (aq) + 1 Ca₃(PO₄)₂ (s)

In summary, when converting to a complete ionic equation, remember to only break apart aqueous compounds and distribute coefficients to the respective ions formed.

A net ionic equation is a simplified representation of a chemical reaction that highlights the ions directly involved in the reaction while omitting the spectator ions. Spectator ions are those that appear unchanged on both sides of the equation, meaning they do not participate in the actual chemical change. To derive a net ionic equation, one must first start with the molecular equation, which represents the overall reaction in terms of the reactants and products.

The next step is to convert the molecular equation into a complete ionic equation. This involves breaking down all soluble ionic compounds into their respective ions. Once the complete ionic equation is established, the spectator ions can be identified and removed, leading to the formation of the net ionic equation. This process emphasizes the ions that are actively participating in the reaction, providing a clearer understanding of the underlying chemical processes.

In summary, the pathway to obtaining a net ionic equation involves:

1. Starting with the molecular equation.
2. Converting it to the complete ionic equation by dissociating soluble ionic compounds.
3. Removing the spectator ions to arrive at the net ionic equation.

This method is essential for analyzing reactions in aqueous solutions, where the behavior of ions is crucial to understanding the reaction dynamics.

In a reaction between ammonium sulfate and calcium chloride, we can derive both the molecular equation and the complete ionic equation. The molecular equation begins with the reactants:

Ammonium sulfate: (NH₄)₂SO₄ and Calcium chloride: CaCl₂.

When these compounds react, they form ammonium chloride and calcium sulfate. The balanced molecular equation is:

(NH₄)₂SO₄ (aq) + CaCl₂ (aq) → 2 NH₄Cl (aq) + CaSO₄ (s)

Next, we break down the aqueous compounds into their ionic forms for the complete ionic equation. Ammonium sulfate dissociates into 2 ammonium ions (NH₄⁺) and 1 sulfate ion (SO₄^2-), while calcium chloride dissociates into 1 calcium ion (Ca²⁺) and 2 chloride ions (Cl^-):

2 NH₄⁺ (aq) + SO₄^2- (aq) + Ca²⁺ (aq) + 2 Cl^- (aq) → 2 NH₄Cl (aq) + CaSO₄ (s)

In this complete ionic equation, we can identify the spectator ions, which are ions that do not participate in the actual precipitation reaction. Here, the ammonium ions and chloride ions are spectator ions. By removing these from the equation, we arrive at the net ionic equation:

SO₄^2- (aq) + Ca²⁺ (aq) → CaSO₄ (s)

This net ionic equation highlights the essential reaction occurring, which is the formation of solid calcium sulfate from the sulfate and calcium ions in solution. Understanding the process of deriving the molecular equation, complete ionic equation, and net ionic equation is crucial for analyzing chemical reactions and predicting the formation of precipitates.